Herbaceous Ornamental Plants and Aquatic Gardening

Please Note: All recommendations are for central Maryland.  Time frames shift two weeks earlier in Southern Maryland and the Eastern Shore and two weeks later for Western Maryland.  Check publications for further information.

JANUARY

• Clean up and compost dead hosta leaves and other plant parts, but leave the flower heads of perennials, like tickseed, purple coneflower and black-eyed Susans to provide nutritious seeds for birds this winter. Perennials and ornamental grasses can also provide needed cover for over-wintering birds. See our page on Attracting Wildlife.

• Plant any leftover bulbs in the garden as long as the soil can be worked. Follow package instructions for planting depth and spacing. The site should be sunny and the soil should be well-amended with organic matter. Fertilize the planting area with a balanced fertilizer containing nitrogen, phosphorous, and potassium. It is not necessary to apply bonemeal. Daffodil bulbs are less likely to be eaten or disturbed by rodents and squirrels than most other bulbs. Tulip bulbs can be protected from animal pests by covering them with a wire mesh like chicken wire.

• Consider planting groundcovers this spring where grass won’t grow, where you have heavy shade, tree root problems or steep slopes. Select plants based on the amount of sun they require. Good choices include periwinkle, liriope, epimedium, sweet woodruff and ajuga or bugleweed. Groundcovers are also useful as a border around buildings and garden beds. However, do not plant these rapid growers near property lines or woodlands. (HG 89 Ground Covers)

• Fallen tree leaves that pile up and mat around groundcovers can encourage foliar diseases in the spring. This is a good time to prune out damaged leaves and inspect wintercreeper and Japanese euonymus foliage (photo) for scale problems (HG 48). Scale insects can be controlled with a dormant oil spray. Be sure that temperatures are expected to remain above freezing for a 24 hour period after spraying.

• Aquatic Gardening - If you haven’t laid a chicken wire screen over your pond you’ll need to remove leaves that are floating in the pond. Stop feeding your fish. They cannot metabolize food easily during cold weather. Clean up pond statuary, fountains and other concrete or plastic pond features and cover these items with plastic to prevent snow and ice damage. Bring pumps and filters indoors. Stock tank heaters can be purchased and installed to keep your pond from freezing over. This will promote gas exchange between air and water and help your fish survive the winter.

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FEBRUARY

• Avoid the temptation to start seeds too early. Check seed packets for detailed information on starting various types of flowers. Some slow growing flowers like begonia, geraniums, and impatiens should be started 12-14 weeks before the last expected frost. Most other annuals are started about 6-8 weeks before the last frost date. Do not depend on window sill light to grow these seedlings. Annual flower plants are best started and grown indoors under cool, white fluorescent lights. The tubes should be lit for 14-16 hours per day and kept only 1-2 inches from the top of the young seedlings. Don’t over-water, and keep the temperature at 70-75 degrees F. during the day and 65 degrees F. at night.

• If you did not get your spring bulbs planted, do so as soon as the ground thaws. Select only the best quality. Many of the bulbs will have deteriorated over winter storage. They may still bloom this year but much later than normal.
  Established spring bulbs are slowly emerging this month. They are first to emerge in sunny locations or south facing slopes. Gardeners often worry about them when there is still some very cold weather ahead. Exposed leaves may experience a little tip browning by very cold temperatures, but the spring flower display will not be diminished.

• Continue to leave the large seed heads of black-eyed Susans, coneflowers and other perennials for birds to feed on over the winter. Remaining stems will be cut down next month, but for now the birds will enjoy these seeds.

• While browsing through seed catalogs consider growing something this year different like annual vines: cardinal climber, hyacinth bean, morning glory, etc. to cover fences, gazebos and trellises. Check seed catalogs for improved varieties, choosing an “All America” selection is always a good bet. Start these seeds indoors under fluorescent lights 6-8 weeks before the last frost, which is around May 10 in Central Maryland. 

• Curious about Spring frost dates in your area?  See our Spring Frost/Freeze table for more information. 
  

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MARCH

• Starting Seeds Indoors – Many types of annual flower plants can be started indoors this month. Generally, most are started 5-6 weeks before they are planted outdoors. Don’t depend on natural sunlight from a window sill to grow your plants. This light is often inconsistent and will produce spindly plants. Instead grow them under cool-white fluorescent lights. The lights should be on for 14-16 hours per day and kept about 2 inches from the top of the young seedlings. Don’t over-water, and keep the temperature at 70-75 degrees F. during the day and 65 degrees F. at night. Check seed catalogs or packets to determine the best time to start seeds indoors. Some flowers like begonia, sweet peas, geraniums, and impatiens are slow to develop and need to be started 10-12 weeks before the last expected frost. Others that are fast to germinate like sunflowers and zinnias only require 2-5 weeks.

• Vines – Try something new in your landscape this year, consider growing interesting annual vines like cardinal climber, hyacinth bean, morning glory, etc. to cover fences, gazebos and trellises. Check seed catalogs for improved varieties and prepare to start these climbers indoors 6-8 weeks before the last frost, which is around May 10 in Central Maryland.

• Pansies are now widely available at nurseries and garden centers and can be planted for an early display of color in garden beds. Pansies are great for cold wet springs; they can easily tolerate freezing and snowfall even when in full bloom. Pansies are a cool weather plant that decline quickly when it starts getting hot. They are then dug out and discarded in the compost pile after blooming.

• Cut down perennials and over-wintering ornamental grasses to within 2 inches of the ground and remove plant debris from flower beds. This makes for a much neater appearance when the new growth emerges later this spring. It also has the benefit of reducing overwintering diseases. Divide perennials, and top-dress beds with 1 inch of compost. Pull weeds and apply a two-inch layer of mulch to prevent more weed seeds from germinating.
  

• Remember not to set out tender annuals (impatiens, marigolds, petunias, salvia, etc) until after the last frost date. This date varies across the state from late April on the Lower Eastern Shore to Late May in Western Maryland. See our Spring frost/freeze table.
  

• Spring bulbs are emerging and some are even flowering at this time. Exposed leaves may be burned later by very cold temperatures but the spring flower display will not be adversely affected.
  
  

• If you still have unplanted bulbs from last fall, plant them this month. Inspect them carefully and only plant the best quality. Many may be in bad condition and not worth planting. If they were stored where it was warm, they likely will not flower this year but once getting established should do well next year.

• Groundcovers are arriving in local nursery and garden centers this month. They are a great alternative to grass where grass won’t grow, where you have heavy shade or tree root problems and on steep slopes. Select plants based on the amount of sun they require. Good choices include periwinkle, liriope, epimedium, and sweet woodruff. Groundcovers are also useful as a border around buildings and garden beds. However, do not plant these rapid growers next to woodlands where they may become invasive.
  
  
  • Gently rake out leaves and debris from groundcovers and prune out dead leaves and stems. Fallen tree leaves that pile up and mat around groundcovers can lead to foliar diseases in the spring. Trim back English ivy that is invading walkways, turf and garden beds.

• Aquatic Gardening - Get a head start on your pond chores by cleaning out leaves and debris with a net. This will help reduce problems with algae. Small ponds can be completely pumped out, cleaned and refilled. The sooner you can do this the better because by April many species of amphibians will lay their eggs in the pond and you don’t want to disturb them. If eggs have already been laid be very careful and gentle when cleaning the pond to avoid harming them.

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APRIL

• Early to mid April is the latest time that all types of annuals can be started from seed indoors under cool, white fluorescent lights. Most annuals and vegetables need a five week head start before planting outside. A few flowers like begonia, sweet peas, geraniums, and impatiens should be started 10-12 weeks before the last expected frost. You can also head start seedlings in cold frames outdoors.

• Butterfly weed, California poppies, gaillardia, cleome, bachelor’s buttons, strawflowers, chamomile, alyssum, nigella, and annual phlox can be directly sown into the garden at this time.

• If you haven’t already done so, now is the time to clean out flower beds and divide over grown perennials. Cut down over-wintering ornamental grasses to within 2 inches of the ground. These plants are growing fast and its best to get the old debris out of the way. For best growth and flowering top-dress the beds with 1 inch of compost.

• You can weaken and kill poison ivy (HG34) and other invasive plants, like Japanese honeysuckle, by cutting them to the ground now and throughout the growing season. Do not handle the hairy poison ivy vines wrapped around trees. Sever them at ground level and paint the cut end with Brush-B-Gone or a glyphosate product.
  

• Spring Bulbs - Most types have fully emerged and are flowering at this time. Remove the spent flowers but leave bulb foliage alone until it dies back naturally. Now is a good time to apply a complete fertilizer (i.e. 10-10-10) to enhance leaf growth. Healthy leaves make for stronger and larger bulbs. Apply either a granular or liquid form. Follow label directions.
  
  
  • Squirrels, rabbits and deer are notorious for eating tulip buds and can be discouraged with commercially available repellents. Wildlife will not eat narcissus as they are toxic to them.

• Groundcovers - April is an ideal time to plant herbaceous groundcovers. Consider planting groundcovers where grass won’t grow, where you have heavy shade or tree root problems and on steep slopes where it’s not safe to mow grass. Select plants based on the amount of sun they require. Good choices for partial to full shade include periwinkle, liriope, epimedium, sweet woodruff and pachysandra (Japanese and native). Groundcovers are also useful as a border around buildings, garden beds and groupings of trees. However, do not plant rapidly spreading types (i.e. English ivy, pachysandra) near property lines or woodlands where they can become invasive.

• Vines - For a little extra interest and dimension to your landscape, plant annual vines like cardinal climber, hyacinth bean, morning glory, etc. to cover fences, gazebos and trellises. All are easy to grow, have very colorful flowers and are easy to clean up in the fall because they are killed by the cold. You can head start them indoors about three weeks before the last frost date for your area or sow their seeds directly in the soil after the frost date. (See frost date chart.)
  
  
• The clematis is a very beautiful perennial flowering vine. There are several varieties to select. Clematis frequently has a lot of winter killed stems. Prune the dead wood out now before the new growth has fully emerged.

Water Gardening

• As your pond warms up, algae will start to grow rapidly. Excessive algae growth is a very common problem in many backyard ponds. To reduce algae problems in your pond it’s important to clean out dead leaves and other organic debris. Do this as soon as possible as not to disturb the breeding and egg laying of toads, frogs and salamanders. Some amphibians such as wood frogs have already started laying eggs. Be careful not to damage their eggs masses. If breeding has already started, very carefully remove leaves and debris with a large hole net (i.e. fishing net). But do not disturb the eggs. If you can’t do this, wait until breeding is finished and the tadpoles have all hatched in a couple of weeks before removing debris.

• A filter can help reduce algae growth by absorbing the excess nutrients that feed algae. A pond filtration system is composed of a mechanical part that catches larger pieces of debris (foam filter pads) and a biological portion (i.e. the bacteria which grows on the gravel, lava rock, plastic Bio-structures) that removes excessive nutrients. Another effective way to reduce algae problems is by covering 40%-60% of the pond surface with water lily pads. The water lily pads (leaves) shade the water thus reducing the amount of sunlight penetrating the water. Less light means less algae. Dyes that darken the water can also be used to mange excessive algae in ponds that do not have enough water lilies.

• April is a good time to divide water lilies and other aquatic plants that have become overcrowded. Lift the plants from their containers and using a large knife or a sharp spade cut the rhizomes into two or more pieces. Replant and add fertilizer tablets.
  Fountains, statuary and filters can be placed back into ponds at this time. See HG17 for details on aquatic plants.

MAY

• The frost-free date for Central Maryland is May 10 – think Mother’s Day! Plant all warm season annual plants at this time. Purchase stocky, transplants with healthy, white root systems. Remove any flower buds or opened flowers when you get them home to hasten root establishment. This will help direct the plants’ energies to root development and will result in more productive plants. Gently breakup the roots of root-bound transplants. Summer annual bulbs like gladiolus, tuberous begonias, cannas, caladium and dahlias can be planted now. Perennial plants can be safely divided and moved at this time.

• Soluble starter fertilizers can be applied to the foliage or root-zone of spring flowers to get them off to a fast start. These fertilizers have a high percentage of phosphorous relative to nitrogen and potassium. The middle number on the fertilizer label will be highest. Seaweed extracts, fish emulsion, manure and compost teas can be used as well. Sweep or wash granular fertilizers off of plant foliage.

• Fertilize spring flowering bulbs with a balanced fertilizer like 10-6-4 or 10-10-10. Leave the foliage of spring flowering bulbs alone until the top growth dies back. The green foliage is producing sugars to maintain good bulb health.

• Consider planting a groundcover this spring in areas of your yard where the turf is consistently weak. Groundcovers are especially useful on slopes, in shaded areas under trees, and as a border around buildings and garden beds. Before planting a groundcover, work in organic matter and add lime and fertilizer according to soil test recommendations. Groundcovers for sunny areas include creeping thyme, phlox, artemesia, creeping dianthus, oregano, plumbago, and lambs ear. Some good shady area groundcovers include vinca minor, astilbe, epimedium, coral bells, wild ginger, hosta, mazus reptans, and sweet woodruff. Check with local nurseries for other plant ideas and specific cultivars. Groundcovers are also useful as a border around buildings and garden beds. However, do not plant these rapid growers near property lines or woodlands.

• This is a good time to lay down organic mulches, like pine bark, to moderate soil temperature and suppress weed growth in flower beds.

• Consider growing annual vines like cardinal climber, hyacinth bean, morning glory, etc. to cover fences, gazebos and trellises. Hops are a fast growing perennial that can be planted now and allowed to climb on a fence or trellis. Or try planting a hardy climbing rose in a sunny spot against a building or fence.

Pests

• You may notice streaking in iris foliage caused by young iris borers. (photo) The larvae then tunnel down and feed on the rhizome. The leaves and flower stalks may wilt. The best control is prevention. Do not mulch your irises, plant rhizomes high in the planting bed and select full sun sites. If you suspect borers, dig up the rhizomes after bloom, cut off rotted and infested portions and re-plant.

• You’ll begin to see slugs on all types of flowering plants. They chew small holes in leaves and can also shred leaf tissue with their rasping mouthparts. (photo) Slime trails are a definitive sign of slug activity. (photo) They breed in protected, damp areas under boards, in ground covers and under thick mulches. They can be controlled with a directed spray of vinegar and water, with traps and baits and, of course, handpicking. They can be trapped with shallow pans of water and bread yeast or beer. You can also set out boards or half grapefruit rinds to attract them. The slugs will congregate under the boards and grapefruit rind and they can be picked and destroyed. Diatomaceous earth, sharp sand or ground crab and oyster shell can be applied around plants as physical barriers. Chemical baits are also available. Be sure to carefully read the label.

• Four-lined plant bugs are feeding on a wide range of woody and herbaceous plants, especially mint. The adults are yellowish-green with 4 black stripes. The nymphs are bright red. The bugs leave rows of small, round dark spots on leaves. Plants typically grow out of the feeding damage. (Read more...)

• The fungal disease, Phomopsis, can show up on vinca which can cause dieback and can be controlled by thinning out beds. (Read more...)

• Tear-a-thumb, also known as mile-a-minute vine, germinates in early spring and can be seen growing now. The triangular shaped leaves have stems with recurved spines. This invasive, viney weed can quickly take over a garden bed. Control by hand-pulling or an application of a glyphosate herbicide. (HG 88)

Aquatic Gardens

• Algae growth is rapid in the spring when the pond is fully exposed to the sun before water plants begin to make vigorous growth. Starting up your filtration system will help control algae growth. The biological component of the filter will reduce algae growth by absorbing the excess nutrients that feed algae. The biological component of a filter is the last stage in water cleansing. It may have gravel, lava rock or special plastic structures that the beneficial bacteria grow on. The bacteria will absorb nutrients, thus reducing the food for algae. Once water plants begin to cover the water surface the algae problem will subside. Be sure to plant a sufficient number of plants to cover about 60% of the pond surface.

• Now is a good time to divide and repot hardy water lilies and other crowded aquatic plants. Fertilize your aquatic plants with products recommended for aquatic plants. Wait until June to plant tropical water lilies.

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JUNE

• Attract beneficial insects to your landscape by planting a wide variety of flowering annuals and perennials that will bloom over the entire growing season. Good choices are plants in the following families: daisy (marigolds, daises, asters, mums), carrot (dill, fennel, anise, yarrow, parsley) and mint (all mints and thymes).

• Pinch out the flower buds of asters, mums, goldenrod and other fall bloomers to keep plants bushy and prevent early flowering.

• Many garden weeds, like dock and sheep sorrel (photo), have seed heads that are beginning to ripen. Pulling weeds out of your garden beds at this time will help minimize weed problems. Tear-thumb, also known as mile-a-minute vine (video), germinates in early spring and can be seen growing now. The triangular shaped leaves have stems with curved spines. This invasive weed can quickly take over a garden bed. Control by hand-pulling or with an application of a glyphosate herbicide. Weaken and kill invasive plants, like Japanese honeysuckle, by cutting them to the ground now and throughout the growing season. (HG 88)

• Cut Iris flower stalks down to the crown when they are finished blooming. Leave the foliage alone. If your iris are over-crowded, June, after flowering, is the recommended time to lift and divide them.

• Let spring bulb foliage die back naturally. Don’t fold over or braid foliage. At this time the bulb absorbs nutrients it requires for growth the following year.

• Flower beds should be mulched now that the plants are growing vigorously. Shredded bark mulch or chopped leaves make good mulches. The depth should be no more than 2-3 inches to be effective. Avoid placing mulch against the plant stems. This can cause rot of the lower stem to occur.
  

• Groundcovers - Consider planting a groundcover this spring in areas of your yard where the turf is consistently weak. Groundcovers are especially useful on slopes, in shaded areas under trees, and as a border around buildings and garden beds. Before planting a groundcover, work in organic matter and add lime and fertilizer according to soil test recommendations. Groundcovers for sunny areas include creeping thyme, creeping phlox, creeping dianthus, oregano, plumbago, and lambs ear. Some good shady area groundcovers include vinca , astilbe, epimedium, wild ginger, hosta, and sweet woodruff. Check with local nurseries for other plant ideas and specific cultivars. Groundcovers are also useful as a border around buildings and garden beds. However, do not plant these rapid growers near property lines or woodlands where they may invade into these areas.

• Vines – Annual vines add a special colorful touch to any landscape. Some great annual vines to consider include scarlet runner and hyacinth beans, cardinal flower, moonflower, mandevilla, thunbergia (black-eyed Susan vine), nasturtiums and morning glories. Hops make an interesting, fast-growing perennial vine and produce fragrant cones used in beer making. They can be planted now and allowed to climb on a fence or trellis.

Insects

• Aphid numbers are high now on a wide variety of plants. Aphids are small, soft-bodied insects that come in many different colors and suck the plant sap from a wide variety of plant leaves. They may cause leaves to pucker, twist and curl downwards. It is usually not necessary to spray insecticides or release beneficials to control aphids. Populations of ladybird beetles, syrphid flies, green lacewings and wasp parasites build up quickly to keep aphids in check. You'll see these predators and parasites at work if you observe the aphid colonies closely.

• Planting a wide variety of flowering plants that bloom throughout spring and summer will help attract and keep beneficial insects in your landscape. If necessary, an application of insecticidal soap or ultra fine horticultural oil will kill these soft-bodied pests. Aphids excrete a sticky product called honeydew, when they feed. This leads to the growth of a black fungus on leaves, known as sooty mold. See HG83 and HG94

• The damage from four-lined plant bug feeding can be seen on a wide variety of plants. Insects are yellow with four black stripes down the back and produce small, circular dark spots, usually on new growth. No controls are necessary. Plants will outgrow moderate feeding damage.

• Iris borer larvae tunnel down and feed on the rhizomes. The leaves and flower stalks may wilt. The best control is prevention. To prevent borer attack do not mulch your irises, plant rhizomes high in the planting bed and select full sun sites. If you suspect borers, dig up the rhizomes after bloom, cut off rotted and infested portions and re-plant.

• Thrips feed on flower buds and opened flowers causing them to turn brown. They cause leaf undersides to appear dirty and silvery. Monitor for them by tapping affected foliage or buds over a piece of white paper and look for small quick moving specks. They are slender, minute and appear yellow-brown in color and transparent. Thrips are especially bad on gladiolus and will prevent flowers from opening.

• Slugs are found on all types of flowering plants. Their feeding damage will range from just a few holes to the entire plant stripped of its foliage in a few nights. Slime trails are a definitive sign of slug activity. They breed in protected, damp areas under boards, in ground covers and under thick mulches. They can be trapped with shallow pans of water and bread yeast or beer. You can also set out boards or grapefruit rinds to attract them. Each morning lift these hiding places up and kill the slugs. Diatomaceous earth, sharp sand or ground crab and oyster shell can also be applied around plants as physical barriers. A new product containing iron phosphate is available that is supposed to slowly poison slugs upon ingestion. Iron phosphate is actually a plant ntutrient and is harmless to animals, (except for the slugs). Chemical slug baits are also available. Follow instructions on the label.

Diseases

• You may notice wilt or dieback of vinca or periwinkle, which is caused by a fungus called phomopsis blight that girdles the stem. Clean out your vinca beds to improve air circulation and prune out infected plants. No chemical controls are available.

• Brown, bulls-eye lesions on pachysandra are an indication of the fungal disease volutella. Thin out plants to improve circulation and this disease usually subsides.

• This month you may also notice ivy leaf blight on your English ivy vines this disease can be caused by either a fungus or bacteria. This will weaken your planting and is most severe in thick, overgrown beds where dead leaves have accumulated. Rake out and thin out infected ivy beds. A fixed, basic copper spray can also be applied.

Water Gardens-

• As the weather continues to warm up, both planktonic (cause of green water) and filamentous algae growth will continue to increase. Algae growth is rapid in the spring when the pond is fully exposed to the sun. Later this month after the water lilies’ foliage has covered the surface by 60% the algae problem will subside. The addition of the tropical plants, water lettuce and water hyacinth will help keep your pond water clean and reduce both planktonic and filamentous algae. Mats of filamentous algae can be pulled out by hand. Using a filtration system will also help control algae growth, the biological component of the filter can also help reduce algae growth by absorbing the excess nutrients that feed algae. As a last resort, you can use an algaecide. If you have fish in the pond, be careful that the algae is not killed too quickly. The sudden decomposition of the dead algae can asphyxiate the fish. Aerating the pond with a fountain or waterfall can help prevent this from happening.

• Now is still a good time to divide and repot hardy water lilies and other crowded aquatic plants. Fertilize your aquatic plants with products recommended for aquatic plants. Plant and fertilize tropical lilies in your pond now. It’s important to set plants at the correct depth. Most varieties require 5-6 hours of sunlight per day.
  

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JULY

• Many perennials, like yarrow and salvia, can be cut back now to encourage re-blooming later this summer. Deadhead the spent blooms of annuals like zinnias and marigolds to encourage more vigorous continuous bloom. Cutting sedums back about half way will prevent them from falling over when in full bloom later this summer.

• Chrysanthemums should be cut back about half way at this time to encourage fall blooming. If not trimmed they will bloom later this month and not in the fall.

• Pinch out the flower buds of asters, mums, goldenrod and other fall bloomers to keep plants bushy and prevent early flowering.

• Although this is not the best time to divide and transplant perennials, it can be done if necessary. Divide and re-plant quickly in the early evening, keeping the root system moist at all times. Water the new divisions daily until they are established.

• A number of different pests are feeding on flower petals including slugs, earwigs, and various species of scarab beetles. (HG94)

• Japanese beetles, June beetles and chafer beetles may be feeding heavily at this time. They can consume the foliage and flowers of a wide range of landscape plants. Brush the adults off the foliage and into a bucket of soapy water. You can also use a labeled repellent or insecticide to control these pests. The use of Japanese beetle traps near your plants is not recommended. Use them only if kept very far away from the plants you are trying to protect. This is important because studies show that traps may often attract more beetles to your landscape resulting in increased damage.

• Very large green beetles that resemble giant Japanese beetles are actively flying about at this time. These are green June beetles; their grub stage feeds on organic matter in the soil, the adults do not feed on many ornamental plants but can be damaging to fruit.

• Southern blight, a soil-borne fungal disease, attacks a wide range of herbaceous perennials. Plants that are especially susceptible are echinacea, thyme, coneflower, coreopsis and black-eyed Susan. The disease is encouraged by hot, humid weather and usually starts appearing in mid to late July. Lower stems turn brown or black and plants will wilt and eventually dry up and die. You may also notice a white fungal mat growing over the infected stems. Tan colored fungal fruiting bodies, the size of a small seed, may be observed on affected stems. In some cases only the plant tops are killed. You can cut back the affected parts and expect re-growth. In other cases the crowns are killed and plants need to be removed. No chemical controls are available. Keep mulch away from plant stems and water in the morning to minimize problems with Southern blight.

• A number of leaf spot diseases are active now. Affected leaves can be removed and disposed. Powdery mildew may be seen now on the foliage of many perennials like roses, phlox and monarda. This fungal disease appears as a grayish, powdery coating on upper leaf surfaces and is favored by low rainfall and high humidity. Funginex, a commonly used rose fungicide, will control black spot and powdery mildew. Daylily leaf streak causes lesions that run along the midrib causing browning down to the base of daylily leaves. Remove damaged leaves. Web blight, another disease, attacks low growing perennials like woodruff. Foliage becomes matted and brown. This disease only kills the plant tops, not the crowns. To reduce the incidence of these diseases, remove mulches, work organic matter into the soil and space plants out to improve air circulation.

• Iris leaves that are wilted and chewed are probably suffering from iris borer. The affected rhizomes are mushy and have a foul odor. Iris rhizomes can be dug, cleaned of affected parts and replanted now. Re-plant in full sun and water regularly. Using a mulch around iris tends to attract iris borers. They are best left unmulched.

• You may also notice leaf blight on your ivy vines. This fungus will weaken your planting and is most severe in thick, overgrown beds where dead leaves have accumulated. Rake out and thin out infected ivy beds. A fixed, basic copper spray can also be applied. Clematis requires a soil with neutral to slightly basic (sweet) soil. Test and amend your soil with lime, if necessary, before planting clematis. For best results, mulch the root system to keep it cool during the summer heat. Keep clematis well watered during hot dry spells.

• You may notice wilt or dieback of vinca or periwinkle, which is caused by a fungus called phomopsis blight that girdles the stem. Thin out thick patches of periwinkle and pachysandra. Clean out your vinca beds to improve air circulation and prune out infected plants.
  

• Brown, bulls-eye lesions on pachysandra are an indication of the fungal disease volutella. Thin out plants to improve circulation, and this disease will be managed.

• Inspect wintercreeper and Japanese euonymus foliage for scale problems and apply a summer rate of horticultural oil where these insects are a problem.

• Consider planting groundcovers this spring where grass won’t grow, where you have heavy shade or tree root problems and on steep slopes. Select plants based on the amount of sun they require. Groundcovers for sunny areas include creeping thyme, creeping phlox, creeping dianthus, oregano, plumbago, and lambs ear. Some good shady area groundcovers include vinca, astilbe, epimedium, wild ginger, hosta, and sweet woodruff. Check with local nurseries for other plant ideas and specific cultivars. Groundcovers are also useful as a border around buildings and garden beds. However, do not plant rapid growers near property lines or woodlands where they might invade the woodlands.

• Algae growth will continue until pond plants cover 60% of the pond surface. Using a filtration system will help control algae growth by removing dissolved nutrients. Usually, once water plants begin to cover the water surface the algae problem will subside. Another helpful technique is to place small bales of barley straw in the pond. Now is still a good time to divide and repot hardy water lilies and other crowded aquatic plants. Most aquatic plants, except for the lotus, can be successfully divided even while in active growth. Water lotus is much more sensitive and will be harmed if dug and divided when in full growth. Fertilize your aquatic plants with products recommended for aquatic plants. Plant and fertilize tropical lilies in your pond now. Most varieties of water lilies require at least 6 hours of sunlight per day to bloom properly.

• Gambusia is a good fish to introduce to your pond for controlling mosquitoes. Goldfish, golden orf, rosie minnows and koi can also be added to the pond. The addition of B.t.i. found in ‘mosquito dunks’, is also very good for the biological control of mosquitoes. Very hot weather raises the water temperature and this causes a decrease in the dissolved oxygen in the water. This will stress and kill larger fish as they cannot breathe. Aerate your pond with a pump, filter or fountain. Adding fresh, non-chlorinated water can also help.

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AUGUST

• Annuals and perennials, like yarrow and salvia, may have grown spindly and are not flowering well. Cut them back to encourage re-bloom. Deadhead the spent blooms of annuals like zinnias and marigolds. This will encourage them to continue blooming more vigorously.

• Plant hardy mums for fall color this month so they will become well established prior to the winter.

• Late August through September is usually a good time to transplant, divide and plant perennials such as daylily, liriope, and Echinacea. Be sure to keep them well watered during dry periods. If the current hot, dry conditions persist wait to divide your perennials.

• Poison ivy foliage can be effectively controlled with a labeled herbicide applied to the foliage later this month. You will have to make multiple applications to significantly weaken and kill the plants. If you cannot reach the foliage to spray, cut the vine down to the ground. Treat the cut surface still attached to the roots, with glyphosate or triclopyr. Do not handle the hairy poison ivy vines with bare hands even after they have died back.

• This is a good time to apply glyphosate to control bamboo shoots and other hard to control weeds because this is when the plants are transferring nutrients to the roots.

• Sawfly larvae (HG94) have been observed feeding on hibiscus. Their damage causes extensive skeletonization of leaves. The larvae are small, green and resemble caterpillars. Light infestations may be controlled by manually removing and destroying sawfly larvae.

• Irises with leaves that are flopping over may be infested with iris borer, the larva of a clear wing moth. The eggs are laid on the foliage in the spring and the larvae move down to the crown and bore into the rhizome. A smelly bacterial rot usually follows infestation by the borer. This is a very destructive pest. Dig up infected plants and cut out the larvae and damaged tissue and discard infected plants – do not compost infected material. Re-plant the healthy rhizomes.

• In hot, dry weather, spider mite populations can be high on many landscape plants. Damage occurs on a wide variety of flowering plants. Spider mites are pinpoint size sucking pests that can be observed on leaf undersides with the unaided eye. Keep plants hosed down during hot dry weather. Spraying insecticidal soap or horticultural oil on mite damaged plants during hot weather can cause serious leaf burn. If you notice spider mite damage on different types of plants in your yard you might consider purchasing and releasing beneficial mites, which will hunt down and consume the pest mites. They are a good value and environmentally safe.

• Even in hot and dry weather, slugs continue to be active through the summer. The three types of slugs found in this area are the spotted garden slug (3-5inches), the tawny garden slug (2-3 inches) and the gray garden slug (2-3 inches). They cause damage (large holes in leaves) to a wide variety of annuals and perennials. Favorite plants include hosta, salvia and marigold. Set out shallow saucers of beer or yeast mixed in water to attract and drown the slugs. Safe and effective baits containing iron phosphate are widely available. Sprinkling used coffee grounds around plants can also be very helpful in repelling slugs. Read label directions on all products for safe and effective control of slugs. Note: some baits can be harmful to pets and other small animals.

• Southern blight is a significant disease of annuals and perennials encouraged by hot, humid weather. It is a soil-borne fungal disease that attacks a wide range of perennials including thyme, coneflower, coreopsis and black-eyed susan. Affected lower stems turn brown or black, foliage wilts and plants will eventually dry up and die. Tan colored fungal fruiting bodies, the size of a small seed may be observed on affected stems. You may also notice a white fungal mat growing over the infected stems. In some cases, plants can be cut back to the ground and plants will re-grow. However, the disease may kill crown and roots and plants will need to be removed. Keep mulch away from plant stems and water in the morning to minimize problems with southern blight. Working organic matter into the soil may help lessen the problem. No chemical controls are available. Read more...

• Rhizoctonia web blight is a problem on sweet woodruff and other perennials, which produces similar symptoms to southern blight. Foliage becomes matted and brown. Rhizoctonia usually does not kill roots or crowns. To reduce the incidence of disease, remove mulches, work organic matter into the soil and space plants out to improve air circulation. Read more...

• Powdery mildew may be seen now on many perennials, like roses, phlox, peonies, and Monarda. This fungal disease favors high humidity and unlike other fungi does not require wet weather to thrive.. Powdery mildew may be observed on plant foliage as a grayish, powdery coating on upper leaf surfaces. When possible select resistant cultivars. Read more...

• Groundcovers - If turf grasses have failed due to poor location (i.e. too shady for turf), consider planting appropriate groundcovers this fall. Soil should be loosened and organic matter incorporated prior to planting. Select plants based on the amount of sun they require. Good choices include striped or spotted wintergreen, trailing arbutus, moss phlox, Epimedium, sweet woodruff, partridge berry and ferns. Groundcovers are also useful as a border around buildings and garden beds. However, do not plant rapid growers near property lines or woodlands where they can become invasive.

• Periwinkle/Vinca are prone to another fungal disease called Phomopsis blight that causes plants to wilt and turn brown. Prune out infected plants. No chemical controls are available.

• You may have hostas that are yellowing and becoming scorched. In many cases this was caused by a combination of hot, dry conditions and diseases like Alternaria and Anthracnose (Colletotrichum). Remove badly affected leaves to slow down the progression of this leaf disease.

• Water Gardens – Water lilies are growing rapidly and should be fed with fertilizer tablets regularly according to label instructions. Periodically remove the older, yellow leaves and spent flower heads of tropical lilies.

• The water lily leafminer is a common pest that produces serpentine mines in leaves. Simply remove and discard affected leaves. The china mark moth larva is another pest of lilies. The larvae live in small packets of leaf tissue and float on the pond eating holes in the edge of lily pads. Pick off and dispose of the affected foliage.

• Floating plants such as water lettuce and water hyacinth are tropical plants that can help keep your pond water clean. Their roots act as filters and the plants shade the water thus reducing algal growth.

• Tropical lilies are at peak bloom and will continue flowering through frost. Keep them fertilized to encourage strong blooming. Trim off and remove ragged and dead plant parts. Weak or dying plant parts should be removed to help keep the water clean. Water lily aphid feeding has been observed. Remove heavily infested leaves or direct a strong water spray at the aphids.

• Now is a good time to clean out excessive plant growth in your pond and remove dead or diseased leaves. If you have a circulator like a filter or a fountain, keep it running during hot weather to increase the amount of oxygen available for your fish. The heat will evaporate water and ponds will need topping off. If using public water do not add large amounts of water at one time. The chlorine added to public water systems may kill fish. Chlorine is not an issue if you are using well water.

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SEPTEMBER

• Watch for white rust on mums. The symptoms initially are yellow spots before they turn to white pustules. All infected plants should be destroyed.

• Plant hardy mums now so they will become well established prior to cool weather. Pansies and ornamental cabbage and kale can also be planted. Most perennials left in the same place for more than three years are likely to be overcrowded, with dead unsightly centers. The center of the clump will grow poorly, if at all, and flowering will be sparse. September is a good time to transplant, divide and plant perennials. Be sure to keep them well watered during dry periods.

• Irises with leaves that are flopping over may be infested with iris borer. The borer is the larva of a clear wing moth. The eggs are laid on the foliage in the spring and the larvae move down to the crown and bore into the rhizome. Dig up infected plants and cut out the larvae and damaged tissue. Re-plant the healthy rhizomes. Do this now so that the iris plants will have time to become established before winter.

• Consider planting a groundcover in areas of your yard where the turf is consistently weak. Groundcovers are especially useful on slopes, in shaded areas and as a border around buildings and garden beds. Now is a good time to plant groundcovers, be sure to water them daily until well established.

• Now is the time to plant daffodil bulbs in a sunny spot in well-drained soil. Tulip bulbs should be planted from mid-October through November. Mix a balanced fertilizer into beds before planting bulbs this fall. Follow package instructions for planting depth and spacing. If you’ve had trouble with deer eating your tulips, plant daffodils (narcissus) instead. They are not eaten by deer.

• Most perennials left in the same place for more than three years are likely to be overcrowded, with dead unsightly centers. The center of the clump will grow poorly, if at all, and flowering will be sparse. September is a good time to transplant, divide and plant perennials. Be sure to keep them well watered during dry periods.

• A number of well-adapted vines like cardinal climber, trumpet creeper, and fall-blooming clematis are blooming strongly now. These can all be planted at this time. Consult local nurseries and garden catalogs for appropriate varieties. Another attractive vine is hops; the cones can be harvested and used in beer making or herbal sachets. It is best not to plant clinging-type vines on or near wooden structures.

Water Gardens

• Tropical lilies will continue to bloom until frost. Periodically remove the older yellow leaves and spent flower heads of tropical lilies. The water lily leafminer is a common pest that produces serpentine mines in leaves. Simply remove and discard affected leaves. The china mark moth larva is another pest of lilies. The larvae live in small packets of leaf tissue and float on the pond eating holes in the edge of lily pads. Pick off and dispose of the affected foliage. Avoid spraying pesticides around your pond. Aquatic plants and animals are very sensitive to chemical sprays.

• Consider laying a wire screen over your pond during the fall months to keep leaves out. Cut down and remove all plant parts that succumb to frost and freezing weather. Tropical lilies should be allowed to die outside; they are very difficult to overwinter inside. As the weather gets colder, stop feeding your fish. They cannot metabolize food easily during cold weather. Stop fertilizing plants at this time. Continue to remove dead plant parts.

• You may have noticed mile-a-minute vine , also known as tearthumb, (Polyganum perfoliatum) creeping around your landscape this summer. This is a very invasive, imported annual weed that has spread throughout Central Maryland. The leaves are triangular and the stems and leaves are covered with small recurved thorns. It’s a poorly rooted annual that can grow 20-25 ft. in one season. It will cover and smother shrubs, flowers and other landscape plants. It produces attractive small blue berries that can be seen now. It’s important to control this weed before the seeds develop. If the vine is growing over desirable plants, hand pulling is your only option.

• Powdery mildew may be observed on many flowers in the fall as a white, powdery coating on upper leaf surfaces. No chemical controls are necessary. However, you may want to consider spraying horticultural oil at the summer rate in July-August next year on plants that have had a problem with powdery mildew this year.

• The three types of slugs found in this area are the spotted garden slug (3-5inches), the tawny garden slug (2-3 inches) and the gray garden slug (2-3 inches). They cause damage (large holes in leaves) to a wide variety of annuals and perennials. Favorite plants include hosta, salvia and marigold. Set out shallow saucers of beer or yeast mixed in water to attract and drown the slugs. Commercial baits can be used, but follow safety precautions on label to protect children and pets. Many of the new products contain safer chemicals such as iron phosphate or soap. See fact sheet HG 92 on slugs for more information.

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OCTOBER

• Mums that are planted this late should be treated as an annual. They will not become established over the winter. Fall-planted asters, however, will become established. Ornamental kale and cabbage produce a nice show of foliage but usually decline by February. Pansies are a good choice for fall and winter color in the garden. This is a good time to save the seed from annual flowering plants like cleome, zinnias, cosmos, celosia and butterfly weed.

• Powdery mildew may be observed on plant foliage as a white, powdery coating on upper leaf surfaces. Removed fallen leaves and debris from the garden; no chemical controls are necessary.

• Now is the recommended time to divide and replant overcrowded perennials. Most are easily divided but a few such as Baby’s Breath, Gas Plant, Butterfly Weed, and Lenten Rose do not tolerate being divided. (HG 99)

• Leave the flower heads on sunflowers, coneflowers, coreopsis and black-eyed Susan to provide winter food for birds.

• Geraniums can be over-wintered in several ways. Entire plants can be brought inside and grown in a sunny window, or cuttings can be taken from existing plants. You can also take cuttings from other annuals like begonias, salvias, and coleus.

• Daffodil bulbs, tulips, alliums and other bulbs can be planted now. For best results plant them in a sunny spot, in well-drained soil. Daffodil bulbs are the first to be planted and tulip bulbs should be planted from mid-October through November. When planted sooner they will often grow and sprout to the surface this fall. Mix a balanced fertilizer into the planting soil and set the bulbs three times the depth of the bulb width. Mulch the area and be prepared to cover the bulbs with some type of wire mesh material if voles and squirrels have been a problem in the past.

• A tip for gardeners with deer problems, they love to eat tulips but usually will not eat daffodils.

• You may have noticed mile-a-minute vine, also known as tear-a-thumb, (Polyganum perfoliatum) creeping around your landscape this summer. This is a very invasive, imported weed that is spreading throughout Central Maryland. The leaves are triangular and the stems and leaves are covered with recurved thorns. This poorly rooted annual can grow 20-25 ft. in one season. It produces attractive blue berries that can be seen now. It’s important to control this weed before the seeds develop. Glyphosate herbicide can be used to control it. Hand pulling before berry production is also very effective. (See article in the Fall 2011 issue of the Home and Garden News)

• Early October is a good time to apply glyphosate to bamboo, multiflora rose and other difficult to kill plants, because this is when the plants are transferring nutrients to the roots for winter dormancy. The success rate in controlling these weeds is very good when applied in the fall prior to dormancy.

• Other invasive plants include climbing euonymus, five-leaf akebia, kudzu, mile-a-minute, oriental bittersweet, porcelain berry and wisteria. Cut down invasive weeds that are producing seeds. For more information on invasives, see publication HG 88 or visit www.mdinvasivesp.org.

• This is a good time to renovate your groundcovers if they have performed poorly and look weak and diseased. Mow them close to the ground and rake out and dispose of all plant debris. Wait until spring to fertilize. Fall is also a good time to plant groundcovers on bare and eroded areas. (HG 89)

• Consider planting a groundcover in areas of your yard where the turf is consistently weak. Groundcovers are especially useful on slopes, in shaded areas and as a border around buildings and garden beds. Soil should be loosened and organic matter incorporated prior to planting. Select plants based on the amount of sun they require. Good choices include striped or spotted wintergreen, trailing arbutus, moss phlox, epimedium, sweet woodruff, partridge berry and ferns. However, do not plant rapid growers such as pachysandra or English ivy near property lines, trees or woodlands. They may become a very invasive problem to neighbors or the woods.

• There are three types of slugs found in this area: the spotted garden slug (3-5inches), the tawny garden slug (2-3 inches) and the gray garden slug (2-3 inches). They cause damage (large holes in leaves) to a wide variety of annuals and perennials. Favorite plants include hosta, salvia and marigold. Set out shallow saucers of beer or yeast mixed in water to attract and drown the slugs. Commercial baits can be used, but follow safety precautions on label to protect children, pets and wildlife. (HG 92)

Diseases

• Brown, bulls-eye lesions on pachysandra are an indication of the fungal disease volutella. Thin out plants to improve circulation and reduce this disease for next year. (More info.)

• Periwinkle and vinca are prone to another fungal disease called phomopsis blight that causes plants to wilt and turn brown. Prune out infected plants. No chemical controls are available. (More info.)

• Web blight attacks low growing perennials like sweet woodruff. Foliage becomes matted and brown. This disease only kills the plant tops, not the roots. To reduce the incidence of these diseases, remove mulches, work organic matter into the soil and space plants out to improve air circulation.

• Large black or dark brown blotches seen on the leaves of peonies this late in the season are caused by two common fungal diseases of peony - Cladosporium and Botrytis blight. Botytis blight is also very destructive to next year’s flower buds. Sanitation is a first important step in managing these fungal diseases. Cut off and remove all plant debris each fall.

Water Gardens

• Tropical water lilies will begin to die in late October. Don’t try to keep them over the winter; they are very difficult to successfully overwinter inside. Cut down and remove all plant parts that succumb to frost and freezing weather. Cover your pond with a small mesh wire screen, like chicken wire or bird netting, to keep fallen leaves out during the fall and winter. Consider buying a stock tank heater for small ponds. This will prevent the pond from freezing over completely during the winter. As the weather gets colder, stop feeding your fish. They cannot metabolize food easily during cold weather.

• You can continue to run filtration and pumps throughout the winter. The moving water will not freeze and provides aeration for the fish. It also reduces freeze- over of the surface. Fountains and statues should be removed as ice will damage them.

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NOVEMBER

• Pansies are a good choice for fall and winter color in the garden. If you want to plant pansies you need to do it very soon to assure that their roots get established for winter. Perennials can still be divided and replanted at this time.

• Don’t begin mulching your perennials until after the first hard freeze- around mid-November. The mulch should be 2-3 inches deep and surround the plant crowns. Waiting to mulch will help the ground to cool and remain cold during winter. The freezing and thawing of the soil in winter can cause many perennials to heave; mulching helps moderate temperature fluctuations thus, reducing this problem.

• Cut back and compost other annuals and perennials after hard frost kills the top foliage. Do not compost foliage from plants that suffered from disease problems this season. Fall garden clean-up may result in a healthier garden next season by reducing disease spores and insect eggs, which overwinter in plant material.

• It’s time to dig summer bulbous and tuberous plants, such as cannas, dahlia, gladiolus, caladium or tuberous begonia, and store them indoors for the winter. After digging, remove loose soil and cormels (the small newly-formed corms found on gladiolus and other corms, Fig. 1), cut the foliage back to just above the bulb and spread them out to cure for one to three weeks. Allow a 4-6” stem to remain above the cannas and dahlia tubers. This will help prevent a rot of the tubers while in storage. Store bulbs in paper or mesh bags, cardboard boxes, or nylon stockings. Cover or layer the bulbs with peat moss, perlite or vermiculite. Store in a cool (40- 50 degrees), dry place and check periodically for shriveling or decay. Store caladiums, dahlias and tuberous begonia in slightly moistened peat moss. Gladiolus requires an 8-week chilling period at 35-41° F.

• Spring flowering bulbs can still be planted, for best results place them in a sunny spot in well-drained soil, amended with compost. Fertilize the planting area with a balanced fertilizer containing nitrogen, phosphorous and potassium. Bulbs can be protected from animal pests by surrounding them with a wire mesh like chicken wire. If deer or other wildlife have ravaged your past bulb plantings, try planting bulbs that are rarely damage by deer, such as Allium, Narcissus, Fritillaria, Hyacinth, and Scilla.

Water Gardens

• Cover your pond with a small mesh screen, such as chicken wire or plastic bird netting, to keep the leaves out during the fall and winter. For maximum freeze protection for your pond fish install a stock tank heater for small ponds to prevent them from freezing over completely during the winter.

• Now is the time to cut down and remove all water plant parts that have succumbed to freezing weather. Tropical lilies should be allowed to die outside; they are very difficult to overwinter inside.

• Stop feeding your fish. They cannot metabolize food easily during cold weather.

• Clean up pond statuary. Remove them from the water to prevent freeze damage. Cover large fountains that cannot be brought inside with plastic to prevent snow and ice damage.

• You can actually safely run a pump and filter through the winter. The constantly moving water will not freeze. The moving water also helps to distribute oxygen through the water for the fish. If you are not going to keep the pump and filter operating, remove them to prevent them from freeze damage.

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• This is a good time to save the seed from annual and biennial flowering plants like cleome, zinnias, cosmos, celosia and butterfly weed. Leave the flower heads on sunflowers, coneflowers, coreopsis and black-eyed Susan to provide winter food for birds. Dahlia tubers, canna rhizomes, and Elephant Ear bulbs should be lifted and stored in sawdust or potting mix in a cool, dry location, like an unheated garage or unheated part of a basement, where temperatures will remain above freezing. Rub the excess soil off the roots and tubers, do not wash the soil off them with water, it can cause a rot problem in storage.

• Plant any leftover bulbs in the garden as long as the soil can be worked. Plant only solid, healthy bulbs. Discard bulbs that are shrunken, mushy or obviously not in good condition. The site for bulbs should be sunny, well-drained and ideally the soil should be well-amended with organic matter. Fertilize the planting area with a balanced fertilizer containing nitrogen, phosphorous and potassium. If fertilizer is used it is not necessary to apply bonemeal. The strong organic odor of bonemeal sometimes attracts wildlife that may dig up the bulbs. Bulbs can be protected from animal pests by placing a wire mesh, like chicken wire, on the soil. The leaves and flower stems will grow through the chicken wire.

• Holiday Plants - If you plan on purchasing and then planting a live Christmas tree, you may want to dig the hole ahead of time when the ground is not frozen. For more tips, read HG46, “Selecting and Caring for a Live Christmas Tree”. If you are purchasing a cut Christmas tree, read HG 45, “Selecting and Caring for a Cut Christmas Tree”. For care of Poinsettias, see our publication HG30.

Water Gardens

• If you did not cover your pond to prevent leaves from falling in, spend some time now to remove those leaves. The decomposing leaves will produce gases that when trapped under the ice will sicken or kill your fish. Cover the pond with screen after its been cleaned. Consider buying a stock tank heater for small ponds to prevent them from freezing solid during the winter.

• Discontinue feeding your fish, although they might still eat some food they cannot properly metabolize food easily during cold weather. This can lead to sickness or death.

• Clean up pond statuary, fountains and other concrete or plastic pond features, remove them from the water and cover these items with plastic to prevent snow and ice damage. You can leave outdoor filters and pumps running throughout the winter; moving water will not freeze. If you don’t leave them running, bring them inside to prevent ice damage.
  

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