March Gardening Tips and Tasks

• Design a native plant garden, or choose a few native plants you could grow in containers on a deck or balcony. Locally-native plants are adapted to Maryland’s climate and soils, and support pollinators, songbirds, and other wildlife.
• Good soil grows healthier plants: improve your soil with no-till or low-till gardening, and use compost as needed to amend poor soil. Keep the ground covered with a mixture of plants, and avoid disturbing the soil as much as possible. Instead of digging, smother weeds or turf to prepare a new garden bed.
• Buy disease-resistant varieties of plants, if options are available. For example, some cultivars of flowering dogwood (Cornus florida), such as ‘Cherokee Brave’ and ‘Jean’s Appalachian Snow’, are resistant to powdery mildew.
• Become a community scientist in your garden. Your observations about the timing of plant budding and flowering, bee foraging preferences, and bird sightings can contribute to scientific research. Learn how you can help.

• March is the beginning of the planting and transplanting season for trees and shrubs. Avoid digging into or walking on wet soil; wait until the soil dries out so it doesn't compact. How do you know when your soil can be worked? A simple test is to form a clump of soil into a ball. Bounce it up and down in your hand a few times -- if it breaks apart easily, it’s probably okay to dig!

• Leaf scorch symptoms ("winterburn") can appear on broadleaved evergreens. Damage tends to be more severe on shallow-rooted plants (azalea, rhododendron, boxwood), as well as holly, cherry laurel, or species at their northern limit for winter hardiness (Southern magnolia, aucuba, camellia). In many cases, damage occurs during the winter months, but symptoms may not appear until spring, as the plant begins to resume growth after emerging from winter dormancy.

• Prune roses around mid-March to manage their shape and size and to cut back old or crowded canes (stems). Roses typically experience some winter cane dieback. To determine whether or not a cane is alive, scrape the stem with a sharp knife and look for green tissue immediately under the bark. If it is brown instead of green, prune off the dead wood.

• If you have ash trees that need to be protected from emerald ash borer, consult a certified arborist for management options.

• Improve soil quality by mixing one inch of compost into vegetable beds as soon as the soil is workable (not frozen and not too wet).
• There is still time to test the soil in your vegetable garden to learn about nutrient levels, acidity (pH), and organic matter content.
• Cut back overwintered perennial herbs like oregano, thyme, and marjoram. (Leave more shrubby herbs, like rosemary and lavender, largely unpruned.) The trimmed plants will look better and have more room for new growth. Pruning can also help reduce insect and disease problems by lessening stem crowding.
• Start seeds indoors for broccoli, cabbage, collard greens, peppers, and lettuce. You can also direct-sow outdoors Chinese cabbage, lettuce, peas, radishes, spinach, and turnips. Refer to the vegetable planting calendar for guidance on when to plant seeds or transplants based on crop type.

• Perennial foxglove beardtongue and wild bergamot have showy flowers that support native pollinators. Look for native plant sales this spring for species to add to your garden.
• Many types of annual flower plants can be started indoors this month. Most seeds are sown 5 to 6 weeks before they are planted outdoors, which is typically after the last frost date. Sunflowers and zinnias can be directly seeded outdoors after the danger of frost has passed.
• Pansies are widely available at nurseries and garden centers, and can be planted this month for an early display of color in garden beds or containers. They are cool-weather plants, declining when it starts getting hot, when they can be replaced with warm-weather annuals.
• Leave last year's spent perennial flower stalks standing in the garden, or cut them down to varying heights between 8 and 24 inches. These old stems provide nesting sites for native bees that pollinate plants.
• Divide perennials and top-dress garden beds with one inch of compost.

• A spring application of fertilizer should not be necessary if the lawn was fertilized in autumn and is growing well.
• March is considered the second-best time of year to seed a cool-season lawn or lay sod. (The best time to plant cool-season grasses is from late August through mid-October.) Seeding should be completed by late April so the turf can establish before dealing with summer heat and drought stress.

Beneficial insects

• Rove beetle adults will begin to emerge from their overwintering shelters (rock piles and fallen logs) and crawl around the ground looking for food. These beneficial beetles are either predators, feeding on other insects, or are decomposers, helping to break-down organic matter. Support these beetles by leaving fallen leaves and logs to provide needed shelter.
• Cellophane bee adults will begin emerging from their overwintering ground nests. These nonaggressive bees are important native pollinators for a wide variety of plants. You will only see adults coming and going from their ground nests for about a month. (They are not defensive of their nests, so are not inclined to sting.) Support these pollinators by tolerating and conserving their ground nests and by planting a diversity of native flowering plants.
• Praying mantis egg cases (ootheca) are present on various plant stems (and potentially other objects). All mantid species in our area are considered beneficial predators; do not target and kill non-native mantid species. Support mantids by leaving their egg cases outdoors so they can naturally emerge in spring. Do not bring them indoors during fall and winter, as the warm temperatures inside your home could cause them to hatch too early and starve.
• Wheel bug egg masses are present on bark, and nymphs (juveniles) will soon hatch. These beneficial predators feed on a wide variety of insect pests. Learn to recognize their hexagonal-shaped egg masses, and black and red-orange nymphs, so you can leave them alone to provide sustainable pest control.
• Eastern comma butterfly adults may be spotted flying around, even while there is still snow on the ground. This butterfly species is one of the earliest-emerging local butterflies since they spend the winter months as hibernating adults. Consider conserving or planting elm or hackberry trees to support their caterpillars.

Pests

• Spotted lanternfly (SLF) eggs masses are present on bark (and potentially a variety of other outdoor objects). Report any SLF egg mass sightings to the Maryland Department of Agriculture. Egg masses can be crushed or scraped off into a container of rubbing alcohol or hand sanitizer. Do not apply home remedies (like vinegar, dish soap, or boric acid) to egg masses laid on or around plants. Home remedies could potentially harm plants, wildlife, or the environment.
• Boxwood leafminer larvae (juveniles) may be present inside boxwood leaves. These overwintering larvae feed on the inner leaf tissue, resulting in discolored blotch-shaped mines. Larvae will begin to pupate inside the leaves and emerge as adult flies by late April. Infested branches can be pruned back by about one-third and disposed of to reduce the leafminer population. For further guidance on pruning, please refer to the "How to Prune Your Boxwoods" video.
• Certain spider mite species, like boxwood mites and spruce spider mites, will begin to hatch from overwintering eggs on their host plants (boxwood and conifers, respectively). For plants with known infestations, a horticultural oil spray (at a 1 to 2% rate) could be applied to suppress the mites once air temperatures reach 50 to 55°F for a couple of days. Do not use horticultural oil on blue spruce or it will remove the blue color of the needles.
• Crapemyrtle bark scale may be present on crapemyrtle or beautyberry bark, and are more visible this time of year on bare branches. Conserve natural predators of these scale insects (like ladybugs) by planting a variety of flowering plants nearby. Avoid pruning infested crapemyrtles too heavily, as this could lead to plant decline or death. Management options for heavy infestations can be found in the Introduction to Scale Insects page.
• Hemlock woolly adelgid adult females are present and preparing to lay eggs by producing protective white fluffy wax on hemlock branches. A horticultural oil spray (at a 2 to 3% rate) could be applied in early March to target adult females and reduce egg laying. Avoid overfertilizing hemlocks with nitrogen fertilizer, as excess nitrogen has been shown to enhance adelgid populations. For heavy infestations or large trees with hard-to-reach areas, hire a certified pesticide applicator.
• Ticks can become active once the temperatures begin to rise, even this early in spring. Wear light-colored long pants, long sleeves, and close-toed shoes. Tuck pants into socks, and tuck shirts into pants. Use insect repellents (age-dependent; check the product label for safe use), always after putting on sunscreen. Shower and check for ticks after being outdoors.
• Termite swarmers (winged/flying adults) can become active on warm, sunny days. Swarming is a natural dispersal occurrence, and does not guarantee that a structural infestation of termites is present in a home or building. Most swarmer termites die of dehydration if they fly indoors. Watch for any signs of an indoor infestation and contact a professional pest control company if you see indications of termite damage.

Look for galls (abnormally swollen tissues) on junipers, including the native Eastern redcedar (Juniperus virginiana), to reduce the spread of fungal rust diseases. Prune off and throw away any galls found on junipers as soon as possible, before the spore-producing tendrils are formed around early April. (The timing of spore release will be weather-dependent.) Juniper twig galls are most noticeable in wet weather, when the gelatinous orange spore tendrils are extruded. After the orange tendrils are produced, it is too late to prevent spore dispersal.

• Begin to fertilize houseplants again, as the increase in natural light (both in duration and brightness) will prompt them to grow.
• This is a good time to repot and divide houseplants. Use lightweight, well-drained soilless potting mixes that contain ingredients such as peat moss or coconut coir, vermiculite, and perlite.

Several species of insects are waking up from their winter dormancy inside homes. The earliest-appearing species are multicolored Asian lady beetle, marmorated stink bug, cluster flies, and boxelder bugs. No pesticides are recommended. They are harmless and can be swept up, vacuumed, scooped into a container of soapy water, or released outdoors.