By Judy Funderburk, Extension Master Gardener
Spring cleaning is not just for rugs and rooms. Planting beds need attention early in March. Many weed seeds will have already germinated on warm winter days. But, you ask, “is it a weed, or a plant?” Weeds of the Northeast by Richard H. Uva et al., and the University of Maryland Extension Weed Identification Photos are excellent identification sources.
Note that many of these annual weeds have poetic names—chickweed, speedwell, henbit or dead nettle, gill-over-the-ground or ground ivy, mulberry weed, hairy bittercress—but they are not at all poetic when they take over your garden. In fact, they need to be pulled before they set seed. Mulberry weed and hairy bittercress seed prolifically, and are two of the most invasive. Pull them by hand or use a hoe to cut off and discard the tops. Do not worry about leaving the roots because most winter weeds are annuals and will not resprout from the roots (although dandelions are perennials and the tap roots need to be dug up). Diligence in weeding now, when it is cool and there are no mosquitoes, even 15 minutes a day, can save you much effort and frustration later in the season.
Neatness counts, especially if any of your perennials had diseases last fall. Thorough cleanup of the ground is especially necessary in areas around roses and peonies where black spot, botrytis, or powdery mildew spores may have overwintered in the litter and can reinfect your plants. If you like the look, now is the time to give your beds definition. Use a sharp shovel to cut a clean, four-inch deep edge outlining the perimeter of your beds. Because you are edging a mostly “empty” bed, you can disperse the soil in place, back onto the bed, instead of having to cart it away.
Pruning is very plant specific. Cut back all grasses and most perennials, but not all. Wait until new growth appears to cut back soft “woody” shrubs and perennials, such as salvia, Caryopteris (blue mist shrub), Callicarpa americana (beautyberry), Perovskia (Russian sage), lavender, and rosemary. Many of these sub-shrubs can be pruned to 12–18” every spring to prevent legginess, but if you have space, prune less severely for a more open plant. Prune hydrangeas only if needed to remove winter-kill after buds swell, generally mid-April in Virginia.
Heavier pruning can be done after flowering, if desired. Wait to prune spring blooming shrubs, like azaleas and viburnum, until immediately after they bloom, but Cornus sericea (red-twig dogwood) should be pruned in early spring after the last frost, cutting out one-third of the oldest branches to encourage growth of bright red new stems for winter interest. Pruning is time-consuming and not always necessary. Prune for aesthetics, shaping, and plant health. Prune out crossing branches and winter-kill anytime, but in general the time to prune in Virginia is from early February to early April, depending on the type of perennial, shrub, or tree.
Soil tests are important. If you have not had your soil tested in a while, call Arlington/Alexandria, Virginia Extension Master Gardener Help Desk at 703-228-6414, any weekday between 9 and 12 for information on where you can get soil test boxes and instruction sheets. The test results from Virginia Tech will tell you which nutrients are lacking in your soil according to the use you have in mind, and the current pH level. Soil and pH deficiencies can lock up the availability or prevent absorption of nutrients by the plants. Top dressing beds with compost amends the soil by restoring trace nutrients and mycorrhizae that keep the soil and plants healthy. Applying two inches of shredded leaf mulch helps feed soil microorganisms, keeps many weed seeds from germinating, and keeps moisture and temperature levels in your beds more even.
After taking care of the “spring cleaning” activities appropriate for your garden, you are ready to plant. The caveat here is that not all the plants available at local nurseries or farmer’s markets are suitable for planting in the early spring. Flowering plants that will give you early spring color and can tolerate March temperatures and light frosts include pansies, snapdragons, petunias, primroses, dianthus, and calendulas. Experiment with brightly colored lettuces or Swiss chard planted in ornamental beds. Directly sow seed or dig seedlings into prepared soil. Try Merlot, Red Sails, Freckles, Australian Yellowleaf lettuces and ‘Bright Lights’ Swiss chard for interesting, edible foliage—the essence of local food! Sugar Snap peas can be planted in late March for delicious munching from vine to mouth. Plant them around a wide trellis or teepee structure so they have some support. Ignore tempting pots of impatiens, geraniums, basil, and other warm season annuals which hate cold feet until at least mid-April or early May.
One more caveat: in the mid-Atlantic region, the best time for planting shrubs and trees was last fall! But, when planting newly purchased shrubs and trees in the spring, try to get them in the ground as soon after the last frost date as possible. Websites vary widely as to what that is; sometime between March 29 and April 15. Know that spring planting of trees and shrubs means you must give them extra care and water attentively at least through the first year.
May your plants enjoy their “spring clean” home. May you enjoy their growth.