Here are some tasks to get your garden ready for winter.
By waiting until now to prune your shrubs, you avoided stimulating new growth, which can lead to winterkill. But now it's time to prune certain deciduous shrubs to ensure they remain ornamental, healthy and manageable throughout the growing season.
The only practices necessary for some of these plants are cutting broken branches and dead wood, as well as light, corrective pruning. Others can be cut to the ground. Be sure you know flowering and growth habits before pruning. Two books I count on are "The Pruning Book," by Lee Reich (Taunton, 1999) and "Pruning Trees, Shrubs & Vines," by Karan Davis Cutler (Brooklyn Botanic Garden Handbook No. 176, 2003).
Shrubs to prune now are those that leaf out in spring and form flowers on the stems growing the same year. Hard pruning will prepare them for next year because the flowers and berries form on the new growth. Examples of shrubs that flower on the same year's growth are butterfly-bush (Buddleia davidii), Annabelle hydrangea (H. arborescens), chastetree (Vitex agnus-castus) and purple beautyberry (Callicarpa dichotoma). They can be cut after they lose their leaves, until just before spring growth begins, and will renew quickly in one season -- provided they receive six to eight hours of sun. If your plant is slow to establish, wait to cut it hard and evaluate whether it has enough light. These shrubs can be cut to any height, but for flowers, the preferable way is to cut the plant hard, leaving 12- to 18-inch woody stubs.
Wait until spring to prune shrubs that offer winter interest. Red- and yellow-twig dogwoods (Cornus sericea and sanguinea) are examples of such plants. These fast growing, shrubby dogwoods should be cut to the ground before spring growth begins. Crape myrtles have a handsome exfoliating bark that gives the trunks a showy appearance all winter. Wait to prune them until after spring growth begins.
Certain shrubs shouldn't be pruned until after flowering because the flower buds for next year form on stems that grew this season. Cutting them now would sacrifice the flowers. Examples are bigleaf hydrangea (Hydrangea macrophylla), forsythia, lilac, weigela, deutzia, flowering quince, pearlbush (Exochorda racemosa), winter flowering jasmine and spiraea. They can be pruned hard right after flowering and should not be cut again until after next year's flowering. Many of these plants can grow for several years until they become unruly again.
Azalea, pieris, camellia, leucothoe and many other spring-to-early-summer flowering shrubs become most showy when, after flowering, you cut a branch here and there as needed for the shape or health of the plant and do no other pruning. Prune to another branching stem or, if there is no branching, you can cut the stem at the ground. My preferred method is to cut branches selectively, one at a time.
Don't use electric trimmers to prune, unless it's simply too time consuming to do it any other way. Sheared shrubs will create an unhealthy excess of foliage and stems when they regrow.
After evaluating and pruning, look to the rest of the landscape. If the leaves have fallen from deciduous plants, it's time to complete your fall cleaning.
Leaves covering the lawn will suffocate it, so they should be raked and put in the compost pile. Debris should be cleared from areas where it will detract from, or cover, winter and spring interest in the garden. Excess landscape litter can also get soggy and suffocate or destroy the ornamental value of low plantings.
Keep the following plants clean of debris to provide winter and spring interest. Hellebore is always my first choice because it is an evergreen perennial that flowers in winter. Bath's pink dianthus holds its blue-green foliage all winter and displays fragrant flowers in spring. Russian sage (Perovskia atriplicifolia) holds its gray appearance and fragrant stems into winter. Candytuft (Iberis sempervirens) is an evergreen, low-growing (six inches to 10 inches high) wide spreading (three feet or more) sub-shrub that flowers white through most of April. Also, clear areas now where small winter flowering bulbs will surface before spring cleanup. For example, in February, winter aconites, jonquils, snowdrops, crocuses and foliage of spring bulbs are emerging.
If there are weeds you wish to impede, and have no ornamental plants growing in that location, cover the area with a thick layer of ground-up yard debris. A rotary power mower set to cut high will grind light layers of debris. Be sure there are no bystanders, and use a mulching-type mower that has no discharge chute on the mower housing. If you have a lot of debris, rent a chipper shredder. It's efficient for grinding litter into mulch-size particles that can be spread over the beds or added to your compost.
Leaving debris over the beds is our manipulation of nature. When leaves and small stems drop to the ground and decay, the plant debris makes an excellent fertilizer, such as grass trimmings on lawns and needles under conifers. Dry leaves laid over beds will also insulate and protect early spring plants during the winter, as long as they are removed when it is time for plants to perform.
Using trash bags, dispose of leaves and dead branches from woody shrubs or other plants that have died from fungus or root rot diseases, and include perennials whose foliage displayed mildew or wilt due to spring and summer fungus. Include vegetables in the nightshade family, such as tomatoes and peppers. If you are unsure whether a disease or insect caused damage or plant loss, discard the debris rather than composting it.
After raking or blowing off leaf debris where necessary, cut down, or cut up, the perennials as they freeze back. Using a string trimmer, hand sickle, hedge trimmer, lawn mower or hand pruner, cut the top growth of your perennials into as many pieces as possible. Allow 1 inch to 2 inches of stubble from each plant to stick out of the ground. Unless it is unsightly, let the debris lay where you chopped it. It's nutritious, and, as with many plants, you are thickening the stand by helping it spread its seeds into that location. Such is the case for black-eyed Susan, purple coneflower, liatris, penstemon, forget-me-not and other wild flowers.
Once problem plants have been discarded and everything else cut back, it's time to mix in organic material -- plant leaves, partially decomposed ornamental bark mulch from the past growing season and compost you made over the summer. Compost is one of the panaceas of the garden.
Improving soil drainage and aeration with organic material in the form of compost is known to reduce populations of soil-borne pathogens. Hoe or cultivate a minimum of four inches into soil between your plantings -- the deeper the better -- trying to disturb roots of existing plants as little as possible. Mixed with the existing native soil, compost makes topsoil, and it's easy to make.
To make compost, put organic material into a bin or a pile about four feet square. Don't add diseased plants or meat scraps. Arrange in alternating layers -- six inches of leaves and twigs, then six inches of grass, weeds, and other green materials. Fill a bucket with soil and a little agricultural limestone; sprinkle mixture over each layer to a height of 3 to 4 feet. Keep the pile moist, turning every five to six weeks, when not frozen, and it will be ready by May.
Joel M. Lerner is president of Environmental Design in Capitol View Park, Md. E-mail or contact him through his Web site, www.gardenlerner.com.