Fall cleanup close at hand> Garden chores in autumn may help plants survive winter

Even if one doesn’t notice how late dawn is and how early dusk arrives these days, there would be plenty of clues from nature that the days are growing shorter and the natural world is readying to slip into dormancy.

The mums are starting to bud up and bloom with their second brilliant display; the tips on the sumac are starting to turn red as the leaves prepare to ship nutrients to the roots for winter storage; there are noticeably fewer birds in the yard and garden, as some have flown south in search of balmier weather.

Although a killing frost won’t happen for a few weeks, early September is the time most gardeners begin to think about garden cleanup. Pulling up annuals, stripping vegetable vines of their fruits and seeding ground with cover crops are all common elements of fall garden chores.

Cleaning the annual or vegetable garden is simple in many ways: pull it up, till it under and seed it down or cover it with mulch. The perennial garden, however, needs special attention this time of year.

While there is still time to plan before the first killing frost descends upon us, organize your fall gardening efforts so that you may prepare your perennial bed for the long winter ahead. Despite what some believe, fall is not really for fertilizing or planting. It may be time for dividing the minority of perennials that deeply resent being divided in spring — peony, poppy, cimicifuga and allium to name a few — but generally speaking, it is not a time to start new gardening endeavors. It’s a time to concentrate on putting to bed the perennials that have survived the summer.

Always avoid adding high-nitrogen fertilizer to the garden at this time of year. Plants are trying to put away food for winter storage, and adding fertilizer signals them to initiate new growth, an activity that will surely weaken their chances for winter survival.

A simple formula for cleaning up around plants that die back to an underground crown can be followed each fall. A killing frost can occur in central Maine anywhere from mid-September to the middle of October. After that date, garden cleanup begins.

First, clear away all the dead leaves and plant material around each perennial. Cut back the stems of each plant so that they are 3 to 4 inches tall. Again, clear away the dead debris. The remaining stalks will minimize disease and insect problems and will help you identify where desirable plants are, come spring.

After the garden has completely frozen, but well before the first snowfall — usually sometime around Thanksgiving — it will be time to layer in some mulch over the dormant perennials. Keep in mind that the ground should be completely frozen to avoid “sealing in” wetness with the mulch, thereby creating prime conditions for disease and plant rot.

The main point of applying a mulch is to protect plants from repeated thawing and freezing that can occur when the sun’s rays warm the soil during winter days, and when the soil heaves as it freezes again at night. A mulch layer buffers the soil against these sharp variations of winter temperatures, protecting the plant from possible damage to its roots.

To mulch the perennial bed, shovel a 2- to 3-inch layer of compost, shredded leaves, or pine needles over the entire area. Keep in mind that each mulch has its own pH. Maple leaves, for example are alkaline, whereas oak leaves and pine needles are acidic. Over time and repeated applications, mulches may change the pH of the soil, which in turn may affect plant growth.

Shredded mulches and compost have the added benefit of acting as soil amendments in spring. Once the mulch is pulled away from where the plant has begun to emerge from the soil, it may be worked into the garden soil, providing a great source of nutrients for plant growth.

Naturally, there are some exceptions to this simple cleanup formula. Some woody perennials, such as sage, should not be pruned in fall. These perennials, as with shrubs and trees, should be left to prune in spring, when new growth is well under way. Mid-June is usually a good time to cut out the old and dead tissue on woody perennials and shrubs.

Attention to the needs and growth of individual plants will provide clues on how to tailor fall care so that each plant is well-prepared for winter. And of course, there are no guarantees. Let’s hope Mother Nature provides her own mulch cover, rather than a brutal and exposed winter.

In a strange way, we should welcome a hardy layer of snow — it’s a misadventure to those who must shovel it, but it is winter’s comfort for the plants whose summer show awaits below.

Diana George Chapin is the NEWS garden columnist. Send horticulture questions to Gardening Questions, c/o Maine Weekend, Bangor Daily News, P.O. Box 1329, Bangor 04402-1329. Selected questions will be answered in future columns. Include name, address and telephone number.