Ah, there's a hint of coolness in the air — a promise of slowing down the frantic pace of watering, fertilizing, weeding and otherwise tending your garden. But there are a few fall tasks that will put your perennials and lawn to bed in good condition to survive winter and re-emerge for a healthy and beautiful garden next year.
The unanimous choice of garden experts for the most important task is cleanup. Removal of dead leaves and debris from around your perennials helps prevent disease and eliminate garden pests. "Fall is prime activity time for slugs, earwigs and sow bugs," says Master Gardener Marjorie Neal. Decaying vegetation on the ground gives them lots of places to hide. Fewer pests mean less pesticides and healthier plants.
Fall is also the perfect time to divide your overgrown bulbs and perennials, to move those that are in the wrong places, and to plant new perennials and bulbs for spring. Plants will have time to get established and build strong roots before winter, according to Esther Lee, customer service representative at the Grange Co-op in Medford. Be sure not to wait until the soil is too wet and soggy, or it will become compacted and get your new plants off to a poor start.
Spring-blooming perennials such as iris, daylily, hosta, Shasta daisies and lady's mantle can be divided into many new plants. "You'll know when they need it, because your parent plant will be weak and floppy, have a dead center, and isn't blooming as well as it should," says Master Gardener Marjorie Neal. More dividable perennials include forget-me-nots, lupine, hardy geraniums, yarrow and aster.
Plants with a mat of slender, interwoven roots can be gently pulled apart by hand. Plants coming from a large clump of tightly bunched roots can be carefully cut apart with a sharp knife. Be sure not to let roots dry out, and either pot up or transplant new baby plants. Mulch with a layer of good compost. When spring comes, enjoy them and remember all the money you saved.
Diseased foliage should be removed entirely to prevent spreading the disease. Examples include rust on irises, blackspot disease on roses, and powdery mildew on chrysanthemums. "Hot days and cool nights are perfect for powdery mildew," says Jana Larson, assistant manager of Ray's Garden Center in Ashland. If it's too bad, the entire plant should be pulled out and discarded, adds Neal.
Give perennials and your lawn a late fall feeding. "It's very important to give them a low nitrogen fertilizer," says Esther Lee, customer service representative at the Grange Co-op in Medford. High nitrogen will stimulate new and tender growth that won't survive winter. Temperatures in October or early November are still warm enough to apply a last feeding of 0-10-10 fertilizers. Look for "weed and feed" winter fertilizers specifically designated for lawns, Lee says. You can also apply a pre-emergent weed control on established perennial beds to prevent germination of weed seeds.
Cut flowering stems of perennials such as Shasta daisies, coreopsis, penstemon, asters, delphinium and daylily all the way to the ground or to the main body of the plant. "Take off old blooms and shear some of the foliage off lavender to make the plants bushier," says Larson, "otherwise they get weak and leggy." Include "dead-leafing" and removal of broken stems of coral bells, centranthus and lady's mantle, adds Neal.
Leave seed heads on some plants for winter interest, or as food for birds. "Blooms of 'Autumn Joy' sedum fade from pink to a beautiful reddish brown color," says Neal, adding they're "very, very tough and will withstand winter weather." Ornamental grasses remain attractive in winter and seeds of purple coneflower (Echinacea), black-eyed Susan (Rudbeckia) and salvias will help our feathered friends survive the winter. These can be cut back in late winter or very early spring.
Probably the second most important task after cleanup, is to apply a couple of inches of good quality compost around your perennials. "Most plants are weakened and die from lack of nutrition or poor soil [rather] than from the cold of winter," says Lee. Compost mulch not only improves the appearance of your garden, but also renews and nourishes the soil, which will nourish your plants next spring.
Even though we don't have severe ground freezes in winter, be prepared to protect your tender plants against high winds, a heavy snowfall or a hard frost, suggests Neal. Have on hand protective covers such as burlap, cardboard or bedsheets to protect that expensive tree peony you don't want to lose. Commercial products such as Frost Blanket are also available in 6 by 20-foot lengths at garden centers.
A little TLC for your lawn will reward you with a lush, green carpet next spring. In addition to the late fall weed and feed, removal of thatch is important; that is, removing the top layer of dead and dying plant material with a thatching rake will renew your lawn and allow nutrients to get through to the soil. Aerators remove plugs of grass to relieve compaction so air, nutrients and water can get to the roots. Machines are available at rental supply stores. These tasks are disturbing to your lawn and should be done early enough to give it time to recover before winter.
Last, but not least, don't neglect watering until the rains take over for you. Then you can really relax.