Plant flower bulbs now for drifts of spring bloom. Best bets for naturalizing (bulbs that come back year after year) are bluebells (Scilla), crocuses, daffodils, grape hyacinths (Muscari), Star of Bethlehem (Ornithogalum arabicum), and species tulips. Hyacinths and hybrid tulips are stunning but may last only a few seasons. Most bulbs have a flat end and a pointed end; plant the pointy end up. Plant about twice as deep as each bulb is tall, spacing them 6 to 12 inches apart. For an indoor show, plant two or three 10-inch-wide bowls or low pots with paperwhite narcissus, spacing bulbs 1 to 3 inches apart. Put containers on a frost-free porch or in an unheated room. When flower buds emerge in a few weeks, display pots inside during the day, but set them back onto the porch or cool room at night (cool nights keep the growth from stretching out and falling apart as flowers open).
Plant hardy groundcovers now and they'll send out roots during winter and put on a strong burst of growth when the weather warms in spring. Check out epimediums ― they do the same job as English ivy (they're low-growing and thrive in partial shade) but are superior for flowers, leaves, and nonaggressive garden manners. Many also turn an attractive bronzy color in fall. For sunny places with soil that's well drained but low in fertility, try kinnikinnick, thyme, or a groundcover form of Ceanothus or Cotoneaster. For woodland areas, consider Asarum caudatum, Epimedium, Japanese spurge (Pachysandra terminalis), or Vancouveria.
The best soil for annual flowers and vegetables is well tilled and well endowed with organic matter. To keep it that way, sow seeds of cover crops such as Austrian winter field peas, crimson clover, and tyfon greens by early October. Grow them through winter, then till them under in April or May before you plant next summer's garden.
To spruce up your fall and winter garden, look for plants with autumn berries, trees and shrubs that have great fall color, and evergreens with golden foliage, which is especially effective under cloudy skies.
You can still buy fall-flowering asters, 'Autumn Joy' sedum, mums, ornamental cabbage and kale, pansies, and violas now. But plant for spring too: The discounted, played-out columbines, coreopsis, daylilies, and Shasta daisies you buy now will delight you when they flower next summer.
Check bearing plants every few days. Pick everything that's ripe and, just as important, everything that's flawed or shows signs of decay. Likewise, harvest all tomatoes that have started to turn from grass green to yellow or red; bring them inside to finish ripening on the counter.
Give fuchsias their last feeding in early October, then let them wind down. Before frost, bring containers inside (a cool, dark basement or frost-free garage is fine) or cover plants in the ground with mulch. Zones 1-3: Bring fuchsias inside for the winter.
Care for roses. Allow a few hips (seedpods) to form, as that process completes the flowering cycle and ushers plants into dormancy. If you've never grown roses for hips, shop for them now so you can spot species and varieties that produce showy ones: Try 'Bonica', Rosa glauca, and sealing wax rose (R. moyesii).
As you clean out the summer garden, run the lawn mower across the debris (avoid stringy material or woody stems more than ¼ inch thick), then pile it in layers. Alternate a 4-inch-thick layer of green debris (chopped weeds and grass) with a 4-inch-thick layer of brown material (straw, manure, or shredded autumn leaves). Make the pile about 4 feet wide and 4 feet high. Turn the pile with a garden fork every week or two, and keep it moist. By next spring, rich, black compost will be ready for use as soil amendment or high-grade mulch.
Plants need about an inch of water per week through fall. If rain doesn't supply it, you'll need to water. Drought-stressed plants are far more likely to be damaged during cold winters than healthy ones. Don't forget to water plants growing under house eaves where rain doesn't reach.