Some gardeners are relieved at the onset of fall, especially if pests have been a plague, if rain has been too scarce or too abundant and if the old arthritis has been acting up.

However, I think fall is a terrific time to garden.

The weather is generally good, with warm days and cool nights, ideal for plants that need to concentrate on building root bases. The pests slack off or disappear, and the bright fall colors are a real incentive to be outdoors.

Fall is a great time to plant (even vegetables!), divide, prune, protect, feed and generally get a head start on spring.

Things to plant include perennials, trees, shrubs and spring bulbs. Many perennials and deciduous trees and shrubs show the most vigor in their first year when planted this month.

Peonies are among plants that do better with a fall head start; it's also the time to transplant them. If your peonies have had prolific foliage but don't bloom, they may be planted too deep. Dig them up and make sure the eyes -- the red bud spikes that will be next season's growth -- are within half an inch of the surface. Peonies generally don't need dividing, but if you want more, wait until the foliage turns brown, then move root pieces that are about four to five inches long and have four to six buds on each.

To divide and transplant perennials, dig up or slice off reasonably large pieces of roots, three to five inches around and, depending on the depth of your roots, four to eight inches deep. Dig a new hole, add compost to the existing soil, place the division into the soil, and water. It is usually that simple.

Another method is dividing the pips, bulbs, corms, roots or rhizomes by hand, carefully cutting where necessary. This yields more plants and can, as in the case of day lilies, irises and dahlias, produce larger, showier flowers. Divide dense stands of lily-of-the-valley every three to five years for best flowering. If your perennials are blooming now, wait until March or April to divide them. Autumn joy sedums, asters, ironweeds (Vernonia), boltonias and chrysanthemums are a few of the perennials that should wait for early spring dividing and transplanting.

Among bulbs, daffodils can be planted now, but November is a better time to plant tulips. As the ground gets cooler and we get a frost, it will be time to dig up tender bulbs, such as dahlias and canna lilies, and store them to grow again in March. Keep at a minimum of 37 degrees. Make sure that the stored tubers are cleaned of all soil and barely moist to discourage fungal infections. Store them in vermiculite or dry peat, in paper bags in a cool space such as a garage, basement or crawl space.

As for vegetables, if you plant now, you can get excellent crops of such cool-weather plants as spinach and kale, Brussels sprouts and cabbage, turnips, carrots and lettuce. Some of the root crops will do well into November.

Fall is a good time to plant deciduous shrubs and trees. Evergreens, such as spruces, pines and most other conifers, survive the winter well when installed now. Success might be more assured for broadleaf evergreens, such as hollies and azaleas, by planting in the spring before growth begins.

To prepare your site for planting, dig a wide area. Add 20 to 30 percent organic material to soil, and incorporate it over as wide and deep an area as practical. Feeder roots spread horizontally over a long distance, and even the biggest hardwoods absorb nutrients largely from the top two feet of soil.

Once the area has been prepared, dig the planting hole. Place the ball so that the root collar, the flare at the base of the tree, is several inches above or at the soil line. Roots grow horizontally underground from this point. The flare must be above ground. Don't mulch against the flare or let any soil pile against it more than an inch or two, or it could rot bark, increase susceptibility to disease and insects, and interrupt nutrient circulation. Set the root ball on undisturbed or packed soil so it doesn't settle.

Be sure trees and shrubs are perpendicular and on firm soil. If the roots are wrapped in burlap, fill the hole about a third of the way, enough to support the root ball. Then remove the ropes and pull back and fold down the burlap from the top third or more of the ball. If a tree is in an open wire holder, bend the wire down and cut into the burlap, but leave the basket on. Fill the hole, tamping soil firmly in place.

When you install a plant that comes in a container, remove it completely from the pot. Pull the roots out from the soil in the pot. If they are too tightly woven, make vertical cuts with a knife down the roots in three to four places around the ball.

Water newly installed plants immediately, soaking them thoroughly. Form a basin around the edge of the root ball to catch rain and irrigation water. Water weekly if there is no rain. Don't fertilize newly installed plants, but mulch trees and shrubs with two inches of composted leaf mold that will hold moisture and protect the roots through winter.

(Fall is a good time to start or enhance a compost pile, by the way. As you remove spent annuals and trim perennials that have quit blooming, add the organic matter to the pile. Add only disease-free plant matter.)

Research shows that trees and shrubs establish better if their tops are allowed to blow in the wind. Use stakes and wire only on newly planted trees with bare roots.

If you plant shrubs, trees, bulbs or other perennials such as camellia, crape myrtle, Carolina jessamine, canna lily, ruscus or agapanthus that are marginally hardy to this region, prepare to help them through the winter with mulch and burlap wraps.

Although the traditional time to prune trees is after their leaves fall, I do it as the weather cools and the trees are still in leaf. This helps evaluate aesthetic appeal. As you make cuts, you can stand back and assess what they look like in leaf.

On mature trees, remove side branches to make their canopy six to eight feet or higher above the ground. That way you can see under-story plantings and structures. Most trees should be the canopy of the landscape. Keeping limbs higher also makes mowing or walking in the beds easier.

Don't cut the branch collar, which is similar to the root collar at the base of trees. It's a slightly flared area at the base of most branches, about 1/4- to one-inch long, depending on branch size, and slightly wider than the rest of the stem. Experts have learned that wounds heal faster when this branch collar is left uncut.

Prune no more than 25 percent of growth and cut dead wood, which is easier to see on a tree in leaf. Remove inside and crossing branches. Prune high with pole pruners. Work that requires climbing should be left to professionals.

Do not prune shrubs now. Pruning can stimulate new growth, making the shrubs more susceptible to winter damage. Never prune wet shrubs and trees; it can help spread disease. Pruners should be cleaned with bleach and lubricated with light oil, such as WD-40, after cutting diseased or dead wood.

Fertilize trees, shrubs and lawns using a surface application of a granular fertilizer with about a 10-6-4 analysis or close equivalent over root systems. Reportedly, organic or synthetic fertilizers work equally well to supply nitrogen, phosphorous and potassium. Follow labeled instructions. If you don't fertilize trees by the end of September, wait until March or April.

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.

Peonies are among the plants that do better with a fall head start. Many perennials, deciduous trees and shrubs show the most vigor in their first year if they are planted in September.