Monitor Indoor Plants
Check the plants you brought indoors last month for insects, munched leaves, fungi, disease, gnats, or slugs in the soil. If there's an infestation, be sure to examine other plants nearby. Treating a small problem now could eliminate a bigger problem later that might require more toxic control. Identify the insect and select pest-specific, least-toxic treatment to start. For example, for white fly I'd spray leaves, stems, and soil with insecticidal soap three or four times to kill the adults. If pests persist, I'd switch to Neem oil applied as directed. Usually one or two doses of Neem will eliminate a wide range of pests at various life stages.
Remove Leaves Trapped Low in Shrubs
Though it will take some bending, stooping, or kneeling, remove leaves and debris stuck in the lower branches of azaleas, hollies, hydrangeas, and other shrubs. Scale and fungi (and gnawing critters such as voles) easily overwinter in trapped, matted leaves at ground level. Left in these protected spots, they'll set up housekeeping on branches and the undersides of leaves, and promote branch and stem rot. An ounce of prevention ...
Grapple with Garlic Mustard
Invasive garlic mustard is one of the few plants still green when the snow falls. Its scalloped-edged, deep green, wavy leaves make a good target for late-fall and early-spring removal -- when many other plants (including natives) are dormant. Hand-pulling now or digging to remove the upper half of the root will stop buds from sprouting next spring. Burning off the foliage with a flame torch is another option. This will be a long war, though. It can take three to five years of burning, hand-pulling, and spring cutting to get this invasive under control. Herbicide application is also an option now because garlic mustard is visible, growing, and vulnerable. Most native plants are dormant so they won't be damaged. Recommended application is 1 to 2% active ingredient solution of glyphosate on the foliage of individual plants and dense patches while the temperature is greater than 35 degrees F.
Don't Be Too Tidy
Wildlife and butterfly caterpillars appreciate brush piles, downed wood, rotting trunks, and decaying stumps as winter shelter. So keep them where you won't mind the "natural" look. A smidgeon of leaf litter on a garden bed is fine; the bits will accumulate around perennials and help buffer their crowns through freeze/thaw. Limit it to a dusting of loose leaf litter, not clumps of matted leaves.
Carefully Dispose of Garden Chemicals
Dispose of opened, unused herbicides and pesticides according to local or state laws. Do not pour leftover pesticides and herbicides down the sink, into the toilet, or down a sewer or street drain. Pesticides may interfere with the operation of wastewater treatment systems or pollute waterways. Many municipal systems are not equipped to remove all pesticide residues. Pesticides in waterways may harm fish, plants, and other living things.
For proper disposal, check with your local solid waste management authority, environmental agency, or health department about your community's household hazardous waste collection program. For more information, call 1-800-CLEANUP. Also see: http://www.epa.gov/pesticides/regulating/disposal.htm.