There's still time to plant. To ensure roots have plenty of time to grow, you want all new additions to the landscape -- including spring flowering bulbs and hardy garlic -- tucked into soil about 6 weeks before it freezes.
If you are planting late in the season, give your plantings a leg up by applying a thick mulch (up to 4 inches) of chopped leaves, pine straw, compost, or straw. This will insulate soil enough to postpone a freeze.
Make sure to keep an eye out for rodents. Mice especially love to nest in mulch through winter, and voles love nothing better than a thick cover to burrow beneath.
Continue to water plants, especially any new additions during the past year, until the ground freezes. This is vital if autumn rainfall is scarce.
Test Garden Tip: Dig planting holes now for live Christmas trees you plan to add to your yard next month. Save the soil you excavate, storing it in a place it won't freeze. Fill the hole with leaves until planting time. Use a tarp to keep leaves in place.
Fallen leaves provide overwintering shelter for insects. It's a good idea to allow a few leaves to remain beneath shrubs to harbor insects -- good and bad -- which can help feed hungry birds in spring.
On the other hand, leaves piled up against a shed, garage, or home can shelter and provide cover for pests -- including rodents -- seeking winter quarters. Remove these leaves. Chop them and use them as mulch, or add them to the compost pile.
Gather stakes and plant supports from the garden. Store them in a spot where they'll freeze to help destroy overwintering pests.
Fall can be a great time to cut back your perennials if you've got the time and energy to get it done. Make sure to leave 2-3 inches of the plant's stem to help protect fresh shoots from animal damage as they first emerge in the spring. It's also a helpful reminder of where plants are in the yard before they start to sprout.
Consider leaving some perennials standing that add interest to the winter garden -- either by their structure (Achillea, 'Autumn Joy' sedum) or by attracting birds to seed heads (coneflowers, black-eyed Susans).
Ornamental grasses should be left standing to protect their crown from a harsh winter.
Test Garden Tip: Pull spent annuals and toss them in the compost pile. Don't pull stems of self-sowing annuals so plants can seed serendipitously. Birds may also nibble on seeds.
Use the last of autumn's warmer days to take action for your garden's future.
Prepare new planting beds. You can easily start a new bed by layering materials over existing grass. Use a layer of cardboard or wet newspaper (three sheets thick) directly on top of grass, then layer on chopped leaves, compost, straw, shredded bark mulch, etc. Make each layer 4 to 6 inches thick. In spring, you'll discover rich composted matter ideal for planting.
Dress pots for winter interest. Stuff a plastic or otherwise crack-resistant container with eye-catching branches for a winter display. Clip evergreen boughs and berried branches, sticking them into soil. Add dried hydrangea blooms, ornamental grass seed heads, or canes with rose hips. Tuck in pinecones or hedge apples (osage orange) to finish the look.
Refresh mulch on planting beds. Mulch helps moderate soil temperatures, preventing extreme swings, which can create frost heave. When soil experiences freezes and thaws, it can actually push plantings out of soil. Plants typically prone to heaving are Heuchera, iris, and shallowly-planted small bulbs.
For most planting beds, 3- to 4-inch-thick mulch provides sufficient soil insulation. Apply a thinner layer (2 inches max) in areas where you expect self-sowing annuals and perennials to sprout in spring.
Test Garden Tip: Apply deer repellent to trees and shrubs that these pests typically browse in winter. The Swedish product Plantskydd will protect plants all winter long with just one application.
Test Garden Tip: Check hose connections, water wands, and quick connects for mineral deposits, especially if you live in an area with hard water. Remove deposits by soaking items in white vinegar. Alternately, soak a rag in vinegar and wrap it around the item. Follow the vinegar soak with a rag dipped in hot water.