Gather the Last of the Harvest
Frost can hit any day now, so keep a close eye on the weather forecast. When frost threatens, harvest the last of the warm-season vegetables -- tomatoes, beans, and peppers. Freeze, can, or otherwise preserve produce you won't be able to use within a few days. Dry herbs by placing them in a warm oven until they're crispy.
Collect Fall Decorations
Collect flowers for drying, cut grapevines, gather seedpods, and prune berry-laden branches to use in fall decorations. Plan ahead and gather materials you can use to make holiday gifts; for example, press late-season flowers now for framed collages.
Bring Houseplants Indoors
Begin preparing houseplants for the move indoors. If possible, acclimate them over the course of a few weeks to the dryer, warmer, darker indoor conditions by placing them in a transition area such as a porch. Inspect plants for pests before bringing them indoors.
Weed the Garden
Any weeding you do now will reduce many times over your weeding chores in the spring. Pull weeds before they set seed, and you eliminate the task of pulling all those little seedlings. A single weed plant may set hundreds, or even thousands, of seeds, so don't delay.
Adjust Soil pH
Fall is a good time to test your soil. By adding any necessary amendments now, they'll have time to break down over the winter. Cooperative Extension offices do soil tests for a nominal fee, and the test results include recommendations for improving the soil. At the very least, test your soil's pH. Most plants prefer a slightly acidic soil with a pH of 6.5 to 6.8 (a pH of 7 is neutral). Our soils tend to be acidic and require the addition of lime to "sweeten" the soil.