Northern & Central Midwest
Plant Fall Greens
Sow fall greens such as mustard, Chinese cabbage, spinach, Swiss chard, and lettuce. Most of these greens will tolerate light frosts, and some, like kale, taste even better after getting frosted. Also, radishes are a quick enough crop to mature before the days get too cold.
Control Cabbage Butterflies
Keep a close watch on broccoli, cabbage, Brussels sprouts, and kale for cabbage butterflies. Apply Bacillus thuringiensis (Bt) every ten days or so to keep a healthy population of bacteria going on the leaves to kill the butterfly larvae. Caterpillars that ingest the bacteria quickly stop feeding and die. Bt is harmless to humans and animals.
Continue saving seeds, making sure they're absolutely dry before putting into storage. The best storage methods keep them cool, dark and dry such as in inexpensive canning jars with new seals or plastic zipper bags. Keep them in the refrigerator or in a dark, cool spot at floor level.
Controlling Tomato Diseases
Continue pulling off and disposing of diseased tomato leaves. Keeping the area cleaned up will help prevent infection of next year's crops with fungal diseases such as early and late blight. If your compost doesn't really get hot enough (130F) to break done these diseases, dispose of the leaves at your city's compost facility or bury them somewhere away from the garden.
Storing Carrots and Beets
Bring in hay bales for mulching carrots and beets late in the fall. These root crops can survive a good portion of the winter in the ground as long as they're mounded up with hay bales. Leave the hay baled so you can just lift it off to harvest. Carrots, in particular, taste sweeter after a good freeze.