The ideal time to plant fall crops is late summer, when soil temperatures are still warm. But if you miss the window of opportunity, and the soil is cold, start the seedlings indoors as a container garden, then move them outside to a cold frame.
Cool-weather veggies vary in hardiness. Among the most tender of the lot, lettuce grows best at 50 to 60 degrees F; growth slows as temperatures drop. Keep it in a cold frame; when the temperature falls below 30 degrees, lettuce is in trouble.
Kale (above: Siberian kale) produces even when temperatures are in the low 20s, and it can survive until temperatures dip below 5 degrees F.
Year-round Herb Garden
Parsley (pictured with purple kale, another winter garden favorite) is a cold-tolerant herb. Bring some indoors to keep your kitchen-garden growing through the winter; you can also try leaving some outside, in a cold frame or covered in snow. Another cold-tolerant, kitchen-garden plant: chives.
Grow For Looks, Not Taste
Ornamental cabbages and kales are genetically the same as the varieties you grow as edible veggies, but while the ornamental forms are edible, they don't taste as good as their garden-variety cousins. Still, they're often used to "dress up" a dish. The ornamental varieties hold well into winter, their colors intensifying with frost. If they've been gradually acclimated to the cold, they tolerate temperatures as low as 10 degrees F.
Nasturtium is a cool-weather, edible annual. Try seeding and growing it indoors as a fun and colorful winter gardening project.
Put Your Veggies Under Wraps
A cold frame protects fall veggies from frost and, depending on its construction, offers temperatures at least a few degrees warmer than the air outside. During warm spells in the fall season or if the cold frame is sitting in the direct sun, roll up the poly film on the sides of the cold frame and attach it with tape to allow more air flow through the frame and prevent the veggies from cooking inside.
An easy-to-assemble cold frame: place four bales of straw in a rectangle and set an old window over the open area in the middle.