Reference
Winter and Cold-Hardy Crops for Season Extenders
The short answer
Cold frames and unheated low tunnels create a warmer microclimate that lets cold-hardy, cool-season vegetables keep growing well past the first frosts. Reliable winter and late-season crops include spinach, kale, beets, carrots, lettuce, radishes, and scallions, with the toughest greens surviving even under snow.
The colder your climate, the shorter the list of dependable crops, and growth slows sharply in deep winter. Adding a second inner layer, such as a row cover over a bed inside a tunnel, buys extra protection during the hardest cold.
Dependable cold-hardy crops
- Spinach
- Kale
- Lettuce (cool-season types)
- Beets
- Carrots
- Radishes
- Scallions
Growing through cold
Inside a cold frame or tunnel, temperatures often stay just right for cool-season vegetables even with snow outside. For the coldest stretches, cover a row within the tunnel with an extra layer to add protection.
→ In the coldest zones only a handful of the hardiest greens and roots harvest dependably all winter; growth largely pauses in the darkest, coldest weeks.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- University of Minnesota Extension — Extending the growing season — Cool-season crops like spinach and lettuce grow later under cold frames and tunnels.
- University of Georgia Extension — Extending the Crop Season: Unheated Spaces (C1027-14) — Unheated tunnels and frames support cool-season crops into cold months.