Season extension: cold frames, row cover and hoop houses
Last reviewed September 2026 · written from public-domain USDA/NOAA data and Cooperative Extension references — see how we source data
A few degrees and a few weeks at each end of the season are easy to gain with covers. None of it needs heat or electricity.
Floating row cover
Lightweight spun fabric laid over hoops or straight on the crop. Lets in light, water and air. Light grades give about 2–4°F of frost protection and keep out flea beetles, cabbage worms and carrot rust fly; heavy grades give 6–8°F but cut more light.
The cheapest, most flexible tool here. Weigh the edges down and leave slack for plants to grow into.
Cold frames
A bottomless box with a clear sloped lid, facing south. Good for hardening off seedlings, overwintering hardy greens, and starting spring sowings weeks early. Vent it on sunny days — it can overheat fast even when the air is cold.
Low tunnels and hoop houses
Low tunnels are row cover or greenhouse plastic over hoops across a single bed. A walk-in hoop house (high tunnel) is the same idea at scale. Plastic adds more warmth than fabric but must be vented and does not let rain through.
Stacking methods multiplies the effect: a hardy crop, under a low tunnel, inside a hoop house can crop through a cold-winter month it otherwise could not.
What to grow under cover
Cold-hardy crops that keep going in low light: spinach, kale, mâche, claytonia, arugula, scallions, carrots left in the ground. Growth nearly stops below about 10 hours of daylight, so plant to near-full size before midwinter and harvest through it.