How to cover plants for frost

Frost can kill tender plants in one night. A cover holds in the warmth the soil gives off after dark and keeps frost off the leaves.

Words to know

Tender plant:: A plant frost damages or kills: tomatoes, peppers, eggplant, basil, beans, squash, cucumbers, melons, sweet potatoes and most summer flowers.
Frost:: Ice that forms on leaves on clear, still nights. It can form when the forecast low is a few degrees above 32°F, which is why the app warns at 36°F.
Frost cloth:: Light fabric sold for covering plants, also called row cover. An old bedsheet or blanket works too.

In the afternoon, water the soil if it's dry. Damp soil holds more heat.
Before dark, cover the plants with a bedsheet, blanket, frost cloth, or an upside-down bucket, pot or box.
Let the cover reach the ground on every side and hold the edges down with bricks or rocks. The warmth comes up from the soil, so the cover has to trap it.
If you can, prop the cover up on stakes so it doesn't rest on the leaves.
Take the cover off the next morning once it's above freezing, so the plants get light and don't overheat.

✕ Plastic sheeting touching the leaves — the cold passes straight through it. Only use plastic over a frame or on top of a sheet.
✕ A cover that stops short of the ground.

Kale, cabbage, broccoli, spinach, lettuce, peas, onions and garlic handle a light frost without a cover.
Covers add a few degrees. On a hard freeze (below about 28°F), pick anything ripe first and expect tender plants to be damaged.

Based on standard guidance from U.S. university extension services, including Cornell, the University of Minnesota and Oregon State.