Guide
Even when you plant after your last frost date, a surprise late freeze can still threaten tender crops — frost dates are averages, not guarantees. The good news: when the forecast turns cold, a handful of simple techniques can carry your garden through the night. The key is to watch the forecast and act before temperatures drop, not after.
A lightweight fabric row cover is the most reliable frost defense. Draped over plants and anchored at the edges, it traps radiant heat rising from the soil and can offer roughly 4–8°F of protection depending on weight. Supported on hoops so it doesn't crush foliage, it's easy to leave on for a cold snap and remove once the danger passes.
For a few precious seedlings, a cloche — a bell-shaped cover, an inverted bucket, or a cut-down gallon jug — creates a pocket of warmer air around each plant. Set covers out before dusk to capture daytime warmth, and remove them in the morning so plants don't overheat or suffocate.
Moist soil holds and releases far more heat overnight than dry soil. Watering the ground (not the leaves) in the afternoon before a predicted frost warms the root zone and moderates the air just above it. This is a free, surprisingly effective tactic in spring and fall shoulder seasons.
A cold frame — a bottomless box with a clear lid — acts like a miniature greenhouse, buffering plants against cold and extending your season by weeks on both ends. A low tunnel (hoops covered with plastic or heavy row cover) does the same over a whole bed and is ideal for hardy greens.
A layer of straw, shredded leaves, or other organic mulch insulates the soil and protects roots and crowns from freezing. It's especially valuable for overwintering hardy crops like garlic, carrots, and kale, and for buffering perennials through cold snaps.
| Category | Examples | Frost response |
|---|---|---|
| Tender | Tomatoes, peppers, basil, squash | Killed by any frost — protect |
| Tolerant | Lettuce, cilantro, chard | Survive light frost with cover |
| Hardy | Kale, spinach, carrots, broccoli | Shrug off light frost unprotected |
Focusing your effort on the tender crops saves time — hardy vegetables often improve in flavor after a light frost and rarely need covering.
The simplest protection is prevention: don't rush tender crops into the ground. Adding a one- to two-week buffer past your last frost date dramatically cuts the odds of a damaging freeze. The frost date planner shows your exact frost windows so you can time plantings with confidence.