A fall frost warning brings an urgent question: what should you pick today, and what can stay in the garden? The decision depends on the crop, its maturity, the expected cold and whether protection is realistic. One temperature threshold does not describe every garden.
Ontario’s cold-weather guidance for tomatoes and peppers notes that peppers can be injured by light frost, while the severity of damage depends on conditions. Look at your local forecast and the exposure of your own growing space, not only the regional average frost date.
Start with frost-sensitive crops
- Tomatoes: pick ripe fruit first. Before a likely damaging frost, consider harvesting mature green tomatoes that have reached full size and begun to lighten in colour.
- Peppers: prioritize usable fruit, because peppers are particularly vulnerable to cold injury.
- Cucumbers, melons and summer squash: these warm-season crops are cold-sensitive; harvest usable produce before a likely hard frost.
- Winter squash: harvest mature fruit before freezing weather damages it, and handle fruit gently to protect its skin.
- Tender potted herbs: harvest leaves or bring suitable containers indoors when cold will damage them.
The University of Minnesota Extension vegetable-harvest guide provides crop-specific harvest and storage advice; check it before applying the same storage rule to every vegetable.
Can green tomatoes ripen indoors?
Some can. Minnesota Extension’s tomato guide explains that mature green tomatoes may ripen indoors, especially when their green colour has started to lighten. Very immature, small green tomatoes may not develop good flavour. Set sound fruit in a single layer at room temperature and check frequently; remove any fruit showing decay.
Avoid storing damaged fruit with sound fruit. If a tomato or pepper has been visibly freeze-damaged, its storage quality may be poor. Sort promptly and follow appropriate food-safety advice before using questionable produce.
Which vegetables may stay longer?
Some cool-season crops, including kale, cabbage and mature root crops such as carrots and beets, are more frost tolerant than tomatoes and peppers. Tolerance still depends on variety, growth stage, soil and the severity or duration of cold. Do not assume all leaves or roots survive any freeze.
For crop-by-crop differences, see the University of Minnesota’s frost-tolerance categories.
When is it worth covering plants?
Row covers, well-secured frost cloth or a properly managed temporary shelter may protect plants during a short mild cold spell. They do not guarantee protection during prolonged freezing conditions. Keep covers from damaging plants, allow ventilation when temperatures rise, and avoid placing plastic directly against foliage.
- Check whether the forecast is a brief overnight dip or several cold days.
- Choose which plants still have enough usable crop to justify protection.
- Harvest the most vulnerable fruit before risking a loss.
- Remove temporary protection when daytime warmth makes overheating possible.
Record what the first frost changed
Note the forecast, the temperature you observed if measured, which plants were protected, what you harvested and what happened next. That information can help you choose crop varieties and planting times next spring. Try our harvest-records guide or end-of-season journal review.