Tomatoes & Peppers Before Frost: Saving the Last of the Crop

Reading the forecast

Nights below 4°C are a warning — light frost is possible at ground level even when the official forecast says 4°C. Tomatoes and peppers stop ripening once temperatures drop below 10°C consistently, even without actual frost. The plant is still alive but no longer pushing fruit toward red.

The first hard frost (below -2°C) kills tomato and pepper plants outright. Anything on the vine when that frost hits is lost.

Buying time with covers

A single cold night when warmer weather is forecast for the rest of the week is worth fighting. Cover plants in late afternoon, before temperatures drop:

• Old bedsheets, drop cloths, or floating row cover. Plastic touching leaves freezes them — if using plastic, support with stakes so it doesn’t touch foliage.
• Anchor edges with rocks, bricks, or stakes — wind blows covers off the moment you go to bed.
• Remove covers in the morning once temperatures are above 5°C. Trapped moisture and heat under covers cause issues if left on through warm days.
• For a single tall plant, a tomato cage with a sheet draped over it works as well as anything fancier.

A cover is good for 2–4 degrees of frost protection. If the forecast calls for -3°C or colder, covers won’t save tomatoes — harvest first.

The final harvest

When hard frost is certain (within 24 hours), pick everything. Don’t leave anything to chance — all the time invested in those plants comes down to this last weekend.

• Red and pink tomatoes: Pick. Eat or process within a few days.
• Mature green tomatoes (full size, glossy, slight white blush at the bottom): Pick. They’ll ripen indoors.
• Small green tomatoes (still hard, dull): Pick the larger ones; small ones won’t ripen and are better for relish or fried green tomatoes.
• Peppers, all colours: Pick. Most won’t change colour indoors but green peppers are perfectly usable.

Pull entire plants up by the roots and hang upside-down indoors as an alternative — the fruit continues drawing energy from the dying plant for several weeks. This produces better-ripened tomatoes than picking individual fruit, but takes more space.

Ripening green tomatoes indoors

Tomatoes ripen via ethylene gas, which they produce naturally. Indoor ripening just lets the process continue:

• Spread tomatoes in a single layer on newspaper, somewhere room-temperature (18–21°C).
• Don’t put them in sunny windows — sun cooks rather than ripens. Diffuse light or shade is fine.
• Add a banana or apple to speed things up — both produce extra ethylene.
• Check daily; ripe ones can spoil others.
• Mature green tomatoes ripen in 2–3 weeks. Smaller ones can take 4–6 weeks or never fully ripen.

Refrigerated tomatoes don’t ripen and lose flavour permanently. Don’t put any in the fridge until they’re fully red.

Using what doesn’t ripen

• Green tomato relish or chutney — the classic Prairie use. Recipes online; jars keep a year.
• Fried green tomatoes — sliced thick, dredged in seasoned cornmeal, fried in oil.
• Green tomato salsa verde — less common than tomatillo but works.
• Green peppers — freeze whole or sliced for winter cooking. Won’t change colour but flavour holds.

End-of-season cleanup

Pull tomato and pepper plants once you’ve harvested. Don’t compost them if you saw any sign of late blight or septoria leaf spot — bag and dispose. Healthy plants can be chopped and added to the compost pile. Leaving frost-killed plants standing through winter spreads disease into next year’s soil.