How to save your garden tomatoes after a fall frost

If you have a garden, then every day into September that you stay above zero is a good day. Some of our plants still have food to grow and the days are getting shorter, and cooler.

Save your tomatoes after a frost. Colourful garden tomatoes. Photo copyright Sheri Landry

Then there comes the one day that it’s just done. And that is the day that you wake up to an icy dust-like blanket covering your yard.

Frost. To gardeners, that’s the real f-word.

Sometimes you have warning and you can protect your garden. Sometimes it just got cooler than expected and you are left standing there, staring at the last few month’s hard work you put in and watching as your tomato plants die in front of you.

Depending on how cold and severe the frost was, you may still be able to save your tomatoes.

How frost kills tomato plants

In a nutshell when the temperature drops too low the cells in the tomato freeze. But that isn’t completely what kills your harvest. It’s also the rate at which it thaws. After the freezing has happened, the sun rises, and the quick rise in temperature, even by only a few degrees, causes the cells to die. Both of these happening together is what makes avid gardeners rage when unexpected frost occurs.

How to save your tomatoes after frost

I really didn’t see the frost coming last year. It was really early in September and the day before was warm and I don’t recall any warning of frost. We were supposed to get close to freezing, but that was about it.

I woke up early the next morning to frost everywhere. In a panic I ran outside to see my 14 tomato plants lightly covered with frost. I can’t remember why I was up early (probably letting our cat in), but the sun hadn’t come up yet and I could still see my breath.

Armed with nothing more than the knowledge that frost kills in two steps, I realized that I needed to act quick before the sun came up and the frost started to disappear. I turned on our garden sprinkler and watered the tomatoes with the cold water to attempt to bring their temperature up at a slower rate than it would climb naturally.

Since this was my first time trying this out, I left the water running until one hour after the sun was in the sky. I thought if I could bring the temperature up to the place it would be after I watered them with cold water, then the freezing in the cells should have passed, and then they could warm up with the sun like they normally do after I watered them in the morning.

In the end, it worked. I lost the tomatoes on one side of one plant where the water couldn’t reach. But we saved tomatoes on 13 1/2 plants. And they were delicious.

Keep in mind

This may not happen in every situation. If the frost has passed and is no longer on your tomatoes, their temperature may already have risen and killed the cells. If the frost or the temperature was too severe, there may be no saving them. But for an average frost, if you can get to them at the right time, this should work.

If you like to know the science behind the article, this is a great link about frost damage in plants


Found in Fall, Gardening, House & Home