QUESTION: What temperature is the frost point for plants? Is it exactly the freezing point of water — 32 — or is it higher or lower than that? When should I be worried when I’m looking at my weather app? – Lafina C
ANSWER: Different plants have a different tolerance for frost. In general, the frost point for plants is around 28-degrees Fahrenheit.
More tender plants can be damaged or killed by temperatures ranging from 29- to 32-degrees Fahrenheit.
Plants that are a little sturdier in cooler weather can be damaged in temperatures from 25- to 28-degrees Fahrenheit.
When the temperatures drop below 25-degrees Fahrenheit, even your cold-hardy crops will suffer damage to their foliage and fruits.
When you know frost is arriving, what can you do to protect your crops? Thankfully, there are quite a few steps you can take to keep your plants safe.
The first thing you should do is water your plants. You might think this is counterintuitive, but it isn’t.
Water is a great insulator. Therefore, moist soil and plant cells that are full of moisture will be better protected than dry plants and soil.
The next step you should take is mulch the roots of your plants. This is especially useful for cold-hardy plants. They may not need much more assistance beyond this, but it can make all the difference when they face a hard frost.
Another option is to cover your plants. There are many options within this one solution. You can use anything from row covers, sheets, blankets, or an overturned flower pot or bucket.
Any of these options will help keep frost off your plants. If you have a portable greenhouse, you could even set it up over smaller garden areas or move container-grown plants inside the greenhouse.
The main thing to consider when covering your plants is if you use anything plastic (such as plastic sheeting) to protect them, don’t let the plastic touch your plants’ foliage or fruits.
Cold will transfer through the plastic and can cause severe damage to your plant even though it’s covered.
Another option, if you have the ability, you could plug up electric fans outdoors. Allow the fans to blow over your plants.
This keeps the cold air circulating so it can’t land on your plants and stay there. This will keep them from suffering severe frost damage.
Your final options are for potted plants. These plants have less insulation as their roots aren’t surrounded by as much soil.
Therefore, if you have a greenhouse, move your plants to this location. If you don’t have a greenhouse, move your plants into a basement, garage, or another space inside your home.
You now have an idea of what temperatures will impact each of your plants. You also have multiple solutions to protect your plants from frost.
The best way to avoid frost is to plant after your final frost date in spring or before the first frost of fall.
However, the weather can be unpredictable at times. Plus, there are some areas which have shorter growing periods. This might require different gardening techniques to extend your growing season.
Whatever the reason, when frost is on your radar, be sure to take action and protect your plants using the methods provided.
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