How To Protect Your Plants from the Cold

For everything, there is a season, and when it comes to gardening, there’s a season where you need to stay vigilant about keeping your plants warm. If you want to extend your fall season crops or get a head start on your spring season crops, it’s even more important to be aware of when temperatures will drop. You’ll want to make sure you protect your plants from the cold.

How To Protect Your Plants from the Cold One of the great things about living in Florida is that you can grow warm season crops during fall and winter. But we have to stay aware of our cold snaps. Whether you live in a warmer climate like Florida, or somewhere else with cooler winters, it’s important to know how to protect your plants from the cold.

Is it as simple as throwing an extra bed sheet over your plants when the weather person forecasts 32°F?

Not exactly.

There’s a couple of factors – The temperature (along with a few other weather elements) and plant hardiness. We’ll go over each of these and then see how to protect your plants from the cold.

Temperature – Frost vs Freeze

Frost – Frost can actually occur when the air temperature is at 37°F or below. That’s the temperature you see on your weather app. Ground temperature is different from air temperature, and can actually be colder than air temperature. When the ground temperature is  32°F and water vapor freezes on the ground you get tiny ice crystals that create frost. Usually, this occurs when it’s a calm, clear night and heat radiates up from the ground. Clouds can absorb and reflect heat back to the earth, preventing a frost. Wind can also prevent air from settling, preventing a frost.

Some plants can be damaged by frost. So even though the weather forecaster isn’t predicting a freeze, once temperatures start to drop below 40°F you need to be aware. Once temperatures drop below 40°F, you may want to start covering your plants with a frost blanket depending on what you’re growing, which we’ll get into in just a bit.

Freeze – A freeze is when the air temperature is 32°F or below. Just because there’s a freeze doesn’t mean there will also be a frost.  Though, to ensure you’re confused, a dry freeze is sometimes referred to as black frost. 🙂 Freezing temperatures can create ice crystals in your plant’s cells. The ice expands and then bursts the cell walls causing damage to your plants, and potentially killing them.

  • Light Freeze occurs when temperatures drop between 28-32°F
  • Hard Freeze occurs when temperatures fall below 28°F
  • Severe Freeze occurs when temperatures fall below 25°F

In addition to how cold it gets, how long it remains at that temperature is also a factor to take into account. The soil loses the warmth it has the longer it stays cold.

Plant Hardiness

Some plants are more tolerant to cold temperatures. By making sure you choose varieties of vegetables that are right for your growing zone and choosing the right plants for the season, you’re already proactively preparing for cold snaps.

Cold-Sensitive Plants
(Below 37°F)
Light Freeze Tolerant Plants
(28-32°F)
Hard Freeze Tolerant Plants
(Below 28°F)
TomatoesLettuceKale
PeppersChinese CabbageCollards
EggplantPeasSpinach
Summer SquashCeleryBroccoli
Winter SquashSwiss ChardBrussels Sprouts
PumpkinCauliflowerCabbage
MelonsCarrotsMustard Greens
CucumbersParsnipRadishes
BeansBeetsOnions
Sweet PotatoesEndiveTurnips
OkraEscaroleKohlrabi
BasilPotatoesRutabaga

While flowering, warm-season vegetables (like peppers and cucumbers) are easily damaged by cold weather, cool-season vegetables (like leaf and root vegetables) are more resilient to hard freezes. When temperatures cool, cool-season vegetables produce more sugar. Sugar water freezes at a lower temperature than water. This keeps the water in the cells from freezing and bursting the cell walls. In addition, these plants have cell membranes that are able to expand more from the ice that forms, which prevents bursting through the cell walls.

One great thing about cold snaps (besides fewer pests!) is that cool-season vegetables end up tasting better. This is because the cold weather makes the vegetables produce more sugar.

Cold-hardiness also varies between varieties. For example – some varieties of cabbage can handle colder temperatures than others. Just like some tomatoes can handle warmer temperatures than others. In addition, Shorter and more mature plants can handle cold weather better.

While the focus in this post is for vegetables, make sure you’re aware of what else you have growing. Tropical plants, house plants, citrus trees, tender bulbs, annuals, and spring blooming shrubs should also be protected from the cold.

10 Tips to Protect Your Plants from the Cold

OK, so we have a better understanding of different temperatures, and what different varieties of plants can handle. So what can we do about it? How can we protect our plants from the cold? Keep reading to find out a few tips:

1. Watch your weather forecast

I signed up for my counties weather alerts during Hurricane Irma, so I actually get texts now if there’s a freeze warning. Whatever your method is – TV, App, Computer – start watching when you get close to your cool weather transition based on your planting zone.

Here’s a quick guide that shows when the average first and last freeze dates are for your planting zone. Here in Central Florida, I’m in Zone 9b.

First and Last Frost Dates Averages by Hardiness Zone

USDA Hardiness ZoneAverage First Frost DateAverage Last Frost Date
1Aug 1Jun 15
2Aug 30Jun 15
3Sep 15Jun 15
4Oct 1Jun 1
5Oct 15May 15
6Nov 1May 1
7Nov 15Apr 15
8Dec 1Apr 1
9Dec 15Mar 1
10Dec 15Feb 1
11-13No FrostNo Frost

**Please note – these are average dates. I’ve experienced freezes in my zone before the average December 15th date. It’s important to be aware of weather forecasts as you get closer to your average first freeze date. This is more of a guide to help you plan when to plant your vegetables.

2. Harvest what you can

If you have any fruiting plants that have started to ripen, you can prevent frost damage by harvesting before it occurs. If I have tomatoes that have started to change colors right before a frost or freeze I will harvest them and leave them on my counter to finish ripening.

3. Bring in what you can

If you have potted porch plants, such as succulents, and the containers are fairly small, you might want to bring those guys in for the night.

4. Water your plants

The ground absorbs heat during the day and gives off warmth to plants at night. If temperatures are going to drop below 40, you can help increase the soil warmth by watering your plants early in the day before the temperature drops. This will help insulate your plants. The moisture in the soil will absorb more heat during the day, and then release it at night to keep your plants warm.

5. Use a ground cover

If you want you can cover the ground with 2-3 inches of a ground cover, like wood chips or straw. This can help to keep your plants warm.

6. Use raised beds

While I wouldn’t recommend going out a building a raised bed the day before a frost, it is something to keep in mind when planning your garden, especially if you live in a colder area. Using raised beds to help guard against cold temperatures because cooler air collects in lower areas. A raised bed acts as a mound. It also helps when you cover your plants because you can keep the edges of your covers lower than your planting surface, creating less chance of wind.

7. Cover Your Plants

This is a must! Even if you use other methods to keep your plants warm if temperatures drop you want to help keep that warmth in by using protection!

Use sheets or blankets. I recommend getting a dedicated frost blanket. These are a low-cost alternative to having your plants freeze. They’re a little thicker than bed sheets, but not so heavy that they’ll crush your plants. The Planket is a green material that is thicker than the shade clothes I use during the summer. There’s a lot of different frost blanket sizes on Amazon, and even some specifically designed to cover trees and pots.

A warning about plastic coverings – they can cause damage. They don’t insulate plants well and it will freeze whatever part of your plant touches the plastic. If you have to use plastic, make sure it doesn’t touch your plants.

8. When to cover

You’ll want to cover your plants mid to late afternoon before your scheduled frost or freeze. Don’t wait until after the sun goes down. Besides the fact that your fingers and toes will thank you later, the purpose of covering your plants is to hold in the heat. If you wait for the temperatures to drop, you won’t be holding in as much heat.

9. How to cover

Make sure your covers go down to the ground. If you have open spots, wind can get in and blow the warm air away. And if there is wind, you’ll want to weigh down your frost blanket with bricks or pots, or whatever else you have on hand. You may also want to use some stakes to hold up your cover so that it doesn’t crush any tender plants beneath it.

10. When to uncover

You’ll want to uncover your plants the next day once temperatures rise to avoid overheating your vegetables and letting the soil warm up again. With shorter days during the winter, plants need all the sun they can get.

You’ll also want to let your covers dry before you fold them and put them away for the next cold snap.

Hopefully, you learned some new tricks on how to protect your plants from the cold. Comment below if there are any specific tricks or tips you use to keep your plants warm!

How To Protect Your Plants from the Cold

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