Frost Protection For Plants: You CAN Make a Difference

Providing frost protection for your plants may be necessary if you want to maximize your growing season.

It doesn't matter whether you’re trying to start early or finish late.

If you know how to protect your plants from frost, you might be able to add a bit of precious time to your gardening season. 

And of course, Mother Nature doesn't always conform to our neatly planned schedule for her.

So you might need to provide frost protection later or earlier than you’d normally expect.

Plenty of Frost-Fighting Weapons Are Available

Fortunately, you have a number of weapons available to you for battling Jack Frost. In fact, if your battle turns out to be only a brief skirmish, your chances of victory are great.

But your weapons won’t work miracles. If Mr. Frost digs in for an extended siege, you may lose the battle.

But better to fight and lose, than to surrender without a struggle! 

What Causes Frost Damage?

Everyone knows that frost can kill or damage plants.

But why?

Frost damage – or freeze damage, since plants can be damaged without frost appearing – occurs when the water within plant cells freezes. The resulting ice crystals puncture the cell walls, destroying the structural integrity of the foliage.

That’s why frost damaged foliage wilts just as if it had been deprived of water.

A number of variables influence the degree of damage, such as the length of time below freezing, how quickly the temperature falls, and how low the temperature falls.

The amount of damage also depends upon the susceptibility of the plant to cold temperatures. Some species are more tolerant of cold than others.

And the stage of growth is also a factor. Young foliage is generally more susceptible to freeze damage than older foliage. 

Your Weapons...

The enemy approaches!

Advance intelligence reports (or to put it more dully: the weather forecasts) indicate a strong likelihood of an attack by the enemy tonight.

So it’s time to prepare for battle!

Your choice of weapons for providing frost protection for your plants will depend upon the circumstances. But most of the proven, effective weapons protect plants from frost by either trapping heat around the plants, or by creating heat.

A very formidable defense would combine both types of weapons.

So let’s consider your options. 

Prevent Frost Damage by Conserving Heat

The easiest form of frost protection is to just make the most of the heat already stored in the ground by retaining some around the plant.

Obviously, that won’t provide you with as much of a defense as supplying extra heat.

But when your battle with Jack Frost is relatively brief and benign, these methods may provide you with all of the frost protection you need: 

Floating Row Covers

Floating row covers – sometimes just called row covers – are used for a number of purposes in addition to frost protection.

They are made from synthetic fabrics such as polyester, and are so lightweight that they can ‘float’ directly on most plants without causing damage.

Often, though, floating row covers are installed with hoops holding the fabric off the foliage.

And if you’re installing row cover over a plant with a fragile growing point, such as tomatoes, you must be certain that the cover is held off the plant. Otherwise, even the very lightweight fabrics may do damage when blown by the wind.

Row covers vary in thickness and material, and both are factors in how much frost protection the row cover offers.

Any row cover you’re considering buying will probably be labeled with the amount of frost protection it offers, but 2 to 4 degrees is common.

Since floating row covers allow light and water to pass through, they can be left in place for days or even weeks at a time. So if you want to set up the row cover just as soon as you plant your seedlings in the spring, and then leave it in place until the threat of frost is past, that’ll work.

(Note: There are some heavier row covers manufactured expressly for frost protection. These are generally too heavy to leave on the plants long term, and should be removed after the frost event has ended.) 

Frost Blankets

Frost blankets are very similar to floating row covers, both in concept and materials. In fact, the terms are sometimes used interchangeably.

But generally, a frost blanket is heavier, and sized to cover large individual plants such as shrubs and small trees.

The heaviest frost blankets are claimed to provide up to 8 degrees of protection. 

Planket

Essentially the same as frost blankets.

The planket is used mainly to cover larger plants. Its advantage is that it comes with a drawstring that is threaded through grommets, making it very convenient and easy to install and remove.

Plankets are particularly great for using with large potted plants.  

Miscellaneous Household Items

Anything that you can use to cover your plants will help to hold in some of the heat escaping from the ground.

Though they likely won’t be quite as effective as some of the items mentioned above, things like bed sheets, towels, and even newspapers can help.

Containers inverted over young seedlings can also provide some frost protection.

Milk cartons, flowerpots, jars, plastic storage containers – anything that will fit over the plant and form a seal with the ground. Even an old cardboard box overturned over a plant is better than nothing.

Sheets of plastic or bubble-wrap can also provide some protection.

If you’re using a non-rigid covering, try to assemble some sort of framework to keep the covering from touching the plant. 

Take Advantage of the Ground's Ability to Store Heat

Whatever method you use to retain heat around your plants, making sure that your garden is well watered during the day will help.

Moist soil will accumulate and hold heat better during the day, and release the heat during the night.

That's particularly true when the day preceding a frosty night is sunny - which is very often the case.

You Can Also Prevent Frost Damage by Creating Heat

Years ago, I was involved in helping my Dad manage his commercial peach orchard.

One early spring day, we received reports that the enemy was nigh upon us.

So we spent the day hauling old tires from a tire graveyard, and stacking them strategically around the orchard. We must have hauled well over 100 tires.

There was no sleeping that night.

We had to stand guard, alert for the approach of the enemy. In the wee hours of the morning, the enemy arrived. He lowered the temperature to 33 degrees on our thermometers.

The battle was on!

One of us manned the gas can, and the other the matches. We made the rounds to each defensive position strategically located throughout the orchard. A slosh of gas, the toss of a match, and – whoomph! A tire was lit.

And those tires REALLY put out some heat!

Throughout the night, we continued to make the rounds of the orchard. Anytime a tire was close to burning out, we’d grab another from the stack of ammunition, and toss it on the nearly burnt out tire.

The battle raged until sunup.

It was a dirty, filthy job from beginning to end. Those old tires were nasty dirty, and splashed swampy, smelly water on us as we hauled them to and from the truck. In the aftermath, cleaning up the ashes of the burnt tires was considerably less than pleasant as well. And burning old tires isn’t exactly an ecologically friendly thing to do. I’d never do it again.

But…it worked.

The temperature fell into the mid 20’s that night. And peach blossoms are very cold sensitive; our crop would have been completely wiped out. Instead, we only had very minor damage in some of the fringe areas.

Of course, I’m not recommending that you set your backyard garden alight with old tires!

But there are some far less harrowing ways of introducing a bit of extra heat into your garden on a frosty night. Let’s examine a few of them: 

Wall O’ Water

The venerable wall o’ water is a great way to protect your small seedlings.

It works in 2 ways.

  1. First, the water in the wall o’ water absorbs heat during the daytime. At night, the water releases the built-up heat, warming the air around the seedling in the process. The insulating property of water helps to hold the heat around the seedling.
  2. If the cold spell is severe enough to freeze the water, additional heat is released as the water changes from a liquid to a solid.

The wall o’ water also provides an excellent shelter against desiccating winds.

You can get some of the same benefit by surrounding your seedlings with plastic bottles of water – things like milk jugs and plastic soft drink bottles. But they won’t work quite as well, or provide quite the protection as a wall o’ water completely enclosing the plant.

A wall o’ water may provide as much as 15 degrees of frost protection under certain conditions – enough to really push the envelope for how early you can set out your seedlings.

Just remember, though, that nothing short of a structure like a greenhouse or cold frame will protect your seedlings during an extended cold snap. 

Sprinklers

Another way to use water to provide heat is by running a sprinkler. You can apply water directly to plants, or for large plants like trees and shrubs, apply water on the ground underneath the foliage.

While using a sprinkler can be effective, this method of frost protection comes with its own set of dangers.

When the temperature drops below freezing, ice will begin to form on the foliage (and though it seems counter-intuitive, the foliage will not be harmed by the ice). The longer the sprinkler runs, the thicker the ice will become. The foliage under the ice will be protected because the constantly freezing water releases heat, some of which is absorbed by the foliage.

But if you turn the water off before the air temperature has warmed enough to melt the ice, your plants will be damaged.

You must let the water run until the temperature has warmed and ALL of the ice has melted. So you might find yourself having to choose between having your plants damaged from the cold, or from the weight of the ice.

And if you need to provide frost protection for several nights in a row, you could end up damaging your plants by waterlogging the soil.

The sprinkler method can be very effective, providing as much as 10 degrees of frost protection. But this method of protection must be used with caution. 

Light Bulbs

You can provide some heat to your plants by using 100 watt light bulbs. Of course, don’t even consider this unless you’re using proper electrical outlets and suitably rated extension cords.

It’s particularly effective to use light bulbs under a covering of some sort, such as floating row covers.

When positioning the light bulb, place it low, underneath most of the foliage. That way, heat from the bulb will rise up through the foliage.

And be sure to position the bulb so that it doesn’t contact the plant directly.

A festive way to use light bulbs is to apply strands of Christmas tree lights to the plant. Threading Christmas tree lights throughout a small tree is a great way to help protect it. Might help to add some cheer to a tense situation, too!

If you do use Christmas tree lights, make sure that you’re using the incandescent lights. The newer LED lights emit very little heat, and will be essentially useless for this purpose.

If you’re not sure which type you have, plug in a strand of lights, and hold your hand close to a bulb. If you can’t feel any heat radiating from the bulb, neither will your plants.

What if Your Plants are Damaged in Spite of Your Efforts?

First – take heart!

Unless the enemy won a total victory, and your plants are dead, then your efforts weren’t for naught. You’ve likely reduced the damage that would have occurred without your intervention. And it might even be that you’ve saved the lives of your plants.

But of course, it’s necessary to access whatever damage has occurred, and decide upon a course of action.

The first thing to do is wait.

Though your plants may look bad, give them a few days to see if they show any sign of recovery. If they begin to put on new growth, then obviously they’ve survived. You’ll just have to decide whether the damage is extensive enough that you’d be better off starting over with new plants. 

Who Says You Can’t Fight Mother Nature?

Part of the joy of gardening is in experiencing a closeness with nature.

And no doubt, part of being a successful gardener is learning to work in partnership with nature. But just as all successful partnerships have their moments of disagreement, there are times when we gardeners find ourselves opposing nature.

So you might think of your efforts at providing frost protection for your plants as nothing more than a brief argument with your partner, Mother Nature. You may win the argument, or lose it.

But at least you’ll have the satisfaction of knowing that you didn’t meekly let your partner walk all over you! 

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