Trees and shrubs are hardier than most plants but are still susceptible to frost damage. Knowing how to protect trees and shrubs to weather a freeze will ensure they survive the winter. That said, watering them properly can help improve their chances of making it through winter.
You should water trees and shrubs before a freeze as it helps plants stay plump. Watering forms a layer of protection that insulates plants and helps them survive freezing temperatures. Wet soil also stays warmer than dry soil, which protects the roots so they can easily draw necessary nutrients.
This article will explore what a deep freeze means for plants and explains why watering before a deep freeze is helpful. It will also explain how to water before a freeze and other methods to protect your plants when the temperature drops, so read on!
How Watering Before a Freeze Help Your Trees and Shrubs
Watering helps trees and shrubs survive extremely cold temperatures in several ways.
- Prevents and relieves drought stress. Plants that have insufficient water in their cells are said to be drought-stressed. This condition can affect the frost-hardiness of pants and make them more vulnerable to injury during a freeze. Watering ensures that all the plant cells are well-hydrated and flexible rather than brittle and easily damaged.
- Keeps the soil warm. Moist soil is warmer than dry soil, so watering your trees and shrubs provides a little more protection for their roots as the freeze sets in. Well-watered soil can absorb and hold onto heat a lot better, so if you get any sunlight during the day, the wet soil can insulate your trees and shrubs.
- Forms an insulating layer on plant tissue. An old gardener’s trick involves misting the shrubs and trees with extremely cold water at night. As the water freezes over the leaves and trunks, very little heat is released and keeps the ice at a steady temperature. This thin layer of ice protects plant tissue and keeps the water inside the tissue from freezing.
Do’s and Don’ts of Watering Before a Freeze
Here’s how you can water your trees and shrubs before a freeze the right way.
Do
- Water right before a freeze. You’ll want to ensure that the ground is soaked through to about 6-12 inches (15-30 centimeters) deep to keep the roots warm but be careful not to overwhelm the roots. Learn when to stop watering your trees in my article that explains when to stop watering fruit trees: How to Know When to Stop Watering Fruit Trees
- Sprinkle your trees and shrubs the night before. Leave your sprinklers on while the temperatures stay low. The cold water will freeze at a low temperature, releasing little heat and forming a protective barrier over plant tissue. Your sprinklers must be designed for frost protection and rotate evenly to ensure that all the plant tissue is protected by water freezing at low temperatures.
- Continue sprinkling after the freeze. If you’re sprinkling water on your trees and shrubs, you need to continue sprinkling as the temperature rises. Doing so will protect plant tissue and prevent them from dying of shock with the temperature change.
- Add supplemental fertilizers after the freeze. If you’ve used the sprinkling method to protect the tender tissues of your trees and shrubs, the excess water will carry off the nutrients in the soil. Be careful to add only what your plants need. The wrong nutrients can be damaging, as I explain in my article about watering plants with rooting hormones: Can You Water Plants With Rooting Hormone?
Don’t
- Overwater your trees and shrubs. Overwatering is always dangerous, especially before a freeze when the excess water has nowhere to go. The stagnation can lead to diseases and root rot and damage your plant instead of protecting it from the cold.
- Stop watering when the sun comes out. The sun is not an indication of higher temperatures. Continue sprinkling your trees and shrubs until the temperatures rise above freezing .
- Use the wrong kind of sprinklers. If your sprinklers put out too much water at once instead of a gentle mist, sprinkle section by section, or water unevenly, they’re wrong. You need to use sprinklers that are meant to help protect plants from frost. Otherwise, you’ll end up drowning your trees and shrubs in water and distributing the water unevenly, damaging them.
- Use the sprinkler system before a long or very cold freeze. It is very important to ensure that you don’t use the sprinkling method during a long freeze. You’ll end up with too much ice that will kill your trees and shrubs. The sprinkling system is only effective to about 21°F (-6°C). Any lower, and the ice will not stop at being a protective shell but go deeper into plant tissue.
Should You Water After a Hard Freeze?
Watering before a freeze helps protect your trees and shrubs, but watering after a freeze is just as important.
Water after a hard freeze to help thaw out the ground and replenish water in your trees and shrubs. Water will always be warmer than frozen ground, so you don’t need to warm it up first. Just ensure that you apply it evenly across the ground when the sun comes out early in the day.
Watering your plants, trees, and shrubs before and after a hard freeze ensures that they’re sufficiently hydrated for the weather and can survive the winter. As always, avoid overwatering because you risk water stagnation and related issues.
If you notice any leaves or stems with mushy brown or black tips, they’re likely victims of frost damage and overwatering, so you can snip them away. But you don’t need to prune if your leaves are only drooping and wilting.
Give your trees and shrubs time and water to recover from a hard freeze before deciding what needs to be pruned away.
Other Ways To Protect Your Trees and Shrubs Before a Freeze
Watering your plants before a freeze is just one of the ways that you can protect them. Here are a few other methods you can use.
- Cover your shrubs. While you might find it difficult to cover your trees, you can use blankets, plastic, or a tarp to cover your shrubs overnight. The cover will trap the heat rising from the soil and keep your shrubs warm.
- Layer mulch, dried leaves, or lightweight soil on the ground. The soil will be warmer than the ambient air. You can trap the heat in the soil and protect the roots of your plants by layer mulch or dried leaves on top. Light and easy-to-remove soil, like sand, is also a great option. These layers trap water and heat, so your trees and shrubs have a fighting chance against the freeze.
- Add fertilizer before the freeze. A good quality fertilizer will bolster your trees and shrubs and protect them during the freeze. Be careful to use extremely diluted fertilizer, and add less than the recommended quantity to prevent any sudden growth that will damage your trees.
What Is Considered a Deep Freeze for Plants?
Temperatures below 24 °F (-4.4 °C) are considered deep freezes, though a freeze can be generally understood to be temperatures when water freezes at 32 °F (0 °C). Watering before a freeze can help your plants survive a deep freeze when used with other protective measures.
Cold weather brings several challenges for gardeners, including the damage caused by frosts and freezes. Extreme cold can turn the water inside plant tissue into ice, and when the weather gets warmer, the melting of this ice kills the tissue.
If the water in plant tissue turns into ice, that can lead to permanent damage and even death. Evergreen trees and shrubs are more sensitive to damage caused by deep freezes, especially prolonged ones. However, they may develop new growth in spring, so don’t give up hope if you see your evergreens struggling in the winter.
Freeze warnings are typically issued across the country when there is a significant likelihood of the temperatures dropping to 32 °F (0 °C). This is the right time to take action and help your plants by watering them and taking other protective measures, so they survive a deep freeze.
Final Thoughts
You should water your trees and shrubs before a freeze as the water will provide additional insulation. The tissues of well-watered trees and shrubs will also have better resistance to freezing temperatures.
You can also water the surfaces of your trees and shrubs with a steady light misting of water during a cold night. The water will freeze at a low temperature, forming a shell around the plant tissue, thereby protecting it.
