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Planting and nurturing a new cherry tree can be a rewarding task for gardeners who are willing to put in the time and effort. As winter approaches, it’s a good idea to protect your investment by making a plan to care for your tree throughout the winter.
Cherry trees can survive winter and in fact, require periods of colder weather for dormancy. “Low chill” varieties do best in climates with winter temperatures above 45 degrees Fahrenheit. Others such as tart and sweet cherry trees require a certain number of hours of winter temperatures to thrive.
So cold winters are actually good for cherry trees. With some strategic care on your part, your tree will survive many winters.
Cherry trees are cold-hardy, which is why they are a popular choice for growers in northern zones with low winter temperatures. They even have chilling requirements, known as “chill hours,” which make it necessary for them to spend some time in cold weather in order to be healthy in the spring.
Cherry trees are deciduous fruit trees, which means their growth follows a predictable pattern: they grow rapidly during the spring and summer, slow down in the late summer and fall, and go dormant for the winter. These patterns are governed by the tree’s hormones.
As the days grow colder and shorter in the fall, the tree releases growth inhibitor hormones that keep the tree from producing any new growth. These hormones cause the tree to go dormant; even if temperatures surge back up, the tree won’t grow new shoots or leaves.
This is a built-in form of protection. Warm periods never last long in winter in many climates, so new growth brought on by heat would be killed off as soon as temperatures dropped below freezing. Trees’ growth inhibitors make sure that doesn’t happen.
Trees stop producing growth inhibitors once they have experienced their required number of chill hours, during which temperatures must be between 32℉ and 45℉. Chill hours accumulate throughout the winter, so don’t worry if your winter temperatures fluctuate beyond that range.
Tart cherry trees require approximately 1,200 chill hours (about seven weeks total), and sweet cherries require between 1,100 and 1,300 (six to eight weeks total). Once this requirement is met, the tree will stop releasing growth inhibitors and begin preparing for spring. This is called “breaking dormancy” (source).
Extended periods of mild weather–more than just a few days in a row–can disrupt the chilling process, and make it less effective overall.
When winters aren’t sufficiently cold, cherry trees’ spring growth won’t progress normally. After a mild winter, you may notice one or more of the following:
- Delayed foliation (late leafing out)
- Lengthy blooming period
- Weakened buds
- Flower drop
- Limited flower production
- Limited fruit harvest, or no harvest at all
As disappointing as that sounds, none of those are signs that your tree is dying! Be patient, continue to keep your tree healthy, and hope for colder temperatures next winter.
If you live in a zone that consistently has mild winters, with very few days reaching below 45℉, look for cherry tree cultivars that are considered “low chill.” Usually, these will be ornamental varieties, like Taiwan cherry (Prunus campanulata), which do well even in the coastal regions of the southern U.S. (source).
Note: Cherry trees are one of the best fruit trees to grow in Zone 7b. See our complete list.
Avoiding Winter Injury
While cherry trees do require some cold temperatures, they do not tolerate extremes very well. If you live in a zone that has particularly harsh, long winters, choose a cultivar that is cold-hardy in your zone.
If your climate is usually moderate, but you experience an unusually cold, lengthy winter, your tree may show one or more of the following signs of winter injury:
- Dieback in the upper branches
- “Bruising” or softening of branch tissue
- Dead, brown tissue underneath the tree’s bark
- Overall loss of vigor
Often winter injury occurs when fruit trees have already met their required number of chill hours. Once they break dormancy and lose the protection of their growth inhibitors, they become susceptible to damage from the low temperatures that weren’t a threat previously.
If you notice any signs of winter injury, prune the dead tissue as soon as possible. Dead tissue provides an excellent breeding ground for bacteria and fungi that can spread and infect living tissue.
Unfortunately, there is nothing growers can do to prevent a long, harsh winter. However, there are other controllable factors that influence a tree’s ability to withstand winter injury:
- Avoid over-fertilizing, especially near the end of the growing season. Over-fertilization can cause problems for the tree as it enters dormancy. If the tree isn’t fully dormant before winter, it is likely to show damage in the spring.
- If you live in a dry area, irrigate regularly to prevent drought stress. Trees that are stressed enter fall and winter in a weakened state, which makes them more susceptible to injury as well as disease (source).
Avoiding Injury During Late Spring Freezes
Late spring freezes are extremely frustrating for fruit growers, since they can limit–or completely eliminate–any chance of a harvest.
The extent of damage done by a late spring freeze depends on the stage of the tree’s blooms. In general, when temperatures drop suddenly, the tree is in the most danger if its blooms are already full and open.
When a tart cherry tree’s flowers are in the very first “swollen bud” stage, the tree will lose about 10% of the buds if temperatures reach 15℉ and remain there for thirty minutes. If temperatures reach 0℉ for thirty minutes, the tree will lose 90% of its buds.
However, by the time a tart cherry tree’s flowers are in their final post-bloom stage, they can only withstand temperatures of 28℉ for thirty minutes. When the temperature falls to 25℉, the tree will lose 90% of its blooms.
Sweet cherries are a little bit less cold-hardy. In the swollen bud stage, they will lose 10% of their buds at 17℉ and 90% of their buds at 5℉ (source).
If your tree is small enough, you can protect it from a predicted freeze by covering it with plastic or a row cover. To be effective, you will have to cover your tree completely.
If that isn’t feasible for you, you can still reap a good harvest even if you lose 10% of your blooms. Furthermore, while it would be extremely disappointing to lose 90% of your blooms in a late freeze, you can still keep your tree healthy so it has a chance of being productive next year.
Winter Care for Cherry Trees
You may have heard that you should prune your cherry trees before they go dormant in the fall. This is not a good idea. The wounds left by pruning are more susceptible to winter injury as well as disease.
Instead, prune your cherry trees in the late winter or early spring. There are several reasons for this, including:
- It’s easier for you to identify any winter-damaged limbs or branches.
- Pruning wounds heal more rapidly once the tree begins actively growing.
- The absence of leaves makes it easier for you to see where to make your cuts.
Depending on the size of your tree and your own level of skill, you may wish to avoid injuring yourself by contacting a tree expert or a horticultural specialist to assist you.
All perennial plants, fruit trees included, need less water in the winter when they aren’t actively growing. If you live in an area that receives regular rainfall or snow during the winter, you probably won’t need to water your tree at all.
If you experience an unusually dry winter, you might wish to water occasionally, but check the soil first. If the soil feels dry six inches below the surface, and you don’t expect precipitation, give your tree enough water to keep the roots from drying out (source).
Test your soil and get specific recommendations for addressing deficiencies. Click here to learn more (link to SoilKit by AgriTech).
Cherry Trees in Containers
If you planted a cherry tree in a container, make sure to do the following to keep it healthy throughout the winter:
- Move your tree into an unheated shelter for the winter. Do this gradually to avoid shocking your tree with sudden light and temperature changes. This will protect it from extremes while still ensuring it gets enough chill hours.
- Slowly reacclimate your tree to sunlight in the spring.
- Cover your tree or move it back into an unheated shelter if the forecast predicts a spring freeze.
For more about caring for cherry trees in containers, refer to our article “Growing Cherry Trees in Pots: Keys to Success.”
Not only can cherry trees survive winter, cold temperatures are necessary for them to thrive! You can’t prevent the occasional long, extreme winter, but keeping your tree healthy all year round can limit the damage done in those seasons. Avoid over-fertilization, prune wisely and strategically, and don’t be discouraged by late freezes.