One of my family members in Minnesota is looking at growing cherry trees and was wondering if they would survive the cold northern winters (sometimes hitting below -30ºF). To help them out, I did some research on cherry trees and their hardiness. Here’s what I found.
Cherry trees can survive temperatures as cold as -30ºF to -40ºF, not accounting for wind chill. This includes USDA hardiness zones 3-4. Typically, cherry trees prefer some cold and require a certain amount of chill hours to grow properly. However, the exact cold tolerance depends on the variety of the cherry tree.
So, while cherry trees are impressively cold tolerant and will survive most winters, how many chill hours do they need, and how can you protect them from extremely cold temperatures? Let’s take a closer look.
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Do Cherry Trees Need Chill Hours?
Generally, cherry trees need 1200 hours, or 7 weeks of chill hours in the cold season. Chill hours are consecutive hours with temperatures under 45ºF. Without the right amount of chill hours, cherry trees will have issues developing leaves, flowers, and fruit. The amount of hours required depends on the variety.
|Sweet Cherry Chill Hours||Sour Cherry Chill Hours|
|1100-1300 hours||1200 hours|
|6-8 weeks||7 weeks|
If cherry trees don’t have the appropriate amount of consecutive chill hours, they’ll “wake up” from their dormancy (also called “breaking dormancy”) and will expend energy trying to survive throughout the winter. As a result, they’ll either die or have far less energy in the spring, leading to growth and fruiting issues.
You can think of tree dormancy similarly to how bears hibernate during the winter—they store nutrients during the growing seasons and sleep during the winter, expending little energy. This helps them survive when the water and nutrients are frozen in the soil.
So, what exactly happens if cherry trees are “woken up” from their winter dormancy or don’t get the right amount of chill hours?
What Happens if Cherry Trees Don’t Get Chill Hours?
- Bud drop
- Flower drop
- Reduced flowers
- Extended blooming period
- Delayed foliage growth
- Little to no fruit
If you see any of the above occurring to your cherry tree, don’t worry! These are not signs of a dying cherry tree. Given another season, your cherry tree should recover nicely and continue fruiting. In fact, they’ll likely get a bumper crop the following year after skipping a year of regular growth.
While it can be tricky to figure out how many chill hours your region has, a quick Google search should provide a good baseline for you. For example, California’s chill hours vary dramatically depending on if you’re in the north or south.
Most of Northern California receives between 800 and 1,500 hours of vernalization each winter. Southern California may only receive 100–400 hours.The University of California, Division of Agriculture and Natural Resources
How to Identify Winter Injury on Cherry Trees
Cherry trees get winter injury when exposed to the extreme cold (below -20ºF) for more than 1-2 weeks consecutively. Typically, this results in dieback in the upper branches, bruising of the branch tissue, and overall loss of vigor. While cherry trees can survive this weather, they’ll be stunted the following year.
Generally, cherry trees will likely survive when exposed to the extreme cold for 1-2 weeks, but anything more and they’ll lose their buds and won’t crop the following season. Other issues such as softening branch tissue and loss of energy can also occur.
What’s even worse is if the cherry tree has its dormancy broken and it started developing buds during the winter. If these buds are exposed to the cold, they’ll become damaged and fall off. While some bud loss is normal, excessively cold temperatures will cause most or all buds to drop.
|Sweet Cherry Trees Blooming Stage||Temperature for 10% Bud Loss||Temperature for 90% Bud Loss|
|Swollen Bud (First Swell)||17ºF||5ºF|
|Bud Burst (Green Tip)||25ºF||14ºF|
|White Bud (First White, Popcorn)||27ºF||24ºF|
|Sour Cherry Trees Blooming Stage||Temperature for 10% Bud Loss||Temperature for 90% Bud Loss|
|Swollen Bud (First Swell)||15ºF||0ºF|
|Bud Burst (Green Tip)||26ºF||22ºF|
|White Bud (First White, Popcorn)||28ºF||24ºF|
If your cherry tree does lose most of its buds in the winter, the tree will still likely survive. There will just be little to no blossoms and fruit the following season. Again, all is not lost—there’s a good chance your cherry tree will have a bumper crop the next year.
Generally, if your climate gets colder than what your variety of cherry tree can handle, setting up some protections can go a long way (especially if you see extreme weather on its way).
How To Protect Cherry Trees in the Winter
Planted Cherry Trees
- Mulch the base
- Wrap or cover the tree
It’s important to water your cherry tree just before the first frost. This will help keep the soil moist, and not wet or dry when the soil freezes.
Typically, watering cherry trees throughout the winter isn’t necessary unless the soil gets extremely dry. If you’d like to check for this at any point during the winter, feel the first 2-4 inches of the cherry tree’s soil for moistness. For more about watering in the winter, check out this guide by the University of Arizona.
Mulching the base of your cherry tree will provide a great deal of insulation and prevents the snow and ice from touching the tree directly. Some good mulches for cherry trees are leaves, bark, grass clippings, pine needles, and straw. Keep in mind that mulch will become compacted over the winter weather, so stack it about 20% higher than normal.
If the weather is extreme enough (especially under -30ºF) wrapping or covering your cherry tree with cardboard, bedsheets, or plastic tarps are incredibly effective. If you get a lot of wet snow and ice, the plastic tarps in particular will go a long way as they’re generally water-resistant.
Pro-tip: Snow is a fantastic insulator and will be sufficient cover for most cherry trees in mild to moderate winters.
Potted Cherry Trees
While it might seem like potted cherry trees can be simply brought indoors during the winter, this can often cause more harm.
As mentioned above, cherry trees require chill hours, and moving them indoors will often expose them to temperatures above 45ºF (even if they’re simply in your basement). This will likely break their dormancy and negatively affect their growth cycle, leading to reduced foliage, flowers, and fruit.
So, once you find a good spot to keep your potted cherry tree, what are some ways you can winterize the tree and protect it from the extreme cold?
- Insulate the pot
- Wrap or cover the tree
Like planted cherry trees, watering potted cherry trees before they go dormant will help keep the soil moist and prevent the tree’s roots from drying out or icing over.
Insulating potted cherry trees is a bit different than planted cherry trees. Planted cherry trees have lots of soil to help insulate the base of the trunk and its roots. Because of this, you might need to help out potted cherry trees a bit with some material.
For example, a common method to insulate potted cherry trees is to either bury the pot or put it into a box. You can then cover the top of the buried pot or fill in the gaps of the box with dirt or mulch. Leaves and straw are great insulators to add to the box. Remember to add at least 20% more mulch and ground cover as it will compress over the winter.
If temperatures get extremely cold, consider wrapping and/or covering the tree with bubble wrap, cardboard, or a plastic tarp. Any insulation is better than nothing, and even a thin sheet of plastic happens to be an amazing insulator (this is why they make emergency blankets out of plastic and reflective material).
If you do move your potted cherry indoors, avoid placing it in an area with central heat. Other than not getting the appropriate amount of chill hours, the heat will quickly dry and kill the plant. This actually started to happen with my potted Meyer lemon tree (see image below).
Cold-Hardy Cherry Tree Varieties
|Cold-Hardy Cherry Trees||Hardiness Zone|
|Canada Red Select (Sour)||2-7|
|Carmine Jewel (Sour)||3-8|
|Evans Bali (Sour)||3-9|
If you don’t have a cold-hardy cherry tree yet, or if you’d like to check your current cherry tree variety, feel free to refer to the above table I put together.
Generally, sour cherry trees are hardier than sweet varieties due to their late flowering and reduced root dieback. However, there are some sweet cherry varieties such as Juliet cherries that have been hybridized with sour cherry varieties.
Keep in mind that even if you get a cold-hardy cherry tree, conditions such as soil, sun, wind, water, and humidity play factors in how cold it is in your region.
Because of this, you can place a thermometer in the location of your future cherry tree to get a more accurate temperature reading. Remember to factor in for the occasional, unusually cold winter.
More Tips To Care for Cherry Trees in the Winter
- Avoid fertilizing in the winter. Since cherry trees are dormant in the winter, they won’t need extra nutrients in the soil. Some chemical fertilizers (especially fast-release fertilizers) can even burn the tree’s roots during the winter, leading to root dieback and sometimes killing the tree.
- Water your cherry tree once right before the first frost. While in dormancy, cherry trees don’t need additional water, light, or fertilizer. Typically, the tree won’t need anything else other than protection from temperatures under -30ºF.
- Use hardware cloth to keep hungry mice and voles from gnawing at your cherry tree’s trunk during the winter (especially if the tree is outside and buried in leaves).
- Cherry trees are more susceptible to the cold depending on their growth stage. For example, open flower buds are more susceptible than closed buds. Similarly, younger fruit is more sensitive than flowers in full bloom.
- When moving potted cherry trees to a shelter, do it gradually over 2 weeks. Cherry trees can get stressed from sudden temperature and light changes, which weakens the tree. The same goes when acclimating the tree back to the outdoors in the spring.
- Place multiple potted fruit trees close together to increase warmth. If you have more than one potted cherry or fruit tree, huddling them together will increase their temperature slightly and help protect them from wind chill.
- Avoid pruning in the winter as this can wound the tree, making it difficult to heal while the tree is dormant. This can easily open the tree up for infection. Instead, prune after the last frost or in the early spring.
If your cherry tree’s health is declining, and you’re not sure why, feel free to check out my recent post: 3 Quick Steps To Revive a Dying Cherry Tree.