Fruit trees need a certain number of chill hours during winter to produce a bountiful harvest. Chill hours are a measure of how long the temperature is below 45 degrees Fahrenheit (7 degrees Celsius). Unfortunately, winters have become warmer and warmer, negatively impacting fruit tree production.
To increase chill hours for fruit trees, choose varieties that need fewer hours, place trees in areas likely to experience cooler temperatures, or use shading techniques like painting the tree trunk or wrapping the tree. Leaf stripping can also help when done correctly and at the right time.
However, increasing chill hours can be challenging, especially when you lack the knowledge and expertise. In this comprehensive guide, I will explore in detail the top ways you can increase chill hours for fruit trees. Keep reading to find out how you can increase chill hours for fruit trees and enjoy a bountiful harvest.
1. Choose Fruit Tree Varieties That Need Fewer Chill Hours
While you may not have much control over the weather, you can control which fruit tree varieties you plant. Fruit trees have different chill hour requirements for different reasons, with some needing as little as 200 hours while others need up to 1,200 hours.
Choosing a suitable variety is essential to ensuring a bountiful harvest. For example, if you live in an area with mild winters, planting a fruit tree that requires a lot of chill hours is not ideal as it’s unlikely to get the required number of hours.
On the other hand, planting a variety that needs fewer chill hours is more likely to produce a bountiful harvest as it’s more likely to get the required number of chill hours.
Chill hours help fruit trees enter a state of dormancy, which is necessary to produce fruit. During dormancy, the tree’s energy goes into fruit production instead of leaf and stem growth.
If a fruit tree doesn’t get enough chill hours, it may not enter dormancy, which can impact fruit production. For example, a peach tree that doesn’t get enough chill hours may produce smaller peaches with a bitter flavor.
Some examples of fruit trees that need fewer chill hours include:
- Apricots
- Apples
- Figs
- Pears
- Plums
- Pomegranates
Before planting a fruit tree, research the chill hour requirements so you can choose a variety best suited for your area. Ask your local nursery or agricultural extension office for recommendations on which varieties to plant. Ensure you provide the fruit trees proper care and maintenance, such as regular watering, fertilizing, and pruning to produce a bountiful harvest.
2. Plant Trees in Areas That Are More Likely To Experience Cooler Temperatures
Warm temperatures can signal to a fruit tree that it’s time to break dormancy and start growing leaves and stems before the winter is over. This reduces the number of chill hours the tree gets, which can impact overall fruit production. The cold weather can also damage the tree’s flower buds, reducing the amount of fruit it produces.
Planting fruit trees in areas more likely to experience cooler temperatures can help increase chill hours. The ideal temperature for most fruit trees is between 32 and 45 degrees Fahrenheit. Areas with cooler temperatures have excellent airflow, ensuring the fruit tree stays dormant for longer.
Several areas in your yard are more likely to experience cooler temperatures, such as:
- North-facing slopes: Since they don’t receive direct sunlight, north-facing slopes are more likely to be cooler. The slope’s position also lets it cool down quickly in the evening.
- Shady areas: Areas shaded by buildings, trees, or other structures are also more likely to be cooler. The shade provides protection from the hot sun, which can help keep the area cooler.
- Elevated areas: Higher elevations are typically cooler than lower elevations since they’re closer to the atmosphere. The cooler temperatures can help increase the chill hours for fruit trees.
- Near bodies of water: Lakes, ponds, and streams can also help cool the surrounding air, making it an ideal location to plant fruit trees. As the water evaporates, it releases heat, which can help keep the area cooler.
3. Use Shading Techniques To Keep Fruit Trees Cool
Another excellent and relatively easy way to increase chill hours for fruit trees is to use shading techniques. The goal is to keep the warm temperatures off the tree so it doesn’t break dormancy. A few shading techniques you can use include:
- Placing a tarp over the tree: This is a quick and easy way to shade a fruit tree. Simply drape a tarp over the tree, ensuring that it covers the entire tree. You can also use a tarp to create a makeshift tent by propping it up with sticks or poles. The tarp reflects the sun’s rays, which can help keep the tree cooler. Brightly colored tarps are best as they reflect more sunlight.
- Painting the tree trunk: This technique is often used on citrus trees. The tree trunk is painted white, which helps reflect the sun’s rays and keep the tree cooler. This is a handy technique if the tree is in an area that receives direct sunlight. The painting also prevents sunburn, which can damage the tree.
- Building a shade structure: If you have multiple fruit trees, you may want to consider building a shade structure. This can be anything from a simple canopy to a more complex trellis system. The shade structure should be tall enough to cover the entire tree and offer protection from the sun.
- Using shade cloth: Shade cloth is a type of fabric that’s specifically designed to provide protection from the sun. It’s available in various sizes and can be placed over the tree to create shade. Shade cloth is an excellent option if you don’t want to build a permanent shade structure.
4. Leaf Stripping
Leaf stripping is a pruning technique often used to increase chill hours for fruit trees. The goal is to remove the leaves from the tree, which exposes the fruit to cooler temperatures. This helps the tree stay dormant for longer, increasing fruit production.
Stripping the leaves also prevents snow and ice from accumulating on the branches. The accumulated ice creates a mass that can break the branches, damaging or killing the tree. By stripping the tree, the ice falls directly to the ground, which keeps the roots cool.
To strip the leaves from a fruit tree, simply remove them by hand or with a pruning tool for taller trees. Be careful not to damage the branches as you remove the leaves.
- Place your thumb and forefinger on either side of the leaf stem at the base of the branch.
- Gently move your fingers up the stem until the leaf detaches. Avoid applying too much pressure, which can damage the buds.
- Repeat this process until all the leaves have been removed from the tree.
However, it’s important to note that leaf stripping isn’t suitable for all fruit trees. This technique is most effective on deciduous fruit trees, such as apples, pears, and peaches. Leaf stripping can also be used on citrus trees, although it’s not as common.
5. Use Mulch To Keep the Tree Cool
Besides suppressing weeds, improving soil quality, and retaining moisture, mulching can also help keep fruit trees cool. The mulch provides a layer of insulation, which regulates the soil temperature. This is especially beneficial in hot weather, as it can keep the roots cool and prevent the tree from overheating.
Organic mulches, such as wood chips, bark, and leaves, are the best options for fruit trees. These materials break down slowly and add nutrients to the soil as they decompose. You can also spread a layer of inorganic mulches, such as stones and gravel, around the base of the tree. However, these materials don’t improve the soil quality and can cause damage when applied incorrectly.
To use a mulch to keep your fruit tree cool, simply spread a layer around the base of the tree. The thickness of the mulch should be 2-3 inches (5-7.5 cm). Avoid piling the mulch too high, as this can smother the tree. Leave a few inches (cm) of space between the mulch and the tree trunk. Plus, some people may be allergic to mulch dust, which I’ve written about in another guide: Can Inhaling Mulch Dust Make You Sick
You’ll need to replenish the mulch every few months as it breaks down over time. You can also add more mulch during hot weather to help keep the tree cool.
Final Thoughts
Chill hours are an essential factor in fruit production. They help the tree to enter a dormant state, which is essential for flower and fruit development. Unfortunately, many fruit trees don’t get enough chill hours due to the warm climate.
You can increase chill hours by planting tree varieties that require fewer hours, planting the trees in a cool location, or using pruning techniques like leaf stripping. You can also use a mulch to keep the tree cool. By taking these steps, you can ensure that your fruit trees get the chill hours they need to produce a bountiful harvest.
