I’ve been researching blueberry plants a lot recently and I was wondering how to properly care for them—reducing the chance they’d lose their leaves and die. So, I dug a little deeper. Here’s what I found about why blueberry bushes lose their leaves and how to prevent it.
Since blueberry bushes are deciduous, they normally drop their leaves in the fall and winter. However, if their leaves are dropping in the spring or summer, it’s likely due to improper watering, nutrients, or temperature. For best results, water when the soil is dry, use quality fertilizer, and plant in zones 4-7.
So, while blueberry bushes drop their leaves for several reasons, how can we tell which issue they have, and from there—how can we treat it? Let’s take a closer look.
Blueberry bushes are deciduous plants, so they naturally lose their leaves in the fall and winter. This is a survival strategy many plants picked up to successfully live in more temperate climates. By shedding their leaves, the plants enter a dormant state—similar to a bear hibernating.
Typically, these plants require chill hours to stay in dormancy (under 45ºF). Warmer blueberry varieties require around 200-300 chill hours, while colder varieties prefer 800+ chill hours (source).
On the other hand, evergreen plants keep their leaves year-round. These plants either developed other ways to survive the cold, or live in tropical climates (with little to no frost).
So, if your blueberry plant is losing its leaves in the fall or winter, know that this is normal. However, what happens if it’s losing leaves in the spring or summer?
Under or Over-Watered
The most common issue blueberry bushes get is improper watering. Generally, under-watered blueberry bushes get leaves that dry, curl, and brown before falling. On the other hand, over-watered blueberry bushes get yellow or brown leaves before falling off. Sometimes the green leaves will also drop.
So, what’s the best method to water blueberry bushes?
The best way to water blueberry bushes is to only water when the soil is dry. A good way to check this is by pushing a finger into the first 2-4 inches of soil. By only watering when dry, you’ll prevent both under and over-watering.
Additionally, provide compost and mulch.
Compost provides plenty of nutrients and improves the soil’s richness—for every 1% increase in the soil’s richness, 1 acre of land can hold an additional 20,000 gallons of water (source).
Mulch (such as leaves, bark, and pine needles) protect the soil and the beneficial soil life from drying out in the sun and wind. As a result, it also prevents topsoil erosion. Mulch is great at reducing evaporation, keeping in available in the soil—hydrating your plants and regulating their soil temperature.
Apply 2 inches of compost every 1-2 months and 4 inches of mulch every 3-6 months. Place these amendments on top of the soil, under the canopy, and at least 3 inches away from the crown (to prevent mold).
However, if your blueberry bushes have poorly draining soil, hold off on the mulch until it’s amended a bit. This is especially common in heavy clay soils.
Potted blueberry bushes with poor drainage can simply be repotted with fresh potting soil.
Planted blueberry bushes are more difficult to amend as digging them up often results in transplant shock (stressing the plants even more). In this case, provide 2 inches of compost every 1-2 months. Over time, the compost will work its way into the soil.
If you haven’t yet planted your blueberry bushes, and you have heavy clay or other poorly draining soils, consider planting in mounds of soil. For more about clay soil and planting in mounds, check out my other post.
Blueberry bushes that are over or under-fertilized can become stressed, leading to brown and dropping leaves. A lack of nutrients causes deficiencies while nutrient potency from excess fertilizer causes the blueberry’s roots to burn. For best results, use a quality fertilizer once a year or compost every 1-2 months.
Chemical Fertilizers vs Compost
While chemical fertilizers have nutrients in quantity, they typically lack nutrients in quality. This can cause stress for the blueberry plants as they’re unable to absorb sufficient nutrients. Additionally, much of the nutrients from chemical fertilizers are often leached from the soil.
Chemical fertilizers can also have other, unintended consequences, such as killing beneficial soil life and drying out the soil.
Fortunately, compost and manure have been found to contain more than sufficient nutrients for plants (which include blueberries).
Approximately 70-80% of nitrogen (N), 60-85% of phosphorus (P), and 80-90% of potassium (K) found in feeds is excreted in the manure. These nutrients can replace fertilizer needed for pasture or crop growth, eliminating the need to purchase fertilizers.University of Massachusetts Amherst
Compost also feeds beneficial soil life such as earthworms and mycorrhizal fungi, leading to benefits such as improved soil aeration, nutrient availability, and disease resistance.
Mycorrhizal fungi promote many aspects of plant life, in particular improved nutrition, better growth, stress tolerance, and disease resistance.Department of Biology, University of Fribourg, Switzerland
However, if you’re not big on compost, you can find out more about the blueberry plant fertilizers that I do recommend on my recommended fertilizer page.
Keep in mind that nutrients aren’t everything—blueberry plants also need a specific soil pH to properly absorb nutrients and thrive.
Blueberry plants prefer a soil pH of 4.5-5.5 (source). This is important because an acidic soil pH dissolves the solid nutrients in the soil, and makes them available to be absorbed by the plant’s finer roots.
Fourteen of the seventeen essential plant nutrients are obtained from the soil. Before a nutrient can be used by plants it must be dissolved in the soil solution. Most minerals and nutrients are more soluble or available in acid soils than in neutral or slightly alkaline soils.Donald Bickelhaupt, SUNY College of Environmental Science and Forestry
Two good ways to check the soil’s pH are with pH strips or a pH meter. I prefer using a meter since they’re affordable and easy to use. To see which pH meter I use and recommend, check out my recommended tools page.
If you do find that your blueberry plant’s soil pH is too acidic (below 4.5), consider adding alkaline materials to the soil like biochar, powdered lime, or wood ash.
On the other hand, if your blueberry plant’s soil pH is too alkaline (above 5.5), use acidic amendments such as sand, peat moss, and coffee grounds.
The majority of blueberry bushes prefer USDA hardiness zones 4-7. Although, some varieties can handle colder or warmer weather. When blueberry bushes either get too hot or too cold, they begin to shed their leaves to ensure the rest of the bush survives. The leaves typically turn brown before they drop.
Once you identify which hardiness zone you’re in, check out this table I put together to show which blueberry varieties do the best in each zone.
|Rabbiteye or Southern Highbush
Now, let’s take a look at what happens to the blueberry bush when the climate either gets too hot or too cold for the blueberry bush (and what you can do to reduce or reverse their falling leaves).
When blueberry bushes get too hot (generally above 85ºF), their leaves dry out quicker than their roots can transport moisture—to cool the leaves. As a result, the leaves begin to dry, curl, brown, and drop.
So, what can you do to protect blueberry bushes from hot weather?
- Provide compost to improve the water retention ability of the soil. This goes a long way in regulating the soil temperature and cooling the plant.
- Apply mulch to further regulate the soil temperature and keep more water in the soil.
- Provide shade for the blueberry plants by using umbrellas, shade sails, or other trees. A good way to do this is by planting blueberry companion plants that are overstories such as pine and oak trees.
Blueberry bushes are deciduous, so it’s normal for them for their leaves to turn yellow, red, brown, and drop in the fall and winter. However, if you have an unusually warm winter, the blueberry bushes might think it’s spring and come out of dormancy and begin growing.
This can be a problem because the new blossom leaf growth on blueberries can be killed if there is a later frost.
But, what happens if the weather gets too cold for blueberries?
The majority of blueberry varieties can survive down to zone 4, which has an average minimum temperature of -20ºF to -30ºF. Any colder than -30ºF, and the blueberry bushes will begin to die.
If you get temperatures under -30ºF, you can protect blueberry bushes by:
- Provide 1 foot of mulch to insulate the roots of planted blueberry bushes and regulate soil temperature (this also works in hot weather)
- Plant blueberries facing the southern sun to maximize the amount of sunlight they receive (this is the northern sun if you live in the southern hemisphere)
- Avoid bringing potted blueberry bushes indoors as they require chill hours to fruit (temperatures 45ºF and below)
So, if your blueberry plant is losing leaves in the fall or winter, you generally don’t need to worry about it. However, if it’s losing leaves in the spring or summer, check its watering, nutrients, and weather. Chances are that one of these factors is stressing the plant out.
If you find that none of the above causes explain why your blueberry plant is dropping its leaves, two other reasons blueberry bushes are from pests and diseases.
You can tell if a blueberry bush has pests by inspecting the leaves and the berries. You should be able to see the pests themselves or signs of the pest such as holes in the leaves or fruits. To see more about pests and how you can treat blueberry plants of them, check out this resource by the University of Maryland.
On the other hand, diseases are typically shown as yellow, red, or brown spots or blotches on the leaves and other parts of the bush. To see more about which diseases blueberry bushes get and how to treat them, visit this resource by Michigan State University.