Blueberry bushes have been on my wishlist of plants for a while now, but I’ve heard that a common issue growers run into is brown leaves. So, I did some research to find out why blueberry plants get brown leaves and how to fix it. Here’s what I found.
Blueberry bushes most commonly get brown leaves due to under-watering and extreme weather, but over-fertilizing and some pests and diseases can also cause it. For best results, water blueberry bushes only when the soil is dry and provide quality fertilizer or compost.
So, while blueberry bushes get brown leaves from a variety of different causes, which are the most likely, and how can we fix them? Let’s take a closer look.
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The most common reason why blueberry plants get brown leaves is from under-watering. When blueberry plants don’t get enough water, their leaves begin to dry, curl, and brown in the process. Eventually, without water, the blueberry bush will die.
So, what’s the best way to water blueberry plants?
Ideally, only water blueberry plants when their soil is dry. You can check this by pushing a finger 2-4 inches into the soil. By watering in this way, you’re preventing both under-watering and over-watering. Additionally, provide 2 inches of compost and 4 inches of mulch to retain moisture and protect the soil.
Providing compost and mulch are essential practices that go a long way.
Compost provides valuable nutrients for the blueberry plant (as well as beneficial soil life) and increases the richness of the soil. For every 1% increase in the soil’s richness, 1 acre of soil can hold an additional 20,000 gallons of water (source).
Mulch is equally as important as compost as it protects the soil from drying out and eroding in the sun and wind, which also keeps the beneficial soil life alive. It also significantly reduces evaporation.
When applying compost and mulch, make sure to keep them at least 3 inches away from the stem of blueberry bushes as the moisture can encourage mold on the stem. Reapply compost every 1-2 months and mulch every 3-6 months.
Use mulches such as leaves, bark, and straw. However, pine needles and pine bark are some of the best mulches since blueberry plants prefer acidic soil (more on this later).
However, if your blueberry bush’s soil has poor drainage, make sure to address this first as compost and mulch can make the drainage worse in this case.
Generally, with poorly draining soils, potted blueberry plants can be repotted with fresh potting soil, while planted blueberries are a bit trickier. Typically, the best way is to provide lots of compost and let it naturally work its way into the soil over time.
If you’re working with heavy clay soil, the poor drainage and alkalinity will likely lead to growth issues for the blueberry bushes. In this case, it can be better to plant on mounds of soil instead of digging into it. For more information about clay soil and planting in mounds, check out my other post here.
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 (including 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. Plants do not distinguish between sources of nutrients. However, compared to commercial fertilizer, manure contains organic carbon which is the key to maintaining soil health, including the characteristics of cation exchange capacity, soil tilth, and water holding capacity.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 (source).
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.
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.
|Blueberry Variety||Hardiness Zones|
|Rabbiteye or Southern Highbush||7-9|
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 brown leaves).
When blueberry bushes get too hot (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 leaf and blossom 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)
Pests and Diseases
Blueberry leaves can turn brown and fall off due to pests and diseases such as blueberry maggots, fruit-worms, canker, root rot, and blight. Treat pests by using organic insecticides or companion plants, and diseases with organic fungicides.
Generally, you can tell if a blueberry plant 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.