I’ve been researching blueberry plants lately and I saw a common issue is blueberry bushes not growing new leaves or fruit. I wanted to find out more, so I did some research. Here’s what I found.
Blueberry bushes commonly won’t grow from improper watering, nutrients, and weather. Other causes are transplant shock, and pests and diseases such as aphids, leafrollers, and Verticillium wilt. For best results, plant blueberry plants in loamy soil, only water when the soil is dry, and provide acidic fertilizer.
So, while blueberry bushes won’t grow new leaves or fruit for several reasons, how can we identify what is causing it, and how can we fix it?
1. Improper Watering
Blueberry bushes do best when their soil stays moist. The best way to do this is to only water when the top 2-4 inches of soil is dry. This prevents both under and over-watering.
I check this by pushing my finger into the soil, up to the second knuckle.
However, there are times when we need to do more than watering.
Under-watered blueberry bushes are common when the soil is exposed to the hot and drying effects of the sun. In this case, the soil’s moisture dries out quickly which means the blueberry plant’s health declines in a matter of days or hours.
To combat under-watering, only water when the soil is dry and apply 2 inches of compost and 4 inches of mulch. Compost and mulch both dramatically retain soil moisture while promoting nutrients and beneficial soil life such as earthworms and mycorrhizal fungi.
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
Reapply compost on top of the blueberry plant’s soil every 1-2 months and mulch every 3-6 months. Some examples of mulches are wood chips, straw, leaves, or pine needles. Keep these amendments at least 3 inches from the plant’s stem as it can introduce mold.
Over-watered blueberry bushes are often not caused by too frequent watering, but by poorly draining soils. This causes the plant to develop yellow leaves and reduced growth.
If your plant’s soil is sopping wet for more than 24 hours, it’s likely poorly draining. You can also test this by doing a soil percolation test.
To combat over-watering, apply 2 inches of compost on the top of the soil. Compost fixes both under-watering and over-watering as it increases the soil’s water retention while breaking up larger clumps of soil, such as compacted clay.
Avoid using mulch on blueberry bushes until their soil is well-draining.
2. Extreme Weather
Too Hot
When blueberry bushes are exposed to temperatures of 90ºF and above, their leaves get too hot which stresses the plant and hinders the growth of leaves and fruit. In this case, the plant can’t send moisture from its roots to its leaves fast enough, which causes the leaves to dry, curl, brown, and drop.
Because blueberry bushes are temperate plants, they generally do best in cooler climates. However, some varieties such as Southern Highbush do well in warmer areas.
Aim to grow Northern Highbush blueberries in USDA hardiness zones 3-8, and Southern Highbush in zones 9-10.
Too Cold
Since blueberry bushes are largely temperate, it’s difficult for them to get too cold. For example, Northern Highbush blueberry plants can survive down to -30ºF to -40ºF. As blueberries are deciduous plants, it’s normal for them to lose their leaves in the fall and winter.
Keep in mind that when temperatures drop below 45ºF, plants typically enter a dormant state and have little to no growth. These are also called “Chill Hours”, which help the plant maintain dormancy and reserve nutrients and energy for springtime.
Not Enough Sunlight
Blueberry bushes require around 6 hours of sunlight a day. While some blueberry plants can grow with as little as 4 hours per day, you’ll often see reduced growth the fewer hours the plant receives.
Sunlight is critical for plant and fruit growth as it encourages photosynthesis, or how the plant gets its food and water.
If your blueberry plant’s leaves are curling or browning, it could be a sign it’s getting too hot and could use some shade from the afternoon sun. In this case, use the shade from other trees, structures, or items such as shade sails. 2+ hours of daily, partial shade will work.
3. Improper Nutrients
Nutrients are a central part of the growth of blueberry bushes, and too few or too many cause problems.
Let’s take a look at each of the three main things that can go wrong with nutrients for blueberry bushes.
- Lack of Nutrients
- Excess Nutrients
- Soil pH
A lack of nutrients is probably the most common of these three, but luckily the solution is simple. Apply fertilizer as directed or 2 inches of compost every 1-2 months.
| Nutrient Deficiency | Leaf Symptom |
|---|---|
| Nitrogen | Entire leaf is pale or yellow |
| Iron | Dark green veins, rest of the leaf is yellowing |
| Zinc | Yellow blotches |
| Manganese | Broadly pale leaves, foliage color looks mottled or smeared |
I prefer to use compost as it improves the water retention of the soil as well as the beneficial soil life. However, there are some good fertilizers out there.
To see which fertilizers I recommend for blueberry bushes, see my recommended fertilizer page.
Excess nutrients aren’t typically an issue unless you’ve over-fertilized your blueberry plant. In this case, provide your plant with a low-flow of water for 1-2 hours to flush and leach the nutrients deeper into the soil.
Soil pH is equally important as blueberry bushes require acidic soil to dissolve the nutrients before the plant’s finer roots can absorb them.
“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
Aim for a soil pH of around 4.5-5.5 for blueberries. If you’d like to see which pH meter I use and recommend, check out my recommended tools page.
4. Transplant Shock
If your blueberry bush was recently planted or repotted, and its leaf growth has slowed or stunted, it’s likely due to transplant shock. Transplant shock occurs when a plant is exposed to a new environment and has to establish a new root system.
In this case, the blueberry plant is stopping its canopy growth to instead regrow its roots.
Avoid transplanting blueberry bushes unless necessary as it can take up to 1 year for recovery.
To help avoid transplant shock, I like to plant with the following steps in mind:
- Have the new ground (or pot) prepared
- Remove as much of the plant’s current topsoil as possible, without damaging the shallow roots
- Grab the base of the plant’s stem and wiggle lightly
- Using your other hand, scoop up and support the rootball
- Lightly place the plant in the new ground (or pot) and fill it in
- Make sure the soil is at the same level on the plant as before
- Apply 2 inches of compost and 4-12 inches of mulch to the top of the soil
- Water generously and add more soil as needed
5. Pests
Aphids
Aphids are small bugs that suck the sap from underneath the blueberry plant’s leaves. This loss of sugar and moisture causes the leaves to curl, discolor, and drop. Aphids also deposit honeydew, which attracts ants.
If left unchecked, aphids can damage the plant’s health and potentially stunt or kill it.
These bugs come in multiple colors including white, yellow, or black, and usually are found hiding underneath the leaves. Typically, aphids won’t cause damage to the fruit, but because they suck sap from the plant, they can compromise its health and therefore reduce fruit size and yield.
The best ways to get rid of aphids (and mites) on blueberry plants is by spraying the infected leaves with water or neem oil, or releasing ladybugs (a natural predator of aphids and mites). Most often, a jet of water is enough to knock them off and kill them, but neem oil is a good second option.
For example, when my potted Kaffir lime tree had aphids, I found that a jet of water was sufficient to blast them off and prevent them from coming back. All I did was remove the hose nozzle and used my thumb to increase the pressure. Just keep in mind that too strong of a blast can damage the leaves.
Leafrollers
Leafrollers are caterpillars that feed on blueberry leaves, flowers, and green fruit. They normally appear in the spring, when blueberry plants begin to bloom. The most common leafroller to infest blueberry plants is Obliquebanded leafrollers.
The leafroller moths lay their eggs directly on blueberry leaves, on which the caterpillars hatch and begin eating. They hatch after about 10-12 days. Similar to other caterpillars, leafrollers use webbing to curl the leaf and hide in it.
You can manage leafrollers by using pheromone traps and encouraging natural predators such as spiders. Sprays are not recommended.
Unless leafroller numbers are very high, spraying is not necessary. Repeated or unnecessary sprays will harm natural enemies that are present, such as native parasitic and predatory insects and spiders that will reduce their populations.
Blueberry IPM Manual, Washington State University
6. Diseases
Root Rot
Root rot kills off the plant’s roots, which stresses the plant and causes symptoms such as fruit, flowers, and leaves yellowing, browning, and dropping. If not addressed, it leads to stunted growth or a dying blueberry plant.
You can typically tell if your blueberry bush has root rot if the soil is staying sopping wet and starts smelling. Allowing the soil to dry out or repotting blueberry plants with fresh potting soil are the best ways to amend this disease.
Verticillium Wilt
Verticillium wilt is a fungus that is similar to root rot in that it usually occurs in soils with excess water. Additionally, over-fertilizing can also cause it.
The most susceptible fruit crops that contract verticillium wilt are nightshade (tomatoes, peppers, and eggplants), but other fruiting plants such as blueberry bushes can also be infected. Symptoms of this disease include leaves wilting, yellowing, and dropping, and potentially branch dieback.
Prevent and treat verticillium wilt by pruning infected branches, avoiding excess water and fertilizers, and following best gardening practices.
