I’m doing a permaculture design for a client and they needed help with their blueberry plants. They told me the leaves are drooping and starting to brown. I had an idea of what was causing the issue, but I did some research to confirm. Here’s what I found.
Blueberry bushes get droopy and wilting leaves from improper watering, hot weather, transplant shock, and diseases such as root rot and Verticillium wilt. To prevent droopy leaves, only water when the top 2-4 inches of soil is dry and apply compost and mulch. Also, provide partial shade when temperatures exceed 90ºF.
Let’s take a look at how we can identify the issue causing drooping and wilting leaves on blueberry bushes, and how we can fix it.
1. Improper Watering
The best way to water blueberry bushes is to only water when the top 2-4 inches of soil is dry. I check this by pushing a finger into the soil.
By watering in this way, we’re preventing both under and over-watering.
Under-Watered
When blueberry bushes are under-watered, their roots don’t have enough moisture to pass to the leaves. As a result, their leaves dry, droop/wilt, curl, brown, and drop from the plant.
Under-watering is made worse when the climate is hot and dry (more on this later). This further speeds up the evaporation of water from the soil, drying the blueberry plant’s leaves in a matter of days or hours.
So, while following the rule of only watering when the top 2-4 inches of soil is dry is best, you can also slow the evaporation of water from the soil and keep it protected from the elements.
Apply 2 inches of compost every 1-2 months. Compost increases the soil’s richness, provides valuable plant nutrients, and promotes healthy soil life. For example, every 1% increase in the soil’s organic matter leads to an additional 20,000 gallons of water held per acre.
Apply 4 inches of mulch every 3-6 months. Mulch dramatically reduces evaporation, regulates soil temperature, and prevents erosion. Like compost, mulch feeds 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
Over-Watered
Blueberry bushes that are over-watered show symptoms such as leaves drooping/wilting, yellowing, and dropping. If the issue isn’t corrected, it can lead to a dying blueberry bush.
You can tell if a blueberry bush’s soil is over-watered if it’s staying sopping wet for more than 24 hours. Ideally, soil should have moisture similar to a wrung-out sponge.
As with under-watering, aim to only water when the top 2-4 inches of soil is dry.
While over-watering can be caused by watering too frequently, it’s more commonly caused by poorly draining soil. This is typical with soil that is high in clay.
Let’s take a look at how to identify, test, and amend poorly draining soil.
Poor Drainage
- Check – Initially check the soil’s drainage by feeling if the top 2-4 inches of soil is dry or wet. If it’s sopping wet for more than 24 hours, it’s getting over-watered. In this case, move to step 2.
- Test – The best way I’ve found to test soil is by doing a percolation test (pictured above). To do this, dig a 1-foot by 1-foot hole, place a yardstick in, and fill the hole with water. Wait an hour and measure how many inches the water has drained. The goal should be around 2 inches per hour.
- Amend – If the soil is draining well under or over 2 inches an hour, amend it by placing 2 inches of compost on top of the soil. Compost fixes both poor and fast drainage as it retains water while breaking up the larger chunks of soil.
2. Hot Weather
Blueberry bushes are temperate, so they prefer a moderate spring and summer, and a chilly fall and winter. For this reason, most blueberry varieties (such as Northern Highbush) grow best in USDA hardiness zones 3-8.
However, a few varieties such as Southern Highbush can be grown in zones 9-10.
When soil is exposed to the hot and drying effects of the sun, it loses moisture quickly. This leads to the blueberry plant having insufficient water to send to its leaves.
Other times, the roots might have enough water, but the heat is too extreme and the plant can’t send moisture to cool the leaves fast enough. Typically, this is around 90ºF and above.
In either case, blueberry plants affected by the heat develop symptoms similar to under-watering. These symptoms include fruit, flowers, and leaves drying, drooping/wilting, curling, browning, and dropping.
Hot Weather Tips
- Apply compost and mulch – as mentioned in the watering steps, provide 2 inches of compost and 4 inches of mulch to drastically reduce the effects of the hot and dry weather.
- Provide partial shade – blueberry plants evolved as understory species, so they prefer to have a few hours of afternoon shade. You can do this by planting trees, using shade sails, or planting on the north or east side of your property.
- Plant on the northern or eastern side of your property – In the northern hemisphere, the north and east sides of properties are usually the coolest and have the least amount of sun. Just make sure your blueberry bush gets at least 4 hours of daily sunlight (ideally 6+ hours).
3. Transplant Shock
If your blueberry bush was recently planted or repotted, and its leaves are wilting or drooping, 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.
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
4. Diseases
Root Rot
You can typically tell if your blueberry bush has root rot if the soil is staying sopping wet and starts smelling. As mentioned earlier, allowing the soil to dry out or repotting blueberry plants with new 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.
Sources
- https://www.gurneys.com/growing-blueberry-plants
- http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/DISEASE/pchphytoph.html
