My family in California planted a raspberry plant a few months ago in the winter and recently told me they were dealing with some of the leaves dropping from the plant. My first idea was because they planted during a dormant month. But, here we are in spring and the plant is still dropping leaves. So, I did some research, and here’s what I found.
Raspberry plants normally drop their leaves in the fall and winter, but if they’re dropping leaves in the spring and summer, it’s likely due to improper watering, nutrients, or transplant shock. Some pests and diseases such as aphids, spider mites, blight, and root rot also cause leaf drop.
Let’s take a closer look at why raspberry plants drop leaves and how we can fix them.
1. Seasonal
Raspberry plants are deciduous plants, so it’s normal for them to go dormant and drop their leaves (usually yellow or red in color) in the fall and winter. This is a survival response for the plant to conserve its energy through the cold season, similar to hibernation.
By saving nutrients, the plant puts out much more growth and fruit in the springtime.
However, if your raspberry plant is losing its leaves in the spring or summer, it’s likely caused by one of the following issues.
2. Improper Watering
The best way to water raspberry canes is to only water when the top 2-4 inches of soil is dry. I check this by pushing a finger into the soil. This method helps prevent both under and over-watering.
Additionally, provide 2 inches of compost every 1-2 months and 4 inches of mulch every 3-6 months.
Under-Watering
If you check your raspberry plant’s soil and find it’s bone dry, the plant’s leaves are likely dropping from a lack of water.
When raspberry plants lack water, the roots don’t have enough moisture to send to the leaves. This causes the leaves to dry, curl, brown, and drop. Flowers and fruit will also drop.
Hot and dry weather can compound this issue. If not addressed, the raspberry cane will quickly die.
Along with only watering when the soil is dry, here are some more tips to provide sufficient water for your raspberry plant:
- Provide partial shade. Raspberries evolved as understory plants, so they prefer the partial shade of trees. If possible, provide your raspberry plants with at least 2 hours of shade during the afternoon.
- Apply 2 inches of compost. Compost increases the organic matter of the soil. 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. Mulch keeps the soil covered, providing essential protection from the sun, wind, and erosion. It also feeds earthworms, mycorrhizal fungi, and the like, which provide many benefits to plants (more on these later).
Over-Watering
On the other hand, if your raspberry’s soil is sopping wet for 1+ day, it’s likely due to over-watering.
Over-watering can occur from providing too much and too frequent water, but the more common cause is soil with poor drainage.
Let’s take a look at how to test your raspberry plant’s drainage, and how to amend it if needed.
How to Test Soil Drainage
The best way that I’ve found to test soil drainage is by doing a percolation test near the plant (outside its drip line or canopy).
Here’s how to do a percolation test:
- Dig a 1-foot by 1-foot hole
- Place a yardstick in the hole and fill it with water
- Wait an hour and measure how far the water has drained
Ideally, soil drainage should be around 2 inches per hour. But this is a guideline and not a rule, so don’t worry if yours is way off. For example, I did 3 different percolation tests across my yard and found drainage up to 5 inches per hour.
How to Amend Soil Drainage
If you find your soil is draining too fast or slow, the solution is the same. Apply compost!
Adding organic matter to the soil not only increases its water retention but breaks up the larger clumps of soil.
I recommend applying 2 inches of compost every 1-2 months. Simply place the compost on top of the soil, under the raspberry’s drip line. Over time, the compost will work its way into the soil. With assistance from the plant’s roots and the soil life, even heavy clay soil will be amended.
If you’d like faster results, you can also use sand to break up the clay.
Avoid using mulch on soil with poor drainage as it prevents evaporation and makes the issue worse. Once the soil is well-draining, apply 4 inches of mulch.
3. Improper Nutrients
Lack of Nutrients
| 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 |
When raspberry plants lack nutrients, they’re unable to maintain their health and develop issues such as leaves yellowing, browning, and dropping begin. Poor nutrients are also a cause of flower and fruit drop.
It’s most common for raspberry canes to drop leaves from a lack of potassium.
A lack of nutrients in the soil is typically caused by:
- Degraded Soil
- Imbalanced Soil pH
- Sandy Soil
Fortunately, compost fixes all of the above 3 causes (more on compost and fertilizer soon).
Excess Nutrients
When raspberry plants have excess nutrients (usually caused by over-fertilizing), their roots get chemically burned, causing the plant stress. If not addressed, the stress begins to kill the plant, starting with leaves browning and dropping.
If you believe you’ve over-fertilized your raspberry plant, the best thing to do is to flush the soil with lots of water.
This is called leaching, in which the water dilutes the nutrients/chemicals and pushes them further down into the soil (out of reach of the plant’s roots). Running your watering hose on low for 2-3 hours should do the trick.
How to Fertilize Raspberry Canes
The two main ways to fertilize raspberry plants are with fertilizer or compost. If you’re buying your fertilizer, I suggest avoiding chemical fertilizers if possible.
While chemical fertilizers work in the short-term, they often have long-term effects such as drying the soil. This not only causes issues with watering, but kills the beneficial soil life, stopping benefits such as improved water retention, nutrients, and pest and disease resistance for the plant.
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
The good news is that the majority of fertilizers and compost provide sufficient nutrients. Ideally, this includes the 3 main nutrients, nitrogen, phosphorus, and potassium (abbreviated as NPK), as well as secondary nutrients such as iron, zinc, and magnesium.
To see which fertilizers I do recommend, check out my recommended fertilizer page.
Alternative, if you opt for compost, I suggest the same recommendations above of 2 inches of compost every 1-2 months.
Imbalanced Soil pH
Raspberry plants prefer a soil pH of 5.6-6.2.
Most plants prefer a slightly acidic pH as it dissolves the nutrient solids in the soil and makes them accessible to 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
If the pH is outside of this range, raspberry canes aren’t able to absorb nutrients properly, leading to issues such as yellow, brown, and dropping leaves.
The best ways to check your soil’s pH are with pH strips or a meter. I prefer using a pH meter since they’re easy to use and affordable. To see which pH meter I use and recommend, check out my recommended tools page.
If you find your raspberry plant’s soil pH is too acidic (below 5.6), apply alkaline amendments such as wood ash, biochar, or lime.
For soil that’s too alkaline (above 6.2), apply acidic amendments such as sand, peat moss, and coffee grounds.
4. Transplant Shock
If your raspberry plant was recently planted or repotted, and its leaves are starting to curl, yellow, or brown, 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 raspberry plants 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 raspberry plant’s leaves. This loss of sugar and moisture causes the leaves to curl, yellow, and drop. They also cause some raspberry diseases.
When aphids suck the plant’s sap, they 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.
Spider Mites
Spider mites are similar to aphids, except they’re part of the spider family. They also feed on raspberry plants and cause leaves to yellow, red, and drop.
The main differences in appearance between aphids and spider mites are the spider mite’s ability to spin webs. These webs can cause damage to other parts of raspberry canes such as the twigs and fruit.
So, if you see small dots on your raspberry leaves, see if they’re depositing honeydew or webs and you’ll identify the pest.
Treatment
Here are the best ways to treat both aphids and mites:
- Spray with a jet of water (such as a hose with your thumb over the nozzle)
- Spray with neem oil
- Release ladybugs
When my 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.
Neem oil also works well as it traps the bugs in the oil, preventing them from moving. The bugs die off fairly quickly this way.
As ladybugs are a natural predator of both aphids and mites, encouraging them or releasing them in your garden is usually a good idea. Just make sure you have ladybugs and not the invasive Asian lady beetle.
You can also plant raspberry companion plants to encourage beneficial insects and deter pests. To learn more, check out my other post: The 10 Best Companion Plants for Raspberries.
6. Diseases
Root Rot
Root rot, also called Armillaria or Phytophthora Root & Crown Rot, is a root fungus that causes a raspberry plant’s leaves, blossoms, and fruit to droop, yellow, brown, and drop.
This disease typically occurs with poor drainage and waterlogged soil.
Avoid using sprays for root rot as it’s not effective.
There is no chemical control available for crown and root rot in the home garden. The most important control strategy is careful water management.
Clemson University Cooperative Extension Service
To prevent root rot, only water when the top 2-4 inches of soil is dry and promote well-draining soils.
To treat root rot, transplant your plants to an area with fresh, drier soil. Potted raspberry plants with root rot should be repotted with fresh potting soil. Planting in raised beds or hugelkultur mounds are also helpful in improving soil drainage.
For example, my potted Kaffir lime tree had root rot recently, which I was able to tell from the sopping wet soil and swampy smell. Fortunately, after repotting the tree with fresh potting soil and waiting a few days, the tree made a full recovery!
Verticillium Wilt
Verticillium wilt is a fungal disease in soil that causes raspberry leaves to yellow, brown, and drop. Over time, it can kill the plant. Already weakened plants from drought, over-watering, and other stressors are more likely to become infected from Verticillium wilt.
This fungal disease affects raspberry branches closest to the soil and works its way up the plant. The branches or canes appear blueish-black and die during the summer when the plant fruits.
There’s no cure for verticillium wilt, but proper water management can prevent and limit the disease. Drying out the soil can starve the fungus.
