Blackberry Plants Not Growing: 5 Causes & Fixes

I recently planted a blackberry plant in my backyard and noticed it’s not growing much, or maybe not at all. While it’s early in the spring season, I was still worried. So, I did some research to see what was happening. Here’s what I found.

Blackberry plants commonly won’t grow from improper watering, nutrients, and weather. Other causes are transplant shock as well as pests and diseases such as aphids and powdery mildew. For best results, plant blackberry plants in loamy soil, only water when the soil is dry, and provide slightly acidic fertilizer.

So, let’s figure out which of these reasons is causing your blackberry plant not to grow and how to fix it.

1. Improper Watering

Under-Watering

Under-watering is one of the most frequent reasons blackberry plants don’t grow and it’s especially common if you get hot and dry summers.

The best way to water blackberry plants is to only water when the top 2-4 inches of soil is dry. I check this by pushing a finger into the soil, under the plant’s drip line. When watering soak the ground at least 2 feet deep.

Since over 90% of the plant’s roots are found within the first 2 feet of soil, soaking the soil ensures the majority of the roots get water.

Deep watering like this encourages the plant to grow deeper roots, which provides it with deeper water and better anchorage.

On the other hand, shallow and frequent watering encourages shallow roots and makes drought stress and wind damage more likely.

Apply 2 inches of compost and 4 inches of mulch under the plant’s drip line. Reapply compost every 1-2 months and mulch every 3-6 months. Keep both materials at least 3 inches from the blackberry plant to avoid mold buildup.

Compost provides essential nutrients and increases the soil’s water retention. Every 1% increase in the soil’s organic matter leads to an additional 20,000 gallons of water held per acre. Compost also feeds the soil life, leading to benefits such as increased nutrients and pest and disease resistance.

Mulch dramatically reduces evaporation, regulates soil temperature, and prevents soil erosion. Since blackberry plants evolved as understory species in forests, they prefer plenty of mulch in the form of fallen leaves and branches.

As permaculture guru Geoff Lawton says, a forest grows on a fallen forest.

Both compost and mulch also amend soils that drain too quickly. But what happens if the soil has poor drainage?

Over-Watering (Poor Drainage)

While both under and over-watering can be prevented by only watering when the soil is dry, if the soil has poor drainage it can become waterlogged and lead to issues such as root rot (more on this later).

Over-watered soils are most often a result of ground that’s depressed, compact, or high in clay.

Here are some quick steps to fix poorly draining soil.

1. Test
2. Amend
3. Mulch

Percolation Test

A good way to test your soil’s drainage is by doing a percolation test.

1. Dig a 1-foot by 1-foot hole
2. Place a yardstick in the hole and fill it with water
3. After an hour, measure the water line on the yardstick

The goal for proper drainage is about 2 inches per hour. However, this is a guideline and not a rule, so don’t worry if yours is way off. This is just a way to see if your soil has poor or fast drainage.

I recommend digging at least 3 different holes across your property as some areas might have much better drainage than others.

Amend Poorly Draining Soil

Once you determine your soil’s drainage, it’s time to amend it.

Interestingly, the solution for both poor drainage and fast drainage is the same—compost.

Compost not only breaks up the clumps of ground in poorly-draining soil, but its organic matter retains water in fast-draining soils.

As mentioned above, I recommend providing your blackberry plants with 2 inches of compost every 1-2 months. Over time, the compost will work its way into the soil.

If you can’t wait for the compost to do its job on the soil, you can also move your blackberry plant to an area with better drainage such as a raised bed or mound of soil.

Potted blackberry plants that have poor drainage should be amended by repotting them with fresh potting soil.

Provide Mulch

Once your blackberry plant has well-draining soil, provide 4 inches of mulch to give it a big boost of water retention and protection from the elements.

Some good mulches for blackberry plants are straw, leaves and pine needles.

2. Heat or Frost Stress

Blackberry plants are natively from temperate climates, so they prefer cooler environments such as USDA hardiness zones 4-10. 

To find your hardiness zone and see if it’s compatible with blackberries, see the USDA hardiness zone map.

However, this is a generalization as some varieties prefer warmer or colder zones.

Climates that are too cold (below zone 4) or those that are hot and dry quickly pose a problem for blackberry plants.

Keep blackberry plants in a cool and mild climate if possible. If the sun is too hot, and the tips of the leaves are curling and browning, provide shade or move potted blackberries indoors. When bringing them indoors, take care to avoid the hot and dry air from the central heat.

As always, make sure your blackberry plants get at least 8 hours of direct sunlight daily (aim for the morning sun as it’s cooler).

For ways to combat curling and browning leaves on blackberry plants, check out my other posts: Why Blackberry Plant Leaves Curl and 4 Ways to Fix Brown Leaves on Blackberry Plants.

Hot Weather

In hot and dry areas such as California, Arizona, Nevada, and parts of Texas, blackberry plants lose moisture from their leaves and soil quickly. Normally, blackberry plants do best in temperatures under 80ºF. Any hotter and they may stop growing.

Much like humans, plants cool themselves by exhaling moisture (called transpiration). Plants also keep themselves cool by sending moisture from their roots to their leaves.

This becomes a problem when the climate is too hot and dry. Essentially, the transpiration and root moisture can’t keep up and cool the plant and its leaves.

So, the hotter and drier the weather, the more energy the plant uses to transpire and survive, and the less energy it has to use to establish its root system and grow. This drain of resources can quickly stunt or kill the plant.

The best practices to help your blackberry plant survive hot and dry weather are to provide it with sufficient water, compost, and mulch. Additionally, give it partial shade from the west (as the afternoon sun is the hottest).

Cold Weather

If temperatures fall below -20ºF to -30ºF (the standard zone 4 minimum temperature), blackberry plants will likely start to die.

For outdoor blackberry plants, you can insulate the plant and its roots by providing it with mulch. You can also use windbreaks such as walls or other plants to reduce the effects of windchill. Greenhouses or high tunnels will also work.

I would suggest not moving potted blackberry plants indoors during the winter as they typically require 300-800 chill hours to fruit properly once spring arrives. Chill hours are the number of hours below 45ºF.

Since indoor temperatures rarely get this low, it’s normally not a good idea to bring them inside.

Another issue with moving a blackberry plant indoors is that the central heat indoors can dry out the plant quickly.

I found out about the effects of central heat the hard way.

We had a surprise snowstorm last year here in Austin, Texas, and I moved my potted Meyer lemon tree inside. However, it quickly started losing its leaves. After moving it into a cooler room, it quickly started growing new leaves (see the photo below).

When it comes to sheltering your potted blackberry plant during temperatures below -30ºF, move it to a basement or another cool, sheltered location. Try to keep the temperature under 45ºF to maintain the plant’s chill hours if possible.

3. Improper Nutrients

Excess Nutrients

When blackberry plants get too many nutrients, their roots are chemically burned which stresses the plant and causes a decline in health. Excess nutrients are often caused by fast-release chemical fertilizers as compost isn’t potent enough.

It’s more common for blackberry plants to not grow or not produce fruit because of an excess versus a lack of nutrients.

If you believe you’ve over-fertilized your blackberry plant, I suggest removing as much of the fertilizer as possible via leaching.

To leach, heavily water your blackberry plant’s soil to dilute the existing fertilizer and allow it to flow deeper into the soil (and out of reach of the plant’s roots). You may have to do this at least a few times.

Avoid leaching if your soil has poor drainage as the soil can become waterlogged.

In this case, either apply generous amounts of compost and garden soil to dilute the chemical nutrients, or repot the plant with fresh potting soil (for potted blackberry plants).

A 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

Source: The University of California Agriculture and Natural Resources

If you haven’t fed your blackberry plant in the past several months, there’s a good chance it may be dying from a lack of nutrients.

Symptoms of a lack of nutrients depend on the deficiency.

For example, blackberry plants commonly get a nitrogen deficiency and get lightly colored or yellow leaves.

Let’s take a look at the ideal way to prevent a lack of nutrients for your blackberry plants.

The Best Way To Fertilize Blackberry Plants

If you decide to use a chemical fertilizer, opt for one with a balanced NPK (nitrogen, phosphorus, and potassium), such as a 10-10-10.

Each brand has different percentages, so follow the instructions on the label for the best results.

If you’d like to see which fertilizers I recommend, check out my recommended fertilizer page.

Alternatively, you can use compost.

I recommend applying 1 inch of compost every 1-2 months under the plant’s drip line followed by 2 inches of mulch.

Keep in mind that while nutrients are essential, they aren’t everything.

Imbalanced Soil pH

Blackberry plants prefer a soil pH of 5.6 to 6.5.

The reason blackberries (and most plants) prefer a slightly acidic soil pH is that it dissolves the nutrient solids in the soil, making them more 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, Instructional Support Specialist, Department of Forest and Natural Resources Management

When blackberry plants have an imbalanced soil pH, they develop issues such as discolored and dropping leaves. Additionally, their flowers and fruit drop early and the plant is more likely to develop other issues.

Two good ways to test your soil’s pH are with pH strips or a meter. I prefer using a pH meter since they’re affordable and easy to use. To see which pH I recommend, check out my recommended tools page.

If you find your blackberry plant’s soil is too alkaline (above 6.5), provide acidic amendments such as peat moss, sand, and coffee grounds.

On the other hand, if your soil is too acidic (under 5.6), provide alkaline amendments such as charcoal, wood ash, and lime.

3. Transplant Shock

If your blackberry plant 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 blackberry plant is stopping its canopy growth to instead regrow its roots.

Avoid transplanting 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:

1. Have the new ground (or pot) prepared
2. Remove as much of the plant’s current topsoil as possible, without damaging the shallow roots
3. Grab the base of the plant’s stem and wiggle lightly
4. Using your other hand, scoop up and support the rootball
5. Lightly place the plant in the new ground (or pot) and fill it in
6. Make sure the soil is at the same level on the plant as before
7. Apply 2 inches of compost and 4-12 inches of mulch to the top of the soil
8. Water generously and add more soil as needed

5. Pests

Slugs & Snails

Slugs and snails love to munch on the tender leaves and fruits of blackberry plants, leaving behind holes and ragged edges.

Here’s some quick info on how to tell if your blackberry plant is getting eaten by slugs and snails and how to prevent or remove them.

Signs of Slugs and Snails:

• Irregular holes in leaves and fruits
• Slimy trails (known as slime trails) on or around the plants

Prevention and Treatment:

• Encourage natural predators like birds, frogs, and beetles by creating a diverse garden habitat.
• Use beer traps to catch the pests. Simply fill a shallow container with beer and bury it at soil level. Slugs and snails will be attracted to the beer, fall in, and drown.
• Apply diatomaceous earth or crushed eggshell barrier around the plants. These materials have sharp edges that deter slugs and snails from crossing.
• Plant companion plants such as garlic, onions, and cover crops to help repel them.

Pro-tip: If you have ducks, let them have a go at the slugs and snails (they love them)! Just keep an eye on them to make sure they don’t damage your blackberry plants.

Aphids

These tiny sap-sucking insects can cause serious damage to your blackberry plants by sapping the plant’s nutrients and spreading viruses.

Signs of Aphids:

• Yellow, curling, or misshapen leaves
• Stunted growth
• Black sooty mold on leaves (a result of the aphids’ sticky honeydew excretion)

Prevention and Treatment:

• Introduce beneficial insects such as ladybugs and lacewings, which are natural predators of aphids.
• Spray plants with a homemade solution of water and a few drops of dish soap to help dislodge and kill the aphids. Be sure to rinse the plants with clean water after a few hours to prevent soap buildup. You can also use neem oil.
• Use a strong jet of water to knock aphids off the plant (this is what worked when I removed aphids from my Kaffir lime tree). Repeat as needed

Spider Mites

These minuscule pests can be difficult to spot, but they can cause severe damage to your blackberry plants by sucking the plant’s juices and leaving behind tiny, discolored spots on the leaves.

Signs of Spider Mites:

• Fine webbing on the undersides of leaves
• Tiny yellow, brown, or white spots on leaves
• Overall plant discoloration and decline

Prevention and Treatment:

• Keep plants well-watered and stress-free, as spider mites are attracted to stressed plants.
• Release ladybugs or predatory mites, like Phytoseiulus persimilis, to naturally control the spider mite population.
• Spray plants with a mixture of water and a few drops of dish soap to help dislodge and kill the mites. Remember to rinse the plants with clean water after a few hours. Neem oil also works for spider mites.

6. Diseases

Verticillium Wilt

This fungal disease is caused by the soil-borne fungi Verticillium dahliae and Verticillium albo-atrum. It can lead to blackberry plants wilting, yellowing leaves, and even plant death.

Signs of Verticillium Wilt:

• Yellowing, curling, or wilting leaves, starting from the bottom of the plant
• Stunted plant growth
• Brown discoloration in the plant’s vascular tissue (visible when the stem is cut)

Prevention and Treatment:

• Choose resistant blackberry cultivars, such as ‘Triple Crown’.
• Practice good crop rotation, avoiding planting blackberries in the same spot where tomatoes, potatoes, peppers, or eggplants have been grown in the past 3-4 years.
• Remove and destroy infected plants to prevent the spread of the disease.
• Improve soil health by adding compost and other organic matter.

Powdery Mildew

This fungal disease, caused by Podosphaera aphanis, is characterized by a powdery white coating on the leaves, stems, and sometimes fruits of the black3berry plant.

Signs of Powdery Mildew:

• White, powdery coating on leaves, stems, and/or fruits
• Curling, distorted, or stunted leaves
• Poor fruit quality and reduced yields

Prevention and Treatment:

• Provide adequate sunlight and air circulation by proper plant spacing and pruning.
• Water plants in the morning, so the foliage dries quickly, and avoid overhead watering.
• Remove and discard infected plant material to reduce the spread of the disease.
• Apply a sulfur-based fungicide or a homemade solution of 1 tablespoon baking soda, 1 tablespoon horticultural oil, and 1 gallon of water. Spray the plants, making sure to cover all surfaces.

Botrytis Fruit Rot (Gray Mold)

Caused by the fungus Botrytis cinerea, this disease can result in moldy, rotting fruits and can also affect flowers and leaves on blackberry plants.

Signs of Botrytis Fruit Rot:

• Soft, brown spots on fruits, which may become covered in gray, fuzzy mold
• Wilted or brown flowers
• Moldy or discolored leaves

Prevention and Treatment:

• Improve air circulation by spacing plants properly and removing any weeds or unnecessary foliage.
• Water plants at the base, avoiding wetting the leaves and fruits.
• Remove and discard any infected or rotting fruits, flowers, or leaves.
• Use a preventative organic fungicide, such as copper or sulfur-based products, when conditions favor the disease (cool and wet weather).

A Note on Pesticides, Fungicides, and Herbicides

We recently had an issue with caterpillars eating our basil plants and we were about fed up. Every time we’d plant basil, the caterpillars ate it.

Fortunately, we found an organic spray at our local nursery that’s made from fermented rum. The day after spraying, we’d find dead caterpillars on the soil.

If you’d like to find out more about this organic spray, you can find it here on Amazon.

So, what’s my point here?

Even though chemical sprays and fertilizers are an easy way out, like all easy and convenient things, there are usually long-term costs. Namely to the plants, soil, and surrounding beneficial life.

Before using conventional sprays, weigh the pros and cons and consider trying organic or permaculture-based treatments first.

To give you a head start, Stefan Sobkowiak – The Permaculture Orchard has a great video on a safe, homemade, and most importantly—effective fungicide (hint: the secret ingredient is whey).