We have some family in Tennessee and some of their berry plants are getting red and purple leaves. They asked me if I knew anything about it, and while I had an idea, I did some research to give them the best answer I could. Here’s what I found.
Strawberries, blueberries, blackberries, and raspberries get red leaves from over-watering, improper nutrients, frost, and some diseases. These diseases are commonly leaf scorch, rust, and root rot. Promote proper soil drainage, apply compost, and insulate if you have an early or late frost.
Let’s take a closer look at how to identify which issue is causing red leaves, and how to fix it.
Over-watering is the most common reason berry plants get red leaves. Occasionally, leaves turn yellow as well. If the plant is stressed enough, it will even drop green leaves.
The best way to water berry 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 canopy. When watering, soak the soil down to 2 feet as the majority of the roots are found within this depth.
Even if you’re watering your berry plants properly, they can still become waterlogged without sufficient drainage. Waterlogged soil also quickly turns to root rot (more on this later).
Poor drainage is common in soils that are:
- High in clay
Compacted soil is common around construction sites as the weight of the vehicles compresses the soil’s particles—reducing the space in-between these particles and creating a near-solid layer, leading to poor drainage.
Heavy clay soil also has naturally compacting qualities as its particles are finer than sand or silt (see my graphic below). Clay soil that is also compacted is especially bad for plants and prevents water and roots from penetrating the soil.
Recessed soils are sunken compared to the rest of the area. Sometimes this is manmade, while other times it’s a result of being located at the base of a hill or other high-drainage areas.
You can tell if your soil is draining properly by doing a quick percolation test.
Here’s how to do one:
- Dig a 1-foot by 1-foot hole
- Put a yardstick in it and fill it with water
- After an hour, measure the amount of water drained on the yardstick
When digging a hole, make sure to dig outside of the drip line (canopy) of your plants to avoid damaging their shallow roots. Also, consider digging up to three holes around your property as there can be vastly different soil types depending on the location.
Ideally, the soil should drain at a rate of around 2 inches per hour. However, this is a guideline and not a rule, so don’t worry if yours is off. This test is primarily to determine if your soil drainage is excessively too fast or slow.
How to Fix Poor Drainage
If you find that your soil poorly draining, and is compacted or high in clay, apply 2 inches of compost every 1-2 months.
Over time, the compost works its way into the soil, breaking up the larger clumps while retaining the proper amount of moisture (and adding plenty of nutrients).
Note: Funny enough, the solution for soils that drain too quickly is also compost.
While compacted and clay soils require amending, recessed soils typically benefit from providing a slightly elevated soil—allowing gravity to assist with the drainage. Some examples of this are raised beds and hugelkultur mounds.
Raised beds are often the most expensive item in the garden, but a little secret is there are some nice affordable ones on Amazon.
Avoid using mulch until the soil is well-draining. While mulch is extremely helpful in reducing evaporation, regulating soil temperature, and preventing soil erosion, it can make poorly draining soil worse by preventing it from air-drying.
2. Lack of Nutrients
|Nutrient Deficiency||Leaf Symptom|
|Nitrogen||Entire leaf is pale or yellow|
|Iron||Dark green veins, rest of the leaf is yellowing|
|Manganese||Broadly pale leaves, foliage color looks mottled or smeared|
Berry plants also get red and purple leaves from nutrient deficiencies, especially from a lack of nitrogen or phosphorus. The table above shows some telling signs of certain nutrient deficiencies with a common symptom being yellow leaves.
The best way to fertilize berry plants is to provide an acidic fertilizer with a balanced NPK (nitrogen, phosphorus, and potassium, the three main nutrients of plants).
Alternatively, you can provide compost, which has other benefits such as improving drainage and the soil’s health.
To see which fertilizers and compost I recommend, see my recommended fertilizer page.
Imbalanced Soil pH
While nutrients are essential, a balanced soil pH is needed for proper uptake. And like most plants, berry plants prefer a slightly acidic soil pH. This is because an acidic pH is required to dissolve the nutrient solids and make 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
|Berry Plant||Preferred Soil pH|
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 berry plant’s soil pH is too acidic, apply alkaline amendments such as wood ash, biochar, or lime.
For soil that’s too alkaline, apply acidic amendments such as sand, peat moss, and coffee grounds.
Berries are largely temperate fruits, so they prefer cooler climates. If they’re exposed to extreme heat and dryness (above 90ºF), they’ll often develop conditions such as leaves curling, drooping, drying, browning, and dropping.
On the other hand, cold weather and frost cause berry plant leaves to discolor (usually red or yellow) and drop from the plant.
|Berry Plant||Growing Zones|
Leaves discoloring and dropping usually isn’t a problem if it’s autumn or winter as this is a normal response of plants going into dormancy (also called deciduous plants).
However, if it’s spring or summer, and your berry plant’s leaves are turning red or yellow, here’s what you can do to help.
Tips for Early or Late Frost
When berry plants have an early or late frost, they’re unprepared to handle the cold. This is because they’re either not yet dormant, or have just come out of dormancy. Either way, the plants get stressed and shocked from the quick change in weather, leading to discolored and dropping leaves.
If it’s bad enough, the berry plant can die.
Here are some tips to help prevent this:
- Provide mulch – mulch has so many benefits, and one of them is providing insulation from hot and cold weather. This protects the berry plant’s sensitive roots, which help regulate the temperature for the rest of the plant.
- Move indoors – if you’re growing your plant in a container, move them indoors. Aim to place them beside a southern-facing window for maximum warmth (if you live in the southern hemisphere, this is northern-facing)
- Greenhouses – similar to moving indoors, you can also relocate your berry plants into a greenhouse. And you don’t need a large greenhouse, you can make one of just about any size by providing a transparent or translucent enclosure. Bonus points if you use a compost pile’s natural heat to raise the temperature of the greenhouse.
Root rot, also called Phytophthora Root & Crown Rot, is a root fungus that causes berry leaves, blossoms, and fruit to droop, yellow, red, brown, and drop.
This disease typically occurs in areas with poor drainage. To prevent and treat root rot, promote well-draining soils and transplant young plants with fresh soil if necessary. Raised beds are also helpful in improving soil drainage.
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
My potted Kaffir lime tree had root rot recently, which I was able to tell based on 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!
Rust is a fungal disease that turns leaves pale green and yellow and causes orange blisters underneath the leaves. This is commonly why it’s called “orange rust”. Rust commonly doesn’t kill plants, but it can significantly reduce their yield.
As with most fungal plant diseases, rust is common in warm and wet weather (around 50ºF to 70ºF).
Rust can be managed with proper gardening practices such as pruning and spacing for airflow and sunlight (reducing fungal buildup). If desired, there are some organic sprays available as treatment.
Red raspberries are immune to rust, and blackberry varieties such as Eldorado, Raven, and Ebony King are resistant. There are no known black raspberry varieties that are resistant to rust.
Leaf scorch is a virus that causes berry leaves to turn red and spotted. Other symptoms include blossoms, stems, and foliage dying. It’s transmitted through aphids, so proper aphid and mite management is helpful in treating it.
Some varieties such as Berkeley blueberry are more susceptible than others.
While the above diseases are common across strawberries, blueberries, blackberries, and raspberries, let’s now take a look at the specific diseases berry plants get that cause red leaves.
Other Strawberry Plant Diseases
Red Stele (Red Core) is a fungal disease (Phytophthora fragariae) in the soil that turns strawberry leaves red, yellow, or orange. It’s mainly managed and treated by promoting proper drainage.
While Red Stele can be avoided by amending soil to be well-draining, here are some strawberry varieties that are resistant to Red Stele:
Other Blueberry Plant Diseases
Red Ringspot Virus is another virus that turns blueberry leaves red, this time showing as small circles which join into larger spots. This disease affects varieties including highbush, southern highbush, and rabbiteye, as well as cranberry plants.
Aphids and mites are also thought to transmit red ringspot, but it hasn’t been confirmed. Grafting and cuttings are also possible methods of transmission. Varieties “Star” and “Jewel” are found to be resistant.
While there are several causes of red leaves on berry plants, my family narrowed it down to drainage and/or nutrients. They’re looking at amending their soil and providing compost to fix these issues. In another season or two, they’ll let me know how it’s going!