3 Reasons For Strawberry Leaves Turning Red (And Solutions)
Typically, the first sign that something’s not right with a plant is a change in the shape or color of its leaves. And naturally, strawberries aren’t an exception.
Indeed, analyzing strawberry leaves allows you to gauge the plant’s nutritional status (like if it’s missing any essential nutrients), identify any diseases, and determine its vegetation stage.
Well then, let’s talk about why strawberry leaves might turn red, why reddish-brown spots might appear on them, and what to do in such cases.
I can help you figure out the issues and what to feed or treat them with.
Reasons for Strawberry Leaves Turning Red
So, garden strawberries might turn red due to three main causes:
- Fungal diseases (like white or brown spot disease),
- Nutrient deficiencies (usually nitrogen, but other types of “starvation” can occur),
- Natural die-off of old foliage.
I’ll break down each cause separately.
According to some gardeners, strawberry leaves may sometimes turn red due to temperature fluctuations in the latter part of the summer, which is completely natural. Also, high soil acidity could be a factor. So, consider using wood ash more frequently as a fertilizer, as it can help to reduce the soil’s acidity!
Fungal Disease (Red Spots on Strawberry Leaves)
You’ll find red spots on the leaves if a fungal disease strikes your strawberry plants.
White and Brown Spot Disease in Strawberries
So, if your strawberry plants have contracted white spot disease (septoria), here’s what you’ll notice:
- First, you’ll spot small (about 2-3mm in diameter) round reddish-brown spots on the leaves (they won’t have any border at this stage),
- Then, these spots will turn gray-white and acquire a dark-red border,
Afterward, the spots will turn completely white and fall out (this disease’s main distinguishing feature).
- With a severe infestation, parts of the leaf will dry out, or the entire leaf will die off completely.
The disease also affects the stalks, runners, and flower stalks. On the stalks and runners, it appears as elongated brown spots, while the flower stalks not only turn brown but also thin out and droop.
The fruits suffer too, but they don’t rot. Instead, hard dark-brown spots form on them, significantly reducing the harvest quality.
The peak development of this fungal disease coincides with the fruit-bearing period (i.e., May-June).
What to Do if Your Strawberries Have Contracted White Spot Disease?
- Swiftly remove and burn (or remove from the plot) the leaves affected by the disease.
- Conduct preventative and eradicating sprays with fungicides (disease-fighting substances) in the spring (when new leaves just start to grow, i.e., before blooming) and at the end of summer fall (after harvest).
For instance, spray 1% of the Bordeaux mixture or 2% of copper sulfate. Alternatively, you might consider using Captan 50W fungicide for fungal disease prevention.
Avoid overcrowding your plants (the bushes should be well-ventilated, especially after rain or watering), and regularly, without mercy, remove weed invaders like chickweed, dock, knotgrass, or wild buckwheat.
It’s crucial to timely remove old and dead leaves – in other words, carry out spring and/or fall (post-harvest) strawberry pruning. The fact is fungi can survive on plant residues.
Grow disease-resistant varieties. Heads up! The following varieties have relative resistance to white and brown spot diseases released by the University of California, Davis, are as follows:
- UC Eclipse
- UC Golden Gate
- UC Keystone
- UC Monarch
- UC Surfline
Brown Spot Disease on Leaves
If your strawberries have contracted brown spot disease, you’ll notice blurry reddish-brown spots of irregular shape with black dots in the center and dry edges on the old leaves in the second half of the growing season. In other words, the affected leaves appear to be drying out.
As with white spot disease, the disease manifests particularly strongly in cases of overcrowded plantings, high humidity, and frequent heavy watering.
The fungi themselves overwinter on dead and green leaves. Therefore, protective and preventative measures against brown spot disease will be similar to those against white spot disease.
Nutrient Deficiency (Red, Purple Leaves)
Another cause of strawberry leaf reddening, where not just a small part (like a spot) but the whole leaf or most of it turns red, is a deficiency of a particular nutrient in the soil.
The color change in the case of “Nutrient deficiency” occurs due to the destruction of chlorophyll in the leaf tissues.
The lack of a specific nutrient can be caused by its absence in the soil and the lack of another element, which helps the first one to be absorbed.
For instance, nitrogen deficiency often occurs due to a lack of phosphorus in the soil. In contrast, iron deficiency manifests itself, for example, in the case of excess calcium in the soil.
Element | Deficiency Leaf Color |
Nitrogen | Pale, with red edges |
Phosphorus | Reddish-purple |
Potassium | Red, with browning edges |
First and foremost, the older leaves of garden strawberries turn red. This happens because when nutrients like nitrogen, phosphorus, potassium, and magnesium are deficient in the soil, the nutrients stored in the old leaves are transferred to the new ones.
However, other elements, such as iron cannot be reutilized, meaning nutrients aren’t transferred from old to new leaves. As a result, signs of deficiency will appear on the younger leaves.
If strawberry leaves start turning red in the summer, it’s a clear sign of nitrogen deficiency. In this case, it’s not just parts of the leaf, but the whole leaf turns red.
What to Do If Strawberry Leaves Turn Red Due to A Lack Of Nitrogen?
Of course, you need to fertilize with nitrogen:
Dose: urea/carbamide (0.53 ounces per 2.5 gallons of water) or ammonium nitrate (0.5-0.75 ounces per 2.5 gallons).
Tip! In cool weather (up to +15°C/59°F), it’s better to use ammonium nitrate. In contrast, in warmer weather (above 15-20°C/59-68°F), use urea/carbamide (under these conditions, it dissolves and is absorbed by the plant better).
In fact, it’s better to apply urea as a foliar feed (on the leaves). This way, the strawberry plant absorbs it better and faster.
Organic: Compost fertilizer or If you have fresh cow manure, you should use about one part of manure to 15-20 parts of water. The ratio of fresh bird droppings is one part droppings to 10-15 parts of water.
Phosphorus Deficiency
If the strawberry leaves are small (and getting smaller) and turn purple, this is a clear sign of phosphorus deficiency.
In other words, you need to feed the strawberries with a phosphorus fertilizer: potassium monophosphate (1 ounce per 2.5 gallons of water.).
Prepare a quick phosphorus feed from superphosphate (preferably double).
Actually, you can go ahead and fertilize your strawberries with dry phosphorus fertilizers, but you’ll only see the effects next year since these fertilizers aren’t quick-release. So, it’s best to do this after you’ve harvested, around late summer or early fall.
Applying the right fertilizers promptly can help clear up those visual signs of nutrient deficiency and boost plant growth and fruit production.
But remember, plants that have suffered severe nutrient deficiencies won’t reach the same levels as plants with a steady, adequate supply of nutrients.
Potassium Deficiency
Now, let’s talk about potassium. If your strawberry leaves turn red around the edges, showing a reddish-brown rim indicates potassium deficiency.
And guess what? When there’s not enough potassium, your berries also tend to be smaller.
So, what kind of potassium fertilizers can you use if the edges of your strawberry leaves turn red?
- Potassium sulfate (0.5 ounces per 2.5 gallons of water.). This sometimes also contains a bit of magnesium.
- Potassium magnesium (Potassium + Magnesium).
- Wood ash (4-7 ounces per 2.5 gallons of water).
Now, on to micronutrients like calcium and magnesium. Strawberry leaves can also turn various shades of red or brown if certain micronutrients are deficient, such as calcium and magnesium.
So, what’s the plan?
You can apply potassium magnesium (potassium and magnesium), calcium nitrate (nitrogen and calcium), or magnesium sulfate.
Natural Withering (Reddening) of Old Leaves in Fall
If you notice your strawberry leaves turning red in the fall, don’t sweat it! This is a completely normal and natural part of the old foliage withering process.
As the daylight hours decrease, the chlorophyll in the leaves naturally breaks down.
So, now you know why strawberry leaves turn red and what to do if you spot red or brown patches. Take good care of your garden strawberries, and you’ll enjoy consistent harvests. Best of luck, and here’s to tasty berries!