A common issue I’ve seen in hot weather is our strawberry plants leaves start to curl. So, I looked into this more to try to prevent this from happening. Here’s what I found.

Strawberry leaves curl from under-watering, lack of nutrients such as calcium, extreme heat, diseases such as powdery mildew, and aphids. For best results, only water when the first 2-4 inches of soil is dry and apply compost and mulch. Manage disease and aphids with water, neem oil, or ladybugs when possible.

While strawberry plants get leaf curl from several causes, how can we identify the issue causing it, and how can we fix it?

1. Under-Watering

Our Strawberry Plant With Leaves Starting To Curl

The main reason strawberry leaves curl is a lack of water. The curling is a natural response to hold more moisture within the leaf. If left for too long, the leaves dry, brown, and drop from the plant.

You can tell if your strawberry plant is underwatered if its soil is bone dry. I like to check this by pushing a finger into the soil, under the plant’s drip line or canopy.

Fortunately, there’s a rule for watering that avoids both under and over-watering.

Only water when the first 2-4 inches of soil is dry. When you do water, deeply water down to 6-12 inches as the majority of the plant’s roots are found within this depth.

By deeply watering, we’re allowing all of the plant’s roots to absorb water and promoting deeper roots.

Remember: shallow watering leads to shallow roots. Short roots cause plants to become highly dependent on frequent watering and unstable in winds or other events. Deep watering promotes greater drought survival (accessing deeper water) and better anchorage in the soil.

Additionally, provide strawberry plants with 1 inch of compost every 1-2 months and 2 inches of mulch every 3-6 months.

Compost provides valuable nutrients and greatly retains soil moisture. It does this by improving the soil’s richness or organic matter, with every 1% increase leading to an additional 20,000 gallons of water held per acre.

Mulch also provides nutrients and is great for reducing evaporation, regulating soil temperature, and preventing erosion. Since strawberries evolved as ground cover plants in forests, they’re used to plenty of mulch in the form of fallen leaves and branches.

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

Even if your strawberry plant is watered properly, a lack of nutrients may be an issue.

2. Excess Heat and Dryness

USDA hardiness zone map
Source: USDA

Leaf scorch is another common issue that causes strawberry leaves to curl, and it’s usually caused by a combination of hot weather, direct sunlight, and wind.

In “The Resilient Farm and Homestead” by Ben Falk, he suggests creating microclimates to protect your plants from harsh conditions. You can do this by planting taller plants nearby to provide some shade or even using a shade cloth during the hottest parts of the day.

Strawberry plants that are too hot and dry get curling leaves as the moisture is leaving the leaf faster than the roots can supply it. And if the roots don’t have sufficient moisture, the leaves can curl, brown, wilt, and drop in a matter of days or hours.

Ideally, grow strawberry plants in USDA zones 4-9, depending on the variety. This is generally between -30ºF to 80ºF. Anything below or above this range can lead to issues such as leaf drop and the plant dying.

As most gardeners don’t experience temperatures below -30ºF, we’re going to focus on what to do in hot weather.

But first, it’s helpful to know how strawberry plants cool themselves so we can expand on it.

Strawberry plants keep themselves cool by sending moisture from their roots to their leaves and through a process called transpiration.

Transpiration is when plants exhale moisture (much like how we do). This is the reason why walking into a dense forest can feel extremely humid.

Professional German forester Peter Wohlleben mentions in his book, The Hidden Life of Trees, the top side of a leaf is like a solar panel (photosynthesis) while the bottom side is for breathing (transpiration).

Now, let’s take a look at how we can boost these two methods to help keep strawberry plants cool.

Tips for Hot Weather

  • Compost and mulch – as mentioned above, compost and mulch are two of the most important practices in any garden, especially regarding water retention and soil temperature control.
  • Partial shade – Since strawberries are natively ground cover plants, they prefer partial shade from the hot afternoon sun. You can create shade by using umbrellas, shade sails, or other plants. The best direction to shade from is the western sun as it’s the hottest.
  • Plant Density – To boost transpiration, create as much plant density around your strawberries. This raises the humidity and provides partial shade to the strawberry and its soil, significantly cooling it. A good way to do this is with companion planting.

3. Lack of Nutrients

Nutrient DeficiencyLeaf Symptom
NitrogenEntire leaf is pale or yellow
IronDark green veins, rest of the leaf is yellowing
ZincYellow blotches
ManganeseBroadly pale leaves, foliage color looks mottled or smeared
Source: The University of California Agriculture and Natural Resources

Calcium and boron deficiencies are the most common when it comes to strawberry leaves curling.

Lack of calcium can cause curling in strawberry leaves because calcium is a vital nutrient for plant growth and development. Without calcium, the cell walls become weak and the leaves may curl or show other signs of stress.

To add more calcium to your soil and help prevent calcium deficiency in your strawberry plants, consider adding crushed eggshells or bone meal to your soil.

A lack of boron can cause curling in strawberry leaves because it is an essential micronutrient for plant growth and development. When there’s a boron deficiency, plants may struggle to grow properly, which can lead to issues like curling leaves.

To add more boron to your soil and help prevent boron deficiency in your strawberry plants, consider adding organic material such as seaweed, banana peels, or other fruit peels.

And of course, there are other nutrients that may be lacking which can cause issues with your strawberries such as nitrogen, iron, zinc, and manganese.

However, it’s not always obvious which nutrient is deficient in the soil. For this reason, applying a regular boost of a complete nutrient profile is recommended.

The Best Way To Fertilize Strawberry Plants

The two main ways to fertilize strawberry plants are fertilizers and compost. While chemical fertilizers have nutrients in quantity, they often lack quality and cause issues such as dry soil and reduced soil health.

As a result, many gardeners are finding that organic fertilizers and compost are replacing chemical fertilizers. As mentioned in the watering section, use 1 inch of compost every 1-2 months around your strawberry’s drip line. Keep it at least 3 inches from the stem to avoid mold.

Either one you choose—you can check out the fertilizers and compost I recommend on my recommend fertilizer page.

However, nutrients aren’t everything.

Soil pH

ph scale couch to homestead

While nutrients are important, they cannot be absorbed by the plant properly if the soil pH is too acidic or alkaline.

Strawberry plants prefer a soil pH of 5.3-6.5.

The reason why most plants prefer a slightly acidic soil pH is because this is the pH that dissolves the nutrient solids. Only then are they accessible to the plant’s finer roots?

The best ways to check your soil’s pH are with 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 strawberry’s soil pH is too acidic (below 5.3), apply alkaline amendments such as wood ash, biochar, or lime.

For soil that’s too alkaline (above 6.5), apply acidic amendments such as sand, peat moss, and coffee grounds.

4. Aphids

a ladybug eating an aphid on a plant
A Ladybug Eating An Aphid

Aphids are small, soft-bodied insects that can cause curling leaves on strawberry plants by sucking the sap from the leaves, stems, and other tender parts of the plant.

As they feed, they inject their saliva into the plant tissue, which can cause the leaves to curl, become distorted, or develop yellow spots. In addition to the physical damage, aphids can also transmit viruses that can further harm your strawberry plants.

To prevent and control aphids on your strawberry plants, consider the following strategies:

  1. Monitor your plants regularly: Keep an eye on your strawberry plants and check for any signs of aphids or other pests. Early detection is crucial in managing infestations and preventing damage.
  2. Encourage beneficial insects: Introduce or attract beneficial insects, such as ladybugs, lacewings, and parasitic wasps, which are natural predators of aphids. You can do this by planting a variety of flowers and herbs that provide nectar and pollen for these helpful insects.
  3. Use insecticidal soaps or oils: If you notice a small infestation, you can use insecticidal soaps or horticultural oils, such as neem oil, to control aphids. These treatments are generally safe for both plants and beneficial insects, but be sure to follow the manufacturer’s instructions for proper application.
  4. Blast them with water: A strong spray of water from a hose can dislodge aphids from the plants and help keep their population in check. Be sure to do this in the morning so the plants have time to dry, which helps prevent fungal infections.
  5. Practice good garden hygiene: Remove plant debris, weeds, and any infected plants from your garden, as these can harbor aphids and other pests. Regularly clean your garden tools to avoid spreading pests and diseases.
  6. Use barriers or covers: Installing physical barriers, such as row covers or insect netting, can help keep aphids and other pests away from your strawberry plants.

5. Diseases

Powdery Mildew

powdery mildew spores on a leaf

This fungal disease, caused by Podosphaera aphanis, is characterized by a powdery white coating on the leaves, stems, and sometimes fruits of the strawberry 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.
  • Apply organic fungicides such as neem oil, sulfur, or potassium bicarbonate.

Mosaic Diseases

Mosaic diseases in strawberries are caused by various viruses, such as Strawberry Mosaic Virus (SMV) or Strawberry Mild Yellow Edge Virus (SMYEV). Infected plants may also experience reduced vigor, stunted growth, and poor fruit production.

Signs of Mosaic Diseases:

These viruses can cause a range of symptoms, including leaf curling, yellowing, and mottling of the leaves. In some cases, the leaves may become distorted or develop a mosaic-like pattern.

Prevention and Treatment

  • Purchase virus-free plants from reputable sources.
  • Regularly inspect your plants for symptoms and promptly remove and dispose of any infected plants to prevent the spread of the virus.
  • Control the insect vectors, such as aphids or thrips, that can transmit the virus by using insecticidal soaps, neem oil, or by releasing beneficial insects like ladybugs and lacewings.
  • Rotate your crops and avoid planting strawberries in the same location for several years in a row.

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