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7 Reasons Why Dahlia Leaves Are Curling (And How To Fix)

Dahlias stand out from other flowers due to their numerous petals forming distinct patterns, making them a popular choice for gardens and homes. However, Dahlias, like any plant, can encounter issues.

Fluctuating temperatures, intense sunlight, or irregular watering can stress Dahlias, leading to curled leaves – a sign they need attention. To keep them thriving, place them where they’re protected from strong midday sun and maintain steady soil moisture.

1. Temperature Stress

Dahlia leaves curling

Dahlia leaves curling because of dry air.

Temperature stress is a common reason for dahlia leaves curling. Dahlias are used to milder temperatures in their native habitat, which is why they’re often kept indoors in cooler regions. If they get too cold, their leaves might start to curl.

Too much heat can also cause problems. If it gets really hot, either inside or outside, the leaves might curl downwards or even wilt.

Here’s what you can do:

  1. Keep your dahlia in a temperature range of 60-95°F (15-35°C).
  2. Avoid putting it in spots where the temperature might go over 100°F (38°C).
  3. Keep it away from heaters or air conditioners.
  4. Don’t place your dahlia in an area with cold drafts.

2. Underwatering

Dahlia leaves curling because of underwatering.

Dahlia leaves curling because of underwatering.

Dahlias aren’t plants that can handle drought well. Their big leaves lose a lot of moisture daily, so they need regular watering.

Indoor air is usually drier than outside, causing the soil in pots to dry out quicker. This can lead to the leaves curling due to lack of water.

To see if your dahlia needs water, check the soil. If the top inch is dry, it’s time to water it. But be careful not to water it too much, as this can cause root rot. That’s why it’s best to use well-drained soil and pots with holes at the bottom.

Here’s what you can do:

  1. Water your dahlia when the top inch of soil is dry.
  2. When watering, use enough water so it runs out of the drainage holes.
  3. Avoid overwatering to keep the roots healthy.

3. Pests

Insects can be another reason why dahlia leaves curl. Several pests attack this plant, but aphids, mealybugs, thrips, and scale insects are the most common. These pests cling to the leaves and drink the plant’s sap, causing the leaves to twist and deform.

Spider mites deserve extra attention. These tiny bugs, visible only under a magnifying glass, also suck the sap from the dahlia, leading to leaf curl.

Here’s what you can do:

  1. Inspect your plant carefully, using a magnifying glass to check for mites.
  2. If you spot aphids, mealybugs, thrips, or scale insects, first rinse them off with water.
  3. After a day or two, spray the plant with a water-based solution of horticultural oil.

4. Lack of Sunlight

Dahlia leaves curling due to lack of light.

Dahlia leaves can curl due to not getting enough light. Often, the leaves curl downwards when they don’t receive enough direct sunlight. This is a common issue indoors, where direct sunlight is limited.

If your dahlia doesn’t get enough direct sun, it will start to stretch out. This growth uses up the plant’s internal energy, weakening it. As a result, not only will the leaves curl downwards, but the plant will also be more prone to fungal diseases.

Here’s what you can do:

  1. Make sure your dahlia gets at least 6 hours of direct sunlight. Place it near a south-facing window for best results.
  2. Gradually introduce your dahlia to more sunlight.
  3. If you don’t have a spot with enough natural light, consider using artificial lighting.

5. Diseases

Root rot is a particularly challenging issue for dahlias because it’s hard to notice in the early stages. Often, the leaves begin to curl and yellow when some roots have already rotted. In such cases, immediate action is crucial to save the plant.

Fungal diseases like leaf spot or mold can also cause dahlia leaves to yellow or brown. These too require prompt treatment.

Here’s what you can do:

  1. If root rot is causing the leaves to curl, take the dahlia out of its pot. Clean and wash the roots, then cut away any rotten parts. Treat the cut areas with a 10% solution of hydrogen peroxide.
  2. Repot the dahlia in fresh, well-drained soil. Make sure the pot has drainage holes.
  3. Let the soil dry out to about an inch deep before watering again.
  4. If a fungal disease is the problem, remove any damaged leaves and spray the plant with a copper-based fungicide.
  5. Ensure good air circulation around your dahlia.

6. Nutrients Issue

Dahlias need plenty of nutrients to produce large, seed-filled flowers. Initially, they use nutrients from the soil, but over time, the soil can become depleted, leading to a lack of fertilizer. This can result in leaves curling.

Also, since dahlias are annuals, they have to regrow their above-ground parts each year, which takes a lot of energy. So, they require a good amount of fertilizer annually.

Here’s what you can do:

  1. In early spring, fertilize your dahlia with a slow-release, all-purpose fertilizer.
  2. Ensure the fertilizer includes nitrogen, potassium, and phosphorus.
  3. After the dahlia flowers, give it a one-time dose of liquid fertilizer.
  4. Don’t fertilize the dahlia during winter.

7. Harsh Sun

Dahlia leaves curling due to scorching sun.

Dahlia leaves curling due to scorching sun.

Dahlia leaves can curl inward if they get too much sunlight. The plant does this to cut down the area that’s losing moisture and to avoid getting sunburnt. Many plants have this same defense strategy.

Getting too much sun is common for dahlias that are outside or very close to a window. Also, plants that are newly planted tend to be more sensitive to direct sunlight.

Here’s what you can do:

  1. Shift your dahlia to a spot with less sun, but not full shade. Aim for about 6 hours of direct sunlight each day.
  2. If it’s really sunny, water the plant a bit more.
  3. For newly planted dahlias, start them in a place with just 1-2 hours of direct sun.
  4. Gradually get them used to more light.