Dahlia Leaves Curling (Causes and Solutions)

Dahlia is different from many other flowers because of the large number of petals that create unique patterned flowers. So it’s not surprising that many people want to have this beautiful plant in their gardens or homes. But like other plants with Dahlia, some problems can arise.

Underwatering, dry air, various pests, or diseases are the main reasons for dahlia leaves curling. To fix curled leaves you need to water the dahlia as soon as the soil is 1 inch dry, make sure it is placed away from heaters. Also, treat the plant with horticultural oil and an aqueous fungicide solution.

Temperature stress can cause dahlia leaves curling

One of the most common causes of curling dahlia leaves is temperature stress. This plant rarely experiences low temperatures in its native environment, which is the reason why dahlia is mostly grown as an indoor plant in colder climates. If for any reason the plant is overcooled, curling of the leaves is one of the possible symptoms.

Not only cold but also heat can affect the shape of dahlia leaves. If it has been very hot indoors or outdoors, the leaves may curl down or even wilt.

Symptoms:

• Leaves curl with the tips downward.
• The leaves are deformed and change color.
• The plant is placed in a location where the temperature drops below 50°F (10°C).

Solution:

• Provide dahlia at 60-95°F (15-35°C).
• Avoid growing the dahlia in a location where temperatures can exceed 100°F (38°C).
• Do not place dahlia close to heating or cooling devices.
• Avoid placing the dahlia in a place where there are cold drafts.

Underwatering

Dahlia is absolutely not a drought-tolerant plant. The large leaves of this plant evaporate a lot of moisture every day. As a result, the dahlia needs constant water replenishment.

Usually, the air in the room is drier than outdoors and the potting soil dries out faster. This can lead to dehydration and curling of the leaves.

To find out if the dahlia needs water, check the soil moisture and if it is 1 inch dry, it is time to water.

Be careful not to water the dahlia too often to avoid root rot. This is the reason for using drained soil and pots with holes in the bottom.

Symptoms:

• The leaves of the dahlia curl down or droop.
• The leaf tips turn brown.
• The potting soil is dry.

Solution:

• Water the dahlia when the soil is 1 inch dry.
• Use plenty of water when watering, and let the excess come out through the drainage holes.
• Do not overwater the dahlia as this will lead to root rot.

Pests

Insects are the next possible cause of curling dahlia leaves. In fact, there are many pests that can damage this plant, but the most common are aphids, mealybugs, thrips, and scale insects. They all stick to the leaves and feed on the sap of the plant. As a result, the leaves twist and deform.

Spider mites are worth a special mention. These are very tiny bugs that can only be seen with a magnifying glass. They also feed on the sap of the dahlia and cause the leaves to curl.

Symptoms:

• The leaves of the dahlia curl up.
• Deformations and tubercles can be seen on the leaves.
• Small insects and spider webs can be seen on the plant.

Solution:

• Examine the plant carefully, using a magnifying glass to look for mites.
• If you find aphids, mealybugs, thrips, or scale insects, wash them off with water and after a day or two, spray the plant with an aqueous solution of horticultural oil.
• If there are mites on the leaves, use acaricide to get rid of them.

Lack of sunlight

Dahlia leaves curling due to a lack of light.The downward curling of the leaves of the dahlia is usually due to an insufficient amount of direct sunlight. In fact, this is a common problem because there is relatively little direct sunlight indoors.

If your dahlia gets little or no direct sun, sooner or later it will stretch out. Growth will come at the expense of internal energy reserves, which will greatly weaken the plant. As a result, the leaves will not only curl down but will be more susceptible to fungal diseases.

Symptoms:

• Dahlia’s leaves curl downward.
• Leaves and the whole plant becomes elongated.
• The dahlia becomes weak and slows its growth.

Solution:

• Provide the dahlia with at least 6 hours of direct sunlight. This can be achieved by placing it in front of a south-facing window.
• Introduce the dahlia to more light gradually. Add 1 hour of sunshine per week.
• If you don’t have a place with the right amount of light, install artificial light.

Diseases

Root rot is the most unpleasant disease of the dahlia because it is difficult to detect in its first stage. Usually the leaves start to curl and turn yellow when some of the roots have rotted. In this case, you must treat the dahlia immediately so that you do not lose it.

Fungal diseases such as Leaf spot or mold can also affect the leaves of the dahlia and they will turn yellow or brown. In this case the plant also needs immediate treatment.

Symptoms:

• Dahlia leaves turn yellow and curl inward from root rot.
• Leaves are deformed erratically and have brown spots or mold on them.
• The soil in the pot is too moist.

Solution:

• If root rot is the cause of the curling, pull the plants out of the pot and clean and wash them. Then remove the rotten part and treat the wounds with a 10% aqueous hydrogen peroxide solution.
• Plant the dahlia in clean, drained soil. The pot should have holes in the bottom.
• Allow the soil to dry 1 inch between watering the dahlia.
• If the curling was caused by a fungal disease, remove the damaged leaves and spray the plant with a copper-based fungicide.
• Provide the dahlia with good air exchange.

Nutrients

To create large flowers full of seeds, the dahlia needs a lot of nutrients. In the first years, the plant uses nutrients from the soil, but when the soil is depleted there is a fertilizer deficiency. One of the symptoms will be curling leaves.

In addition, the dahlia is an annual plant, which means that it needs to regenerate its above-ground part every year. This process also requires a lot of energy. It follows that the dahlia needs a lot of fertilizer every year.

Symptoms:

• Leaves curl and turn yellow.
• The plant slows down a lot.
• The dahlia will not flower.

Solution:

• Fertilize the dahlia in early spring with a slow-release multipurpose fertilizer.
• Make sure the fertilizer contains nitrogen, potassium, and phosphorus.
• Water the dahlia once with liquid fertilizer after flowering.
• Avoid fertilizing the dahlia for the winter.

Harsh sun

Too much sunlight can cause dahlia leaves to curl inward. This happens because the plant is trying to reduce the evaporation area and not to get burned. This defense mechanism is common to many plants.

An overabundance of sunlight usually occurs if the dahlia is growing outside or very close to a windowpane. Also, newly planted plants are more sensitive to direct sun.

Symptoms:

• Dahlia leaves curl and can get burnt.
• The soil in the pot is dry.
• The plant receives more than 10 hours of direct sunlight per day.

Solution:

• Move the dahlia to a less sunny location but not full shade. The plant should get about 6 hours of direct sun per day.
• Increase watering slightly if the sun is blazing.
• Move newly planted plants to a location with 1-2 hours of direct sunlight and accustom them to more light gradually.