As you can see in the picture, one of my Dahlia plants is showing curling leaves. There might be multiple reasons behind this. In this article, I will talk about the major reasons why Dahlia leaves curling and how to treat it.
Note: Dahlia do the best in USDA Zone 8-11. An excessive amount of nitrogen may not be good for Dahlia plants. Excessive heat and cold both can affect this plant. They can easily get caught by aphids and other pests in warmer regions.
Why did I tell these? Wait! you will get to know.
3 Reasons why Dahlia leaves curling
These are the 3 major reasons:
- Overfertilization or not maintaining the proper ratio.
- Unusual environment (Maybe extreme heat or extreme cold)
- Pest attacks (mostly aphids)
There are a few other reasons like draught, salt-water damage, and wind damage. I will not go deep into those. Let's talk about the major reasons.
Overfertilization or not maintaining the proper nutrition ratio
It's best to use balanced fertilizer in the early stage, and when you notice small buds increase the phosphorus ratio.
If you keep pushing nitrogen-based fertilizers (especially urea), your Dahlia plant might go bushy or show curly leaves.
Due to over-fertilization or imbalanced fertilizer, you can also notice black spots on the leaves.
If you have already fertilized recently, water thoroughly for the next few days. (Make sure that water is draining properly). It will wash off the fertilizers.
Unusual environment
As I told you at the beginning of this article, excessive heat and cold both can affect this plant.
This is my personal experience:
I grow Dahlias in Zone 10 which is a warmer region. But at the end of the blooming season when the heat rises, I have to see a lot of curly leaves on my Dahlia plants.
I do not worry much as I know this is due to the heat increase. If you still want to protect your Dahlia from the heat, give shade clothes when the sun is above your head.
Gardeners growing Dahlia in colder regions ( Zone 8 or Lower), can see the curly leaves when the weather suddenly turns cold.
You need to worry when the new leaves are curly just like this:
Pest attacks (mostly aphids)
The aphids love to suck the juice (Sap) from the green stalks of the Dahlia plants. (Mostly the top new growths)
Due to this, the leaves turn curly. You can find them on the stems as well as under the leaves.
You can check this guide: Get rid of aphids on mums ( The treatment will work on the Dahlia plant in the same way)
If you find mealybugs, this is for you: get rid of mealybugs - My tested methods
Do not let the soil completely dry for more than 2 days. If you have experienced heavy winds or hurricanes in your area recently check: wind-burn damage prevention and Salt-water damage prevention.
Here is a bonus tutorial for you if you are a Dahlia grower: Why do Dahlia change colors on the same plant
