Are aphids harmful to my plant?

Yes, they suck the sap from the plant and can stunt its growth. It is best to treat them as soon as you spot them.

Should I cut off the curled leaves?

You can remove severely damaged or distorted leaves to improve the plant's appearance. If the leaf is still green and healthy otherwise, it is fine to leave it.

Perennial sowthistle: curling leaves, causes and fixes

Check these first

Inspect the undersides of the curled leaves for small insects.
Check if the soil is dry to the touch.
Feel the leaves to see if they are brittle or soft.

Likely causes

Aphids
Most likely
How to tell: You will see clusters of tiny green or black insects on the undersides of leaves or along the stems. The leaves may look distorted or puckered.
What to do: Spray the aphids off with a sharp stream of water from your hose. For heavy infestations, apply insecticidal soap every 5 to 7 days until they are gone.
Heat stress
Possible
How to tell: The leaves curl inward during the hottest part of the day to conserve moisture. They usually flatten out again once the temperature drops in the evening.
What to do: Water the plant deeply to ensure the soil is moist but not soggy. Apply a layer of mulch around the base to keep the roots cool.

Curling leaves on other plants

Find out what's wrong with your perennial sowthistle

The list above covers the usual causes. Pocket Botanist looks at a photo of your actual plant and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.

When to worry

Worry if you see sticky residue on the leaves, which indicates a serious aphid problem. Temporary curling during a heatwave is a normal defense mechanism.

Stopping it coming back

Monitor your plant weekly for pests and keep the soil consistently moist to prevent heat stress.

Perennial sowthistle: curling leaves? Check yours with a photo

Every plant is a little different. Take a photo of your perennial sowthistle and Pocket Botanist tells you which cause is most likely, how serious it is, and what to try first. A few checks a day are free. Save the plant and you get care reminders timed for it.

Get the app · Or check it from a photo now, free

Questions people ask

Are aphids harmful to my plant?: Yes, they suck the sap from the plant and can stunt its growth. It is best to treat them as soon as you spot them.
Should I cut off the curled leaves?: You can remove severely damaged or distorted leaves to improve the plant's appearance. If the leaf is still green and healthy otherwise, it is fine to leave it.

Guides to these causes

Aphids

Why are my perennial sowthistle leaves curling?