Can I trim back the leggy stems?

Yes, you can prune the long stems to encourage the plant to branch out. It will help the plant look fuller over time.

Does it need fertilizer?

Prostrate knotweed is very hardy and rarely needs fertilizer. It prefers lean soil.

Prostrate knotweed: leggy growth, causes and fixes

Check these first

Observe how many hours of direct sunlight the plant receives.
Check if nearby plants or structures are casting shade on your knotweed.
Look at the soil to see if you have recently added high nitrogen compost.

Likely causes

Insufficient Light
Most likely
How to tell: The stems look long and thin with large gaps between the leaves. The plant leans heavily toward the nearest light source.
What to do: Move the plant to a spot that receives at least 6 to 8 hours of direct sun daily. If it is in a container, relocate it to a brighter area immediately.
Excessive Nitrogen
Possible
How to tell: The plant grows very fast but the stems are weak and floppy. The foliage is a deep, dark green but lacks the typical dense structure.
What to do: Stop using high nitrogen fertilizers immediately. Switch to a balanced, low strength fertilizer or stop feeding entirely for the rest of the season.

Leggy growth in other plants

Find out what's wrong with your prostrate knotweed

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

If the stems are so weak they cannot support themselves, the plant is struggling. It is normal for the plant to grow slightly faster in early spring, but it should remain low to the ground.

Stopping it coming back

Plant in full sun and avoid over fertilizing. Let the plant grow in its natural, low profile environment.

Prostrate knotweed: leggy growth? Check yours with a photo

Every plant is a little different. Take a photo of your prostrate knotweed 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

Can I trim back the leggy stems?: Yes, you can prune the long stems to encourage the plant to branch out. It will help the plant look fuller over time.
Does it need fertilizer?: Prostrate knotweed is very hardy and rarely needs fertilizer. It prefers lean soil.

Why is my prostrate knotweed growing so leggy?