Pocket Botanist
Check these first
- Move the plant closer to a bright window.
- Rotate the pot every week to ensure even light exposure.
- Prune back long stems to encourage branching.
Likely causes
Insufficient Light
Most likelyHow to tell: The stems are stretching out with large gaps between the leaves. The plant leans heavily toward the nearest window.
What to do: Move your plant to a spot with brighter, indirect light. If you cannot provide enough natural light, consider using a grow light for 8 to 10 hours a day.
Lack of Pruning
PossibleHow to tell: The plant is tall and sparse but otherwise looks healthy. It has not been trimmed back in a long time.
What to do: Prune back the long, straggly stems by one third to encourage bushier growth. Do this in early spring to help the plant fill out during the growing season.
Find out what's wrong with your 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.
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When to worry
It is normal for the plant to grow slightly taller during the winter months when light levels are lower. You should worry if the stems become so weak they cannot support their own weight.
Stopping it coming back
Provide consistent bright, indirect light and prune the plant lightly each spring to maintain a compact shape.
Knotweed: leggy growth? Check yours with a photo
Every plant is a little different. Take a photo of your 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.
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Questions people ask
- Does this plant flower?
- Yes, Persicaria produces lovely spikes of flowers in the summer. It needs consistent bright light and regular moisture to bloom well.
- Will my leggy stems fill back in?
- The existing stems will not grow leaves where they are currently bare. Pruning them will encourage new, fuller growth from the base.
More problems with Knotweed
This article was generated with AI on from the plant’s care profile and is general information, not horticultural advice. Read about how we build these guides.