Pocket Botanist
Check these first
- Feel the soil 2 inches down to see if it is soggy.
- Check the drainage holes to ensure they are not blocked.
- Smell the soil for any signs of decay.
Likely causes
Overwatering
Most likelyHow to tell: The leaves turn yellow or wilt even though the soil feels wet. You might notice a sour smell coming from the pot.
What to do: Stop watering immediately and let the top 2 inches of soil dry out. If the plant does not recover in a few days, gently remove it from the pot to inspect the roots for mushy or black sections.
Poor Drainage
PossibleHow to tell: Water sits on the surface of the soil for a long time after you water. The pot lacks holes or the drainage tray stays full of water.
What to do: Ensure your pot has drainage holes at the bottom. Empty the saucer after every watering so the roots are not sitting in standing water.
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
If the stems feel soft or mushy at the base, the plant is likely too far gone to save. It is normal for a few lower leaves to drop if the plant is adjusting to a new spot.
Stopping it coming back
Always use a well draining potting mix and wait until the top inch of soil is dry before watering again.
Knotweed: root rot? 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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Or go to pocketbotanist.app/get on your phone
Get the app · Or check it from a photo now, free
Questions people ask
- Can I save a plant with root rot?
- Yes, if you catch it early. Trim away the black, mushy roots with clean scissors and repot the plant in fresh, dry soil.
- How often should I water my Persicaria?
- Check it every 3 to 7 days. Only water when the top inch of soil feels dry to the touch.
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.