Probably not. Japanese knotweed is very hard to kill and usually recovers quickly once the soil moisture is corrected.

Should I cut off the yellow leaves?

Yes, you can trim them off to keep the plant looking tidy.

Japanese knotweed: yellow leaves, causes and fixes

Check these first

Stick your finger two inches into the soil to check for dampness.
Look for signs of standing water around the base of the plant.
Check if the yellowing is concentrated on the oldest leaves.

Likely causes

Overwatering
Most likely
How to tell: The soil feels soggy or swampy to the touch. The yellowing often starts on the lower leaves first.
What to do: Let the soil dry out completely between waterings. Since this plant is drought tolerant, you only need to water every 7 to 14 days.
Nutrient Deficiency
Possible
How to tell: The leaves turn a pale, uniform yellow, often starting with the older growth. This happens if the soil has been depleted of nutrients over several seasons.
What to do: Apply a balanced, slow release fertilizer once in the early spring. Do not overdo it, as this plant is very efficient at gathering nutrients.

Yellow leaves on other plants

Find out what's wrong with your japanese 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

It is normal for a few old leaves to yellow and drop in late summer. Worry if the yellowing is rapid and affects the entire plant.

Stopping it coming back

Ensure the soil has good drainage and avoid keeping the roots constantly wet.

Japanese knotweed: yellow leaves? Check yours with a photo

Every plant is a little different. Take a photo of your japanese 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

Is my plant dying?: Probably not. Japanese knotweed is very hard to kill and usually recovers quickly once the soil moisture is corrected.
Should I cut off the yellow leaves?: Yes, you can trim them off to keep the plant looking tidy.

Why are the leaves on my Japanese knotweed turning yellow?