⚠️ Invasive - DO NOT CUT
Japanese Knotweed
Fallopia japonica
⚠️ WARNING: While this plant is invasive, DO NOT attempt to remove it. Even small fragments can spread and cause more damage.
Fallopia japonica
⚠️ WARNING: While this plant is invasive, DO NOT attempt to remove it. Even small fragments can spread and cause more damage.
A fast-growing, bamboo-like plant with hollow stems and heart-shaped leaves. It spreads aggressively along riverbanks, trails, and disturbed areas. Extremely difficult to control — even a fragment of stem or root can establish a new colony.
Colour and texture: Bright green, up to six inches long, alternating in a distinct zigzag along a hollow cane mottled reddish-purple, with a papery sheath at each joint.
Flowers August–September.
Sprays of tiny creamy-white flowers in loose plumes from the leaf joints, later small winged brown seeds.
Why it matters: Here it spreads almost entirely by root and stem fragments rather than seed, which is exactly why the answer is never to cut it.
Japanese knotweed and anything else tagged DO NOT CUT. The correct action here is not a gentler removal. It is no removal.
Avoid: Do not cut it "just to knock it back", and do not put any part of it in a brush pile, compost heap or yard-waste bin.
Why volunteers never treat it: cutting makes it grow back harder and spreads fragments. Controlling a stand is the landowner's decision, carried out by a licensed applicator:
• into the hollow canes, which keeps herbicide out of nearby water • in late summer and early fall, when it works best • only as part of a managed program, every 2–3 weeks over several seasons
Bag it, and stop. Do not cut any more of it. Bag the pieces already cut and put them in household trash. Never a brush pile, never compost, never the green-waste bin. Everything still rooted stays exactly where it stands.
Someone has already cut, mown, strimmed, pulled or dug a knotweed patch, or soil, mulch or fill has been moved off one. A patch nobody has touched is not an emergency: mark it, report it, walk on.
Your part is the one above: leave it, mark it, and tell your host.
Your host, then the party coordinator
Always first, and usually the only call a volunteer makes. They hold the relationship with whoever owns the ground and they decide what happens next.
The landowner or land manager
City park, county, state land, a land trust or a private owner. Treatment on their land has to be their decision. Your coordinator knows which one it is.
Your state’s Cooperative Extension service
The free public advice line for "we have a stand of this, now what". Every state has one attached to its land-grant university; in Maryland it is the University of Maryland Extension. Ask for the invasive plants or home-and-garden desk.
A licensed invasive-species contractor or pesticide applicator
Only the landowner or the coordinator arranges this. Knotweed is controlled by stem injection or foliar treatment in late summer by someone licensed to do it. Near water that licence matters legally, not just practically.