Also called Reynoutria japonica and Polygonum cuspidatum.
"Japanese knotweed" may also refer to hybrids of this plant with its very-close sister-species
giant knotweed Reynoutria sachalinensis,
with the hybrids known as
bohemian knotweed Reynoutria × bohemica,
Fallopia × bohemica, and Polygonum × bohemicum.
Part of
buckwheat/knotweed family Polygonaceae.
Native to 🇨🇳 China, 🇰🇵 🇰🇷 Korea, and 🇯🇵 Japan.
Invasive > learn+quiz
Invasive > 🌐︎ global
Invasive > 🌐︎ various
Invasive > USA+Canada
Invasive > report it!
Invasive > USA
Invasive > Michigan
Invasive > Michigan 
(page 57)
Invasive > Michigan (aquatic) (page 53)
prohibited in Michigan, incl. seeds, fragments and derivatives.
Inv. trading card
🚸︎🚼︎ For kids! This plant described in invasive species placemat
series.
Purposely introduced as an ornamental, in North America, 🇪🇺 Europe and 🇦🇺 Australia Japanese Knotweed forms extremely dense monocultures, spreads rapidly by roots, plant fragments, and rhizomes, destroying building foundations, cracking drain pipes, and eroding streambanks. It can grow through
concrete and asphalt.
It also releases
allelopathic chemicals
into the soil
, ☠︎ toxic
to native ecosystems.
Japanese Knotweed is restricted (illegal to possess or introduce) in areas of 🇨🇦 🇺🇸 🇲🇽 North America, 🇪🇺 Europe, and 🇦🇺 Australia.
For full effect, view the three videos
↖ above or to left by selecting the video image, choosing Part 1 then 2 then 3,
then icons
YouTube (if present),
⏯︎ ⊠ Skip Ads (if present),
㏄ captions
(if you wish),
⛶ fullscreen, and ▶︎ Play.
Japanese knotweed is adapted to grow in 🌋︎ volcanic soil — like ⛰ basalt! No wonder it grows through concrete and asphalt!
Uses by native peoples
(Ethnobotany database)
Recipes.
On No-Planting List by Seneca Nation of Indians SNI. (page 61)