Japanese Knotweed (Fallopia japonica)

Download 211K pdf file ("japanese_knotweed.pdf")PDF
     Subscribe to our free E-Newsletter, "Agri-News" (formerly RTW This Week)Agri-News
This Week
  Return to the Weed Information Home Page
Plant can reach up to 2-3 m tall, often forming dense thickets. Upright bamboo-like stems with long spikes of small white flowers very numerous along the branches. Leaves cut off square at broad base, continuing broad for most of their length and then curving in to pointed tip. Stems usually reddish and zig zag. Has a distinctive rhizome (root) system, which often extents to approximately 7 m horizontally from the parent plant and approximately 3 m vertically in depth below the parent plant.

Key Identifiers
  • Bamboo like stems
  • Often forms extensive rhizomatous root system colonies.
  • Leaves can reach 3-10 cm in length, with distinct straight leaf base
  • Leaves arranged in a zigzag pattern along the stem.
  • Distinctive orange centered rhizome (root).
  • Hairs on the leaf undersides especially along the midvein are reduced to barely noticeable bumps. These hairs are easiest to see with a hand lens during the spring and summer, often falling off later in the season.
  • Flower clusters are generally longer in length as the below leaf. Leaf and flower characters are most reliable when looking near the middle of a branch.
Location in Canada
BC, MB, Ontario, Quebec and eastern Canada all report the presence of Japanese Knotweed. Alberta is suspected to have a few ornamental locations of unconfirmed knotweed.


Richard Old, XID Services, Inc., Bugwood.org

Steve Manning, Invasive Plant Control, Bugwood.org

Similar species
Giant Knotweed (F. sachalinensis) can be distinguished by the leaves, which are usually 20-40 cm, deeply indented at the base, leaf tip pointed, leaf texture thin and flexible.

Hybrid Japanese Knotweed (F x bohemica) can be distinguished by the leaves, which are usually 5-30 cm, variable at the base, leaf tip variably pointed, leaf texture intermediate.

Elderberries (Sambucus spp.) have lance-shaped, pointed, and sharply toothed leaflets.

Other Documents in the Series

  Bighead Knapweed (Centaurea macrocephala)
Black Knapweed (Centaurea nigra)
Brown Knapweed (Centaurea jacea)
Common Crupina (Crupina vulgaris)
Common St John's-wort (Hypericum perfoatum)
Diffuse Knapweed (Centaurea diffusa)
Dyer's Woad (Isatis tinctoria)
Garlic Mustard (Alliaria petiolata)
Giant Hogweed (Heracleum mantegazzianum)
Giant Knotweed (Fallopia sachalinensis)
Hoary Alyssum (Berteroa incana)
Hybrid Japanese Knotweed (Fallopia x bohemica)
Hybrid Knapweed (Centaurea x psammogena)
Japanese Knotweed (Fallopia japonica) - Current Document
Marsh Thistle (Cirsium palustre)
Meadow Hawkweed (Hieracium caespitosum)
Meadow Knapweed (Centaurea x moncktonii)
Mouse-ear Hawkweed (Hieracium pilosella)
Nodding Thistle (Carduus nutans)
Plumeless Thistle (Carduus acanthoides)
Puncturevine (Tribulus terrestris)
Red Bartsia (Odontites vernus)
Rush Skeletonweed (Chondrilla juncea)
Russian Knapweed (Rhaponticum repens)
Saltlover (Halogeton glomeratus)
Spotted Knapweed (Centaurea stobe ssp. micranthos)
Squarrose Knapweed (Centaurea virgata ssp. squarrosa)
Sulphur Cinquefoil (Potentilla recta)
Tansy Ragwort (Jacobaea vulgaris/Senecio jacobaea)
Tyrol Knapweed (Centaurea nigrescens)
Yellow Starthistle (Centaurea solstitialis)
Share via AddThis.com
For more information about the content of this document, contact Chris Neeser.
This document is maintained by Shelley Barkley.
This information published to the web on April 10, 2012.
Last Reviewed/Revised on August 21, 2018.