Bohemian knotweed (Fallopia × bohemica) is a fertile hybrid between two highly invasive plants, Japanese knotweed and giant knotweed, and it shares features of both of those plants. The hybrid was introduced into North American and cultivated as an ornamental. It escaped from cultivation and is now naturalized across northern United States. It is reported to be partially or fully fertile, but it spreads mostly by rhizomes and by the dispersal of plant fragments.
Bohemian knotweed is found on river banks, along roadways, and in other disturbed areas. It often forms large dense colonies. Its bamboo-like stems are erect, stiff, and hollow, and usually have many long slender branches. The leaves are up to 12″ long and may be spade-shaped, straight across at the base, or slightly heart-shaped, indented at the base. Both leaf shapes may appear on the same branch. Flowers appear from July to October. The inflorescence may be long, narrow, and unbranched, or short, broad, branched, and plume-like, and it may be either shorter or longer than the nearest leaf.
Though one parent, Japanese knotweed, is listed as invasive in Minnesota, this hybrid is not … yet.