|Fallopia subsp. var.|
Fallopia is a genus of about 12–15 species of flowering plants in the family Polygonaceae, often included in a wider treatment of the related genus Polygonum in the past. The genus is native to temperate and subtropical regions of the Northern Hemisphere. The genus includes herbaceous perennial plants, herbaceous vines, and woody vines.
Many knotweed species, particularly Japanese knotweed, giant knotweed and Himalayan knotweed are considered noxious, invasive pests. Like many such weeds, Japanese knotweed was introduced from Japan first into the U.K., then into North America in the 19th century as an ornamental plant.
Some knotweeds grow extremely quickly during the spring; giant knotweed can reach 4.5 m by summer, Japanese knotweed 3 m, and "dwarf" Himalayan knotweed 1.5–2 m. In Japan, Japanese knotweed is known as itadori, or "strong plant". Some species can spread rapidly from an extensive network of rhizomes (roots that can sprout) spreading from 7–20 m from the parent plant and at least 2 m deep. Root and stem fragments as small as 1 cm can form new plant colonies. Floods and high water events wash whole or partial plants into rivers and creeks, dispersing pieces of knotweed throughout the flooded area and banks, which give rise to new plants. As with other invasive species of plants, freshly disturbed soil allows the rapidly growing young knotweed plants to outgrow other plants and take over the area, suppressing other species. Cutting, mowing, digging and some herbicide treatments, especially in early to mid growing season, fail to curb knotweed growth and in fact often stimulate the production of shoots from latent buds dispersed on the root crown or rhizomes.
Pests and diseases
- Fallopia baldschuanica Russian vine; mile-a-minute vine; China fleece vine; fleece flower; silver lace vine (syn. Fallopia aubertii, Polygonum baldschuanicum, Polygonum aubertii). Eastern Asia.
- Fallopia cilinodis fringed black bindweed (syn. Polygonum cilinode, Bilderdykia cilinodis). North America.
- Fallopia convolvulus Black-bindweed (syn. Polygonum convolvulus, Bilderdykia convolvulus). Europe, Asia, northern Africa.
- F. convolvulus var. subalatum
- Fallopia cynanchoides (syn. Polygonum cynanchoides). Western China.
- Fallopia dentatoalata (syn. Polygonum dentatoalatum). Eastern Asia.
- Fallopia denticulata (syn. Polygonum denticulatum). Southern China.
- Fallopia dumetorum copse bindweed (syn. Polygonum dumetorum, Bilderdykia dumetorum). Europe, Asia, northern Africa.
- Fallopia forbesii (syn. Polygonum forbesii). Northern China, Korea.
- Fallopia japonica Japanese knotweed (syn. Polygonum cuspidatum, Polygonum japonicum, Polygonum reynoutria, Reynoutria japonica). Eastern Asia.
- F.japonica var. compacta
- F.japonica var. compacta f. rosea Hort.
- Fallopia multiflora (syn. Polygonum multiflorum). Eastern Asia.
- F. multiflora var. hypoleuca
- Fallopia polystachyum.
- Fallopia pterocarpa (syn. Polygonum pterocarpum). Southern Asia.
- Fallopia sachalinensis giant knotweed (syn. Polygonum sachalinense, Reynoutria sachalinensis). Eastern Siberia.
- Fallopia scandens. North America.
Hybrids: Crosses between Japanese knotweed and giant knotweed have occurred where the two species grow in close proximity. The hybrid, Fallopia × bohemica (syn. Polygonum × bohemicum) is known as Bohemian knotweed.
Fallopia × conollyana (F. baldschuanica × F. japonica) is called railway-yard knotweed.