Giant knotweed (Fallopia sachalinensis)

Giant knotweed Synonyms: Polygonum sachalinense, Reynoutria sachalinensis

Common Names: Sakhalin knotweed, Japanese bamboo

Description: Hybridizes with Japanese knotweed and silver lace vine (P. baldschuanicum).

Habit: Perennial, herbaceous shrub reaching 4 m (12 ft); larger than many woody shrubs; stems die back to the ground each year.

Leaves: Simple, alternate, large, 15-30 cm (6-12 in) long and 2/3 as wide with a shallow, heart-shaped base.

Stems: Upright; round; hollow with swollen nodes; resemble bamboo shoots.

Flowers: Sparse, greenish in color, borne on a slender stalk, arise from the leaf axils and stem tips; blooms August through September.

Fruit and seeds: Fruits are three winged, seeds are dark and glossy, wind and water dispersed.

Habitat: Native to Asia, now found along roadsides, stream and river banks, wetlands, wet depressions and woodland edges; shade intolerant; can tolerate a wide array of soil and moisture conditions.

Reproduction: Spreads extensively through rhizomes or fragments; can provide pollen to related species to produce viable hybrid seed.

Similar species: Non-native Japanese knotweed (Fallopia japonica) is smaller (< 6 in long) and its leaves have a flat base, rather than rounded basal lobes.

Monitoring and rapid response: Monitor sunny open sites along paths, ditches and canals. This species is difficult to control research control options thoroughly, particularly for mechanical control methods. On riparian sites, consider upstream and downstream populations and herbicide impacts. Multiple control strategies may be needed for a single population. Resprouts vigorously after cutting, mowing, tilling and digging. Tiny fragments of roots and stem nodes can sprout and form new colonies remove all cut plant materials and incinerate or place in landfill. Foliar herbicide application may provide effective control. Cutting or spraying early in the season and then spraying later may be easiest as plants will still be short enough to spray efficiently. Wicking or injecting herbicide may be suitable for ecologically sensitive sites but is labor intensive. Follow-up required for years.

Credits: The Michigan Natural Features Inventory (MNFI) has partnered with MISIN to provide the information in this fact sheet. Species images and/or information were used with permission from "A Field Identification Guide to Invasive Plants in Michigan's Natural Communities" and "A Field Guide to Invasive Plants of Aquatic and Wetland Habitats for Michigan.


Common Name:

Giant knotweed

Scientific Name:

Fallopia sachalinensis

Family:

Polygonaceae
(Buckwheat)

Duration:

Perennial

Habit:

Herbs

USDA Symbol:

FASA3