Polygonum sachalinense (Giant knotweed)

Polygonum sachalinense F. Schmidt ex Maxim.

Giant knotweed, Sakhalin knotweed, Japanese bamboo

Kingdom	Plantae	Plants, but not fungi, lichens, or algae
Subkingdom	Tracheobionta	Vascular plants—plants with a “circulatory system” for delivering water and nutrients
Division	Magnoliophyta	Flowering plants, also known as angiosperms
Class	Magnoliopsida	Dicotyledons—plants with two initial seed leaves
Subclass	Caryophyllidae	Cacti, many other succulents, carnivorous plants, and leadworts
Order	Caryophyllales	Includes cacti, carnations, amaranths, ice plants, and many carnivorous plants
Family	Polygonaceae	Knotweed or smartweed family
Genus	Polygonum	Greek poly, “many,” and gonu, “knee,” for the swollen jointed stems
Species	sachalinense	From the Sakhalin Islands north of Japan

About plant names...

Giant knotweed is related to the more common and smaller Japanese knotweed. It is Asian in origin, introduced to North America as an ornamental plant. Both knotweeds spread rapidly, and are considered invasive species.

Identification: Giant knotweed favors rivers, swamps, and other wetland regions. They spread via their root systems, which may extend 50 feet or more and have roots up to 3" (7.6 cm) in diameter. Stems are hollow, and thickly clustered, closely resembling bamboo. Plants reach 13' (4 m) in height. Leaves are alternate, ovate (oval, wider at the bottom), cordate (heart-shaped), up to 12" (30 cm) long, with crenate (wavy) edges. Flowers are groups of slender cone-shaped panicles, white or greenish in color, appearing from July to October.

7/17/2010 · Mackworth Island, Falmouth, Maine
≈ 16 × 24" (41 × 62 cm)

These plants are about 10' high. · 7/17/2010 · Mackworth Island, Falmouth, Maine
≈ 3½ × 2½' (1.2 × 0.8 m)

Here is a comparison between giant knotweed and Japanese knotweed:

	You are here Polygonum sachalinense	*Polygonum cuspidatum*
Common Name	giant knotweed	Japanese knotweed
Plant	Stems are hollow, and thickly clustered, closely resembling bamboo. Plants are *large*, up to 13' (4 m) in height.	Japanese knotweed stems are jointed and hollow like bamboo. Plants reach up to 12' (3.7 m), but are usually *half that*.
Flowers	Groups of slender cone-shaped panicles, white or greenish in color.	In multiple upward pointing spikes containing many tiny white to pale yellow flowers.
Leaves	Alternate, ovate (oval, wider at the bottom), cordate (*heart-shaped), up to 12" (30 cm) long, with crenate (wavy*) edges.	Leaves are oval, wider and *flat* near the base, 2-6" (5-15 cm) long and 1-4" (2.5-10 cm) wide.
Fruit	Triangular, with three “wings.”	Seed pods are shaped like inverted hearts, about ⅛" (3.2 mm) long.
Range/ Zones	USDA Zones: 5-8
Habitats	Rivers, swamps, and other wetland regions.	Wet areas and disturbed areas
Type	Wild	Wild

Online References:

Polygonum sachalinense on Discover Life

Polygonum sachalinense on the King County Washington Noxious Weeds list

Polygonum sachalinense on Wikipedia

Polygonum sachalinense on the USDA Forest Service's Fire Effects Information Database

Polygonum sachalinense on the USDA Plants Database

Polygonum sachalinense on CalPhotos

Polygonum sachalinense on Plants for a Future, a resource and information centre for edible and otherwise useful plants

Fallopia sachalinensis (F. Schmidt ex Maxim.) Ronse Decr.

Reynoutria sachalinensis (F. Schmidt ex Maxim.) Nakai

Polygonum sachalinense description by Thomas H. Kent, last updated 15 Jul 2020.

Range: Zones 5-8:

About this map...