Polygonum cuspidatum (Japanese knotweed)

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Polygonum cuspidatum Siebold & Zucc.

Japanese knotweed, Mexican 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	cuspidatum	“Tipped with a firm point”

About plant names...

Another story of a good plant gone bad. Japanese knotweed is a native of Japan, China, and Korea. Introduced to Europe and North America as an ornamental plant, it has been so successful that it is considered one of the 100 worst invasive species. Fast-growing root systems form dense hedges that crowd out other species.

Identification: Japanese knotweed stems are jointed and hollow like bamboo. Thin branches are reddish. Plants reach up to 12' (3.7 m). Flowers appear in multiple upward pointing spikes containing many tiny white to pale yellow flowers. Leaves are oval, wider near the base, 2-6" (5-15 cm) long and 1-4" (2.5-10 cm) wide. Seed pods are shaped like inverted hearts, about ⅛" (3.2 mm) long. The plants favor wet areas and disturbed areas.

7/27/2016 · Michaux State Forest, Caledonia State Park, Fayetteville, Pennsylvania
≈ 10 × 15" (26 × 37 cm)

10/20/2013 · Barrett Park, Leominster, Massachusetts
≈ 7 × 5" (16 × 12 cm)

Here is a comparison between giant knotweed and Japanese knotweed:

	*Polygonum sachalinense*	You are here 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

Medical: Historically, extracts from Japanese knotweed have been used to treat menstrual cramps and postpartum depression. Other ingredients aid in treatment of burns; these are also used in skin lotions. There are many other purported but unconfirmed health benefits.

Edibility: Thicker young shoots, gathered early in the spring, can be cooked in boiling water or a steamer and served with butter, like asparagus. And like asparagus, they cook quickly, and should be served as soon as they are easily pricked with a fork. See herbalpedia.

Online References:

Wikipedia

The Washington State Department of Ecology

Www.ag.purdue.edu (PDF)

Invasive.org, Center for Invasive Species and Ecosystem Health

The Virginia Tech Weed Identification Guide

CalPhotos

Klemow.wilkes.edu (a technical summary of the medical properties)