Polygonum shastense

Polygonum shastense
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Order:	Caryophyllales
Family:	Polygonaceae
Genus:	Polygonum
Species:	P. shastense
Binomial name
	Polygonum shastense; W.H.Brewer 1872

Polygonum shastense is a species of flowering plant in the knotweed family known by the common name Shasta knotweed. It is native to sections of southwestern Oregon, northwestern Nevada, and northern and central California,^[1] where it grows in rocky and gravelly mountainous habitat up to 3300 meters (11,000 feet) elevation.^[2] It is most common in the Sierra Nevada.^[3] The species name refers to its occurrence on Mount Shasta in Shasta County, California.^[4]

Description

Polygonum shastense is a rather elegant small perennial shrub producing branching tough, gnarled brown stems reaching a maximum length of 40 centimeters (16 inches), growing prostrate along the ground or somewhat upright. The bases of old plants can be wide, woody and gray (see image above left).^[5]

The leaves lining the slender but rough stems are uniform in size and distribution, not clustered or reduced in size near stem tips. They are lance-shaped with two parallel veins separating three raised areas on the upper surface (see closeup at left), each leaf measuring 5 to 8 millimeters (0.20–0.32 inches) long.^[2] Leaves emerge curled slightly and folded in half lengthwise. Leaves have stipules which are widened into membranous ochrea wrapped around the leaf bases.^[5]

Flowers occur in clusters in upper leaf axils. Each is just under a centimeter wide and has five rounded petals, either white with a green stripe or pink with a dark stripe. There are 5–8 stamens and a triangular pistil with a 3-lobed style. Plants may have either all white, all pink, or a mixture of flower colors.^[5]