''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 Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

, northwestern

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

, and northern and central

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

, where it grows in rocky and gravelly mountainous habitat up to 3300 meters (11,000 feet) elevation. It is most common in the Sierra Nevada. The species name refers to its occurrence on

Mount Shasta Mount Shasta ( Shasta: ''Waka-nunee-Tuki-wuki''; Karuk: ''Úytaahkoo'') is a potentially active volcano at the southern end of the Cascade Range in Siskiyou County, California. At an elevation of , it is the second-highest peak in the Cascades ...

in Shasta County, California.Brewer, William Henry. 1872. Proceedings of the American Academy of Arts and Sciences 8: 400, in footnote
/ref>

Description

''Polygonum shastense'' is a rather elegant small perennial

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...

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). 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. Leaves emerge curled slightly and folded in half lengthwise. Leaves have stipules which are widened into membranous

ochrea An ochrea (Latin ''ocrea'', greave or protective legging), also spelled ocrea, is a plant structure formed of stipules fused into a sheath surrounding the stem, and is typically found in the Polygonaceae The Polygonaceae are a family of flower ...

wrapped around the leaf bases. 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.Flora of North America, ''Polygonum shastense'' W. H. Brewer, 1872. Shasta knotweed
/ref>

References

External links

Jepson Manual Treatment – ''Polygonum shastense''''Polygonum shastense'' – Calphotos Photo gallery, University of California
{{Taxonbar, from=Q7226471 shastense Flora of California Flora of Nevada Flora of Oregon Flora of the Sierra Nevada (United States) Endemic flora of the United States Plants described in 1872 Taxa named by Asa Gray Flora without expected TNC conservation status