[The Knotweeds and Smartweeds of the Columbia River Gorge]

Wiry Knotweed, Palouse Knotweed

Polygonum majus

Synonyms: Polygonum coarctatum var. majus, Polygonum douglasii ssp. majus

Inflorrescence of Wiry Knotweed, Palouse Knotweed: Polygonum majus (Synonym: Polygonum coarctatum var. majus, Polygonum douglasii ssp. majus)

The photo above shows the inflorescence of wiry knotweed as seen from a sandy to rocky soils at Horsethief Butte to the northeast of The Dalles, OR................October 7, 2006.

Characteristics:

Wiry knotweed is an upright annual with simple to branched stems afrom 10-30 cm tall. The stems are strongly angled, and the numerous leaves are found on the stems. The leaves are linear to oblong, mostly 2-5 cm long and 2-7 mm wide, sessile, and reduced in size upwards on the stem. The stipules are 10-15 mm long.

The flowers are mostly paired in the elongate racemes. They are in the axils of the upper, reduced bracts. The flowers are about 4-5 mm long, greenish-white with white or pink margins. There are 8 stamens, with puple anthers.


Habitat:

Wiry knotweed may be found on dry gravelly or heavy soils from the sagebrush desert to mountainous ponderosa forests.


Range:

Wiry knotweed may be found east of the Cascade Mts. from northern Washington south to northern California, and east to Idaho and western Montana.

In the Columbia River Gorge, it may be found from east of Mosier, OR to the eastern end of the gorge. It may be found there between the elevations of 100'-600'.


Flower of Wiry Knotweed, Palouse Knotweed: Polygonum majus (Synonym: Polygonum coarctatum var. majus, Polygonum douglasii ssp. majus)
The photo above shows a close-up of the flower of wiry knotweed as seen in sandy soils along Washington SR 14 about 5 miles east of the mouth of the John Day River.....................September 29, 2007. Note the narrow, subtending bract which is much longer than the flower in this case.

Wiry Knotweed, Palouse Knotweed: Polygonum majus (Synonym: Polygonum coarctatum var. majus, Polygonum douglasii ssp. majus)

The complex, branched form of wiry knotweed as seen at Horsethief Butte...................October 7, 2006.

Inflorescence of Wiry Knotweed, Palouse Knotweed: Polygonum majus (Synonym: Polygonum coarctatum var. majus, Polygonum douglasii ssp. majus)

Another close-up of the inflorescence of wiry knotweed as seen at Horsethief Butte.................October 7, 2006.

Paul Slichter