[Knotweeds and Smartweeds: The Genera Bistorta, Fallopia, Persicaria and Polygonum in the Columbia River Gorge of Oregon and Washington]

Closeflowered Knotweed

Polygonum polygaloides ssp. confertiflorum

Synonyms: Polygonum confertiflorum, Polygonum imbricatum, Polygonum kelloggii var. confertiflorum, Polygonum watsonii

Close-ups of the axillary flowers and white-margined floral bracts of closeflowered knotweed blooming in flat, shallow vernal pools at Catherine Creek, Columbia River Gorge.......June 21, 2001.

Characteristics:

Closeflowered knotweed is a small annual, smooth-surfaced with a simple or many-branched stem from 6-20 cm high. The leaves are linear (See photos.), 1-3 cm long and 1-2 mm wide. The flowers are 2-4 per node in crowded clusters at the ends of the branches, or occasionally in the axils of the leaves. The leaves become reduced to small bracts near the ends of the branches. The terminal bracts are distinctly white-margined (See photo below.).

The flowers are 1.5-2.5 mm long with greenish midstripe and white to pinkish borders. There are 8 stamens, with the 3 inner ones bearing anthers, the other 5 without anthers. Closeflowered knotweed is very similar to (and probably closely related) Kellogg's knotweed (Polygonum kellogii) but may be separated from the latter which has few or no bracts among the flowers that are white margined, and are usually less than 7 cm high.

Closeflowered Knotweed: Polygonum polygaloides ssp. confertiflorum (Synonyms: Polygonum confertiflorum, Polygonum imbricatum, Polygonum kelloggii var. confertiflorum, Polygonum watsonii) -

Closeflowered knotweed from Hunters Prairie, near Bear Springs, Mt. Hood N.F........May 28, 1994.

Habitat:

Closeflowered knotweed may be found in grassy areas or vernal pools or on dry open ground.

Range:

Closeflowered knotweed may be found east of the Cascade Mts. from Kittitas County, Washington south to California and east to Idaho and central Montana.

It may be found in the Columbia River Gorge between the elevations of 600'-2700' from Bingen, WA to near Horsethief Butte.

Paul Slichter