[Fleeceflowers and Knotweeds: The Genera Aconogonon, Bistorta, Fagopyrum, Fallopia, Persicaria and Polygonum East of the Cascades of Oregon and Washington]
Closeflowered Knotweed, Close-flowered Knotweed, Fruitleaf Knotweed
Polygonum polygaloides ssp. confertiflorum
Synonyms: Polygonum confertiflorum, Polygonum imbricatum, Polygonum kelloggii var. confertiflorum, Polygonum watsonii
The photo above shows a close-up of the inflorescence of closeflowered knotweed as seen in shallow alkaline basins along the old highway to the southwest of Fishtrap Lake in eastern Washington.........May 30, 2008. Note the numerous bracts with white-winged margins within each inflorescence.
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.
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.
The photo above shows a close-up of the inflorescence of closeflowered knotweed as seen in shallow alkaline basins along the old highway to the southwest of Fishtrap Lake in eastern Washington.........May 30, 2008.
Closeflowered knotweed blooming in dry soils along Forest Service Road #1647 in southeastern Logan Valley, Malheur National Forest........July 3, 2010.
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Close-flowered knotweed blooming (at left) in vernally moist soils along the Colockum Pass Road, Wenatchee Mountains..........July 7, 2012. The photo at right shows close-flowered knotweed as seen at the Bickleton Ridge Unit of the Klickitat Wildlife Area........Jun3 17, 2017.
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Close-flowered knotweed observed with mountain tarweed (Madia glomerata) in a vernal pool along the Fishtrap-Sprague Highway near the junction with Miller Ranch Road East......June 28, 2020.
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Closeflowered knotweed from Hunters Prairie, near Bear Springs,
Mt. Hood N.F.........May 28, 1994.
Paul Slichter