Taxon Report

Polygonum polygaloides Meisn. ssp. esotericum (Wheeler) Hickman

Modoc County knotweed

Print Report


©2013 Jake Ruygt

Taxon Summary

Polygonum polygaloides ssp. esotericum, commonly known as Modoc County knotweed, is a annual herb in the Polygonaceae that is found in California and elsewhere. It occurs within Great Basin scrub, Lower montane coniferous forest, Meadows and seeps, and Vernal pools, growing at elevations from 885 to 1690 meters. Polygonum polygaloides ssp. esotericum is ranked 1B.3, Plants Rare, Threatened or Endangered in California and Elsewhere; Not very threatened in California.

  Classification
Scientific Name:
 Polygonum polygaloides Meisn. ssp. esotericum (Wheeler) Hickman
Common Name:
 Modoc County knotweed
Family: Polygonaceae
Element Code: PDPGN0L1Y2
USDA Plants Symbol: POPOE
Synonyms/Other Names:
  • Polygonum esotericum Wheeler

Ecology and Life History
Lifeform: annual herb
Blooming Period: May-Sep May-Sep
Elevation: 885-1690 (2905-5545)
General Habitats: Great Basin scrub, Lower montane coniferous forest, Meadows and seeps, Vernal pools
Microhabitat: Mesic
Microhabitat Details:

Conservation Status
CA Rare Plant Rank: 1B.3
Global Rank: G4G5T3
State Rank:
 S3
State List: None
Fed List: None
Other Status: BLM_S; SB_UCSC
CRPR Changes:
  • changed from 1B.1 to 1B.3 on 2017-12-13

Occurrence Data from the CNDDB
Total Occurrences: 45
Element Occurrence Ranks:
   Excellent (A) 5
   Good (B) 10
   Fair (C) 2
   Poor (D) 0
   None (X) 0
   Unknown (U) 28

Location
California Endemic:  False
California Counties and Islands: Name (Code)
Modoc (MOD), Plumas (PLU), Shasta (SHA), Sierra (SIE)
Quads: Name (Quad Code)
Barrel Springs (4111988), Crooks Meadow (4111978), Ambrose (4112058), Antelope Valley (3912063), Beaver Mtn. (4112086), Boles Meadows East (4112067), Boles Meadows West (4112068), Burney Falls (4112116), Calpine (3912064), Crank Mountain (4112142), Davis Creek (4112063), Jacks Butte (4112057), Knobcone Butte (4112151), Lake Annie (4112081), Larkspur Hills (4112071), Lookout (4112122), McGinty Reservoir (4112075), Mt. Bidwell (4112082), Pease Flat (4112085), Reconnaissance Peak (3912073), Rimrock Lake (4112162), South Mtn. (4112076), Spaulding Butte (4112152), Washington Mtn. (4112048), Whitehorse (4112134), Whittemore Ridge (4112066)

Threat List Data from the CNDDB

Threat List Total: 7
EOs with Threat Listed: Total EOs % of EOs
9 20 %
Grazing 6 13%
Non-native animal impacts 3 6%
Foot traffic/trampling 2 4%
Mining 1 2%
Non-native plant impacts 1 2%
Other 1 2%
Road/trail construction/maint. 1 2%

Notes
Possibly threatened by grazing, trampling, road maintenance, and non-native plants. Intermediates to ssp. confertiflorum are common, especially on Modoc Plateau to OR. Difficult to distinguish pure stands of ssp. esotericum in CA; needs further study. Only occurrences that mostly contain P. p. ssp. esotericum are included. See Rhodora 40(476):310-312 (1938) for original description, and Madroño 31(4):251 (1984) for revised nomenclature.
Threats:
Taxonomy:

Selected References

CRPR List Change on 2017-12-13
Citation California Native Plant Society, Rare Plant Program. 2025. Rare Plant Inventory (online edition, v9.5.1). Website https://www.rareplants.cnps.org [accessed 27 January 2025].