Taxon Report

Isoetes minima A. A. Eaton

Columbia quillwort

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Species Description:
Isoetes minima, commonly known as Columbia quillwort, is a perennial cormiferous herb in the Isoetaceae that is found in California and elsewhere. It occurs within Meadows and seeps, growing at elevations from 2190 to 2190 meters. Isoetes minima is ranked 1B.1, Plants Rare, Threatened or Endangered in California and Elsewhere; Seriously threatened in California.

  Classification

Scientific Name:
Isoetes minima A. A. Eaton
Common Name:
Columbia quillwort
Family: Isoetaceae
Element Code: PPISO01081
USDA Plants Symbol: ISMI4
Synonyms/Other Names:

Ecology and Life History

Lifeform: perennial cormiferous herb
Blooming Period: Jun Jun
Elevation: 2190-2190 (7185-7185)
General Habitats: Meadows and seeps
Microhabitat: Vernally Mesic
Microhabitat Details:

Occurrence Data from the CNDDB

Total Occurrences: 1
Element Occurrence Ranks:
   Excellent (A) 0
   Good (B) 0
   Fair (C) 0
   Poor (D) 0
   None (X) 0
   Unknown (U) 1
California Endemic:  False
California Counties and Islands: Name (Code)
Modoc (MOD)
Quads: Name (Quad Code)
Mt. Bidwell (4112082)

Notes

Field work needed (population size and extent, site quality and threats, vegetation and associated species, search for more occurrences).
Threats:
Possibly threatened by grazing and trampling.
Taxonomy:
Previously confused with I. howellii; mature female spores (megaspores) distinctive in being densely tuberculate and with a row of spinules along the equatorial ridge.

Selected References

Proposed Addition to California Rare Plant Rank 1B.1, G1G2 / S1 (2023)
Canadian Field-Naturalist 135: 293–304 (2021)
For first CA record see Madroño 67: 63–64 (2020)
Citation California Native Plant Society, Rare Plant Program. 2025. Rare Plant Inventory (online edition, v9.5.1). Website https://www.rareplants.cnps.org [accessed 20 January 2025].