Carex and other sedges (Cyperaceae) of San Mateo County and Santa Cruz Mountains Bioregion's Journal

B. maritimus subsp. paludosus vs. B. robustus

• Styles all or mostly 2-fid, vs. Styles 3-fid or a few 2-fid
• Achenes usually biconvex, rarely compressed trigonous vs. Achenes mostly trigonous, or biconvex or compressed-trigonous with low, rounded abaxial angle
• Leaf sheath fronts usually membranous at mouth, veins diverging proximal to summit leaving triangular, veinless area vs. Leaf sheath fronts usually papery at mouth, veins reaching nearly to summit
• Floral scales hyaline vs. Floral scales nearly opaque, papery
• Floral scale awns 0.25 mm at base vs. Floral scale awns 0.5 mm at base [~0.3-0.5]
• Anthers yellow vs. Anthers brownish orange

words and shapes

• Trigonous = 3-angled
• Biconvex = Lenticular = Lens-shaped
• Obscurely trigonous = compressed trigonous = Plano-convex [flat on one side and convex on the other]

B. robustus -- Peri biconvex to obscurely trigonous; Floral scale awns 0.5 mm at base

FNA genus Bolboschoenus

1. Inflorescences with all spikelets sessile or not more than 1/2 on evident branches; perianth bristles not persistent on shed achene or 1–few bristles weakly persistent; achenes biconvex or compressed-trigonous with low, rounded abaxial angle; achene epidermal cells appearing greatly enlarged in cross section, 2–3+ times deeper than wide; styles 2–3-fid; habitats brackish to saline. . . . > 2
2. Inflorescences with all or most spikelets on evident, elongated branches; perianth bristles tightly attached to shed achene, rarely some or all falling separately; achenes equilaterally trigonous to compressed-trigonous or rarely some biconvex; achene epidermal cells appearing small in cross section, isodiametric or very rarely enlarged and to 3 times deeper than wide (in B. novae-angliae); styles mostly 3-fid; habitats fresh to slightly brackish. . . . > 3
3. Floral scales hyaline, membranous, awns 0.25 mm wide at base; anthers yellow, rarely orange; styles 2-fid, rarely 3-fid; achenes usually biconvex, rarely compressed trigonous; leaf sheath fronts usually membranous at mouth, veins diverging proximal to summit leaving triangular, veinless area. . . . Bolboschoenus maritimus
4. Floral scales nearly opaque, usually papery, awns 0.5 mm wide at base; anthers brownish orange; styles 3-fid or a few 2-fid; achenes mostly trigonous; leaf sheath fronts usually papery at mouth, veins reaching nearly to summit. . . . Bolboschoenus robustus

Evergreen

• C. barbarae
• C. obnupta
• C. pendula

Hairy perigynia

• C. brevicaulis (C. zikae)
• C. globosa
• C. gynodynama
• C. pellita
• C. spissa

Hairy foliage (sheaths, at least at mouth, or blades)

• C. amplifolia
• C. gynodynama
• C. pellita

Leaves sometimes > 1 cm wide

• C. amplifolia
• C. hendersonii
• C. pendula
• C. spissa

Serpentine seeps

• C. hassei
• C. serratodens
• C. schottii

Dense tussocks among rocks in streambeds

• C. nudata

Fruit usually aborted

• C. barbarae

Naturalized, garden escape

• C. divulsa subsp. divulsa
• C. pendula

As mentioned in the Project summary, Carex is the largest genus in California where around 200 species occur, and one of the largest genera in the world with over 2,000 species. Due to the minor morphological differences between the species, it is often difficult to identify to species by sight. Source: CA Biologist's Handbook.

The inconclusiveness of identification by visual gestalt without examining inflorescence, spike, flower, and vegetative characters, which often involves dissection and micro-measurements, is especially significant and pertinent to observations of locally uncommon and/or look-alike sedges, typically members of the same subgroup with similar visual gestalts: for example C. bolanderi and C. leptpoda; C. subbracteata, C. harfordii, and C. pachystachys; C. nudata and S. senta, etc.).

C. subbracteata and C. pachystachys and other Broomsedges* illustrate these issues:

Occasionally, iNat guide photos are atypical and consequently misleading -- [https://www.inaturalist.org/photos/33610594] -- for visual gestalt, as in the case of the common central coast and California Floristic Province endemic Carex harfordii; compare with records in this project. Accurate visual search image(s) is important, and needs to be combined with close examination of both inflorescence and vegetative characters.

Indeed many iNat Carex records, including some of our own, tell one not much beyond this is a sedge growing in some or another area. Reports usually lack comments or photos documenting diagnostic characters, size of population, ecology. Taking a photo and relying on Computer Vision for identification does not work for most graminoids. When one suggests an identification, iNat prompts "Tell us why . . ." ; few answer. This prompt should also appear when making the original posting: Computer Vision, Uncertain, Recognized from previous determination, Keyed in a relevant flora, etc.

A guide with macro-photos is Field Guide to the Sedges of the Pacific Northwest and California, 2nd ed., by Barbara L. Wilson, Richard E. Brainerd, Danna Lytjen, Bruce Newhouse, and Nick Otting of the Carex Working Group.
Peter F. Zika, Andrew L. Hipp & Joy Mastrogiuseppe 2015, Carex, in Jepson Flora Project (eds.) Jepson eFlora, Revision 3, accessed on November 25, 2023.
Peter W. Ball & A. A. Reznicek, Carex, in Flora of North America, www.eFloras.org, accessed on November 25, 2023.

Notes
*Broomsedges, Section Ovales; 2 styles, spikes gynecandrous (pistillate above), perigynium winged, stems hollow.