Bolboschoenus fluviatilis
Bolboschoenus maritimus
bolboschoenus fluviatile, river bulrush, river tuber-bulrush, scirpe fluviatile
alkali bulrush, bayonet-grass, cosmopolitan bulrush, salt-marsh bulrush, saltmarsh tuber-bulrush, scirpe maritime, seacoast bulrush, seacoast tuberous bulrush
100–200 cm × 5–15 mm.
50–150 cm × (1–)3–8 mm.
sheaths reaching to middle of culm or higher, fronts convex (to concave) and papery at mouth, veins reaching apex, very rarely diverging leaving triangular, veinless, membranous area;
widest blade 7–22 mm wide.
sheaths reaching ± to mid culm, fronts usually membranous at mouth, apex concave to convex, veins diverging proximal to summit leaving triangular, veinless area (often disintegrating);
widest blade 2–12 mm wide.
subumbellate, with all or most spikelets solitary or in clusters of 2–3(–8) on 4–12 rays, rays not exceeding 10 cm;
involucral bracts that surpass inflorescences 3–6, widest bract 4–15 mm wide.
with all spikelets sessile, simply branched with not more than 1/2 of spikelets solitary or in clusters of 2–10 on 1–4 rays, rays not exceeding 8 cm;
involucral bracts that surpass inflorescences 1–4, widest bract 1–6 mm wide.
10–40, ovoid to lanceoloid, 10–25 × 6–10 mm, base cuneate to rounded;
scales often loosely imbricate, orange-brown to stramineous, usually obscurely lineolate-spotted, 7–10 × 3–4 mm, membranous and translucent, apex 2-fid 0.5–1 mm deep, awns fairly stout, 2–3 × 0.5 mm wide at base.
(1–)2–40, ovoid to lanceoloid, 7–40 × (4–)7–10 mm, base usually cuneate to rounded;
scales often loosely imbricate, bright orange-brown to stramineous, often obscurely lineolate-spotted, 5–8 × 3–4 mm, membranous, translucent, apex acute, 2-fid 0.5–1 mm deep, awn slender, 1–3 × 0.25 mm at base.
perianth bristles tightly attached to shed achene, pale brown, very stout, equaling achene;
anthers yellow, 4 mm;
styles 3-fid.
perianth bristles not persistent on shed achenes or sometimes 1–few weakly persistent, medium brown, to 1/2 achene length;
anthers yellow, very rarely orange, 2–4 mm;
styles 2–3-fid.
grayish or dark brown, often in patches, obovoid to obpyriform, all nearly equilaterally markedly trigonous to slightly compressed, angles equally rounded, 3.8–5.5 × 2–2.9 mm, apex rounded, beak 0.2–0.8 mm, surface rather dull, exocarp cells usually not evident at 20X; in cross section exocarp much thinner than mesocarp and its cells very small, isodiametric;
achene specific gravity greater than water.
medium to dark brown, rarely yellowish or whitish, obovoid, biconvex, or concave-sided, rarely obtusely compressed trigonous, 2.3–4.1 × 1.9–2.8 mm, apex rounded to nearly truncate, beak 0.1–0.4 mm, surface glossy, exocarp (epidermal) cells usually clearly visible at 10–20X; in achene cross section exocarp 2 times as thick as mesocarp, its cells greatly enlarged, at least 3 times deeper than wide;
achene specific gravity much less than water.
= 94.
Bolboschoenus fluviatilis
Bolboschoenus maritimus
Bolboschoenus fluviatilis frequently forms dense, monospecific, often entirely vegetative stands, and it is more common than recorded because vegetative colonies are often overlooked (E. W. Chester and B. E. Wofford 1992). The only record for Alabama is an 1870 collection from the East Fowl River in the Mobile Delta, where the species has not been collected since. It was intentionally introduced into New Hampshire (D. J. Padgett and G. E. Crow 1993). The report from New Mexico by M. L. Fernald (1950) cannot be confirmed because no specimen is known.
Putative hybrids with Bolboschoenus maritimus occur in California. Bolboschoenus novae-angliae probably originated from B. fluviatilis × B. robustus (J. Browning et al. 1995). Introgression from B. maritimus and/or B. robustus is suggested by the larger exocarp cells (evident in surface view) in some North American plants. The Eurasian B. yagara (Ohwi) Y. C. Yang & M. Zhan differs from B. fluviatilis in its narrower leaves and smaller achenes.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Subspecies at least 2 (2 in the flora).
Bolboschoenus maritimus belongs to a difficult, worldwide complex, in which the delimitation of specific and infraspecific taxa is still unclear. The new lectotype and epitype from the Baltic coast of Sweden selected by S. G. Smith and I. Kukkonen (1999) are used here as the basis for redefining B. maritimus subsp. maritimus, which was previously defined to include B. yagara (Ohwi) Y. C. Yang & M. Zhan (J. Browning et al. 1996; Z. Hroudová et al. 1998).
It seems likely that some populations of both Bolboschoenus maritimus subsp. maritimus and B. maritimus subsp. paludosus have been introduced into the flora from Eurasia.
Putative Bolboschoenus maritimus × B. robustus hybrids are common in zones of sympatry along the northern Atlantic Coast and in California, putative B. fluviatilis × B. maritimus hybrids occur in California, and many B. glaucus × B. maritimus hybrids occur in California and Idaho (J. Browning et al. 1995). They are intermediate between their putative parents in every character studied and are often fertile. Interspecific hybridization is probably responsible for much of the infraspecific variation in B. maritimus, especially along the northern Atlantic and California coasts. The orange anthers and few 3-fid styles on some specimens from southeastern Texas may be due to introgression from B. robustus. The type of Scirpus maritimus forma agonus Fernald is probably a B. maritimus × B. robustus hybrid.
Bolboschoenus maritimus and B. robustus have been widely confused in the southwest, where some authors (e.g., H. L. Mason 1957; P. A. Munz 1959, 1968) have treated B. maritimus as a synonym of B. robustus, and others (D. S. Correll and H. B. Correll 1972) have treated B. robustus as B. maritimus var. macrostachyus Michaux.
No acceptably vouchered chromosome counts for Bolboschoenus maritimus are available from North America. The voucher for the 2n = 90 count by N. A. Harriman (1981) from southeastern Texas is a mixed collection of B. maritimus subsp. paludosus and B. robustus. Reasonably reliable chromosome numbers reported for B. maritimus in Europe are mostly 2n = 108 or 110, but vary from 2n = 55 to 112 (V. Jarolímová and Z. Hroudová 1998).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Styles all or mostly 3-fid; achenes obtusely compressed trigonous or some biconvex in same spikelet; scales dark to medium brown; achenes dark to medium brown. | subsp. maritimus |
1. Styles all or mostly 2-fid; achenes mostly biconvex; scales dark to medium brown to stramineous or nearly colorless; achenes mostly medium brown, sometimes darker or paler. | subsp. paludosus |
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
Go Botany, 
IL Wildflowers, 
KS Wildflowers, 
MD Biodiversity, 
MI Flora, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
- Local floras: BC, OR, WA
- Local Web sites: CalFlora, CalPhotos, Flora NW, Go Botany, IL Wildflowers, KS Wildflowers, MI Flora, MN Wildflowers, MO Plants, PNW Herbaria
- WildflowerSearch
- iNaturalist (observations)
- USDA Plants Database
- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
