Vascular Plants of North Carolina
Account for Slender Yellow-eyed-grass - Xyris torta   J.M. Smith
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Section 5 » Order Commelinales » Family Xyridaceae
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AuthorJ.M. Smith
DistributionMountains and Piedmont; disjunct to Onslow County (no specific location) and to Dare County (Nags Head Woods). The only NC member of the genus essentially limited to the Piedmont and Mountains; all other Xyris are strictly or nearly limited to the Coastal Plain and Sandhills.

NH to WI, south to central GA, TX, and OK.
AbundanceFairly common but local in the Mountains and western Piedmont; very uncommon in the rest of the Piedmont, mainly in northern counties; extremely rare in the Coastal Plain.
HabitatMontane seepages, bogs, freshwater marshes, streambanks, ditches; rarely at pools and wet places on granitic flatrocks and domes. Discovered in extensive, clayey, seepy streamhead ecotones in the Uwharrie Mountains of Montgomery County in 2021.
PhenologyFlowering and fruiting June-August.
IdentificationSlender Yellow-eyed-grass is a medium-sized species and has an expanded, bulbous base and twisted stem and leaves. Thus it resembles Carolina Yellow-eyed-grass (X. caroliniana) (and a number of specimens have been misidentified), but its head is short and ovate (not long and tapered to both ends as in that species) and leaf bases are pinkish-purplish to yellow-green (vs. lustrous chestnut color in X. caroliniana). See Godfrey & Wooten (1979, p. 491) for additional characters.
Taxonomic CommentsNone

Members of Xyris are easy to identify to genus, but can be a challenge to identify species. Careful observation of a few features with a hand-lens is usually sufficient. Close attention must be paid to the flowering head, which is composed of overlapping brown scales. Immediately behind each scale are two brown "lateral sepals"; the margins of these may be feathery or irregularly lacerate (cut into narrow segments) or finely cut into short, comb-like prickles. Lateral sepals may be hidden or a bit longer than each scale. The flowers themselves are usually of little diagnostic value, other than time of flowering -- morning vs. afternoon. Seed size and ornamentation can also be useful characters, but require a dissecting scope to see well. Note also whether leaves and scapes (stems) are twisted and the color of the basal portion. All species have 2-ranked leaves, but in some species the leaves are arranged in a broad, fan-like shape. Finally, note the leaf and stem surface texture -- whether smooth of with little pale bumps. See Godfrey & Wooten (1979) for detailed descriptions and drawings.
Other Common Name(s)Mountain Yellow-eyed-grass, Twisted Yellow-eyed-grass
State RankS3
Global RankG5
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