Vascular Plants of North Carolina
Account for Bog Yellow-eyed-grass - Xyris difformis   Chapman
Members of Xyris with account distribution info or public map:
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Section 5 » Order Commelinales » Family Xyridaceae
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AuthorChapman
DistributionMostly Coastal Plain and Sandhills; scattered records in the Piedmont and southern low Mountains.

Southern ME to southern Ont., south to north peninsular FL and eastern TX.
AbundanceFrequent in the Coastal Plain and Sandhills, rare elsewhere in the Piedmont and southern mountains. Considering that it has been collected in all but a handful of Coastal Plain counties, the State Rank of S3S4 is quite conservative; S4S5 seems more appropriate.
HabitatPond and impoundment margins, beaver ponds, wet pine savannas and flatwoods, montane seepage bogs. In the Sandhills also on shores of blackwater streams.
PhenologyFlowering and fruiting late July-October.
IdentificationIn Bog Yellow-eyed-grass the scape (stem) broadens and flattens in the upper 1-3 inches (be sure to check several scapes). Our other species may broaden slightly immediately below the head, but not as much as half an inch. Scapes reportedly reach 2 feet tall (Godfrey & Wooten 1979), but NC material is seldom more than about 1 foot. Leaves are broadly linear, up to a foot long, and pinkish at the base. Scapes of Irisleaf Yellow-eyed-grass (X. iridifolia) may be somewhat flattened, but it is a more robust plant, with wider leaves and longer heads (mostly 20-25 mm vs. 8-15 mm in S. difformis). See also the more robust Small's Yellow-eyed-grass (X. smalliana).
Taxonomic CommentsFormerly, X. curtissii was treated as a variety of X. difformis, even though stems are not flattened.

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)Flatstem Yellow-eyed-grass
State RankS3S4 [S4S5]
Global RankG5
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