| Author | T.S. Patrick | |
| Distribution | Occurs throughout the northern Mountains and adjacent northwestern Piedmont foothills. It ranges south to Burke County.
A species generally of the Ridge and Valley and Cumberland Mountans/Plateau, and ranging eastward into the New River drainage, and barely south into adjacent areas. However, it is absent from the southern Blue Ridge Mountains region, at least in the middle and higher elevations. The range extends from WV and western VA south to northwestern NC, northwestern GA, and northeastern AL. In TN it is absent from the Blue Ridge but occurs in a northeast-southwest zone through the east-central part of the state. | |
| Abundance | Fairly common to locally common within its fairly small range, at least in the New River drainage portion in Ashe, Alleghany, and northern Watauga counties. Rare to uncommon farther southward. It is not state listed nor is on the NC NHP Watch List. | |
| Habitat | This is a trillium of rich to fairly rich forested soils, though it is not as strictly tied to circumneutral soils as some others. It favors Northern Hardwood Forests and Rich Cove Forests, and is one of the more frequently seen trilliums (along with T. grandiflorum) on forested slopes in the Amphibolite Mountains of Ashe and northern Watauga counties.
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| Phenology | Blooms in April and May, and likely fruits in June and July. | |
| Identification | This is a usually maroon-red flowering trillium similar to T. erectum, from which it was split out a few decades ago. Basically, it is quite similar to T. simile of the central and southern mountains of the state, though that species is white-flowered as opposed to normally red-maroon. T. sulcatum grows to about 1.5 feet tall and has large rhombic leaves averaging about 5 inches long and across. Like those two species, it has an erect flower stalk about 4 inches high, and the single flower is typically facing horizontally. The widely ovate petals are 1-1.5 inches long and nearly as wide, and thus they overlap at their bases. Like T. simile, the petals are angled forward and not flat (in a single plane as in T. erectum); as a result, the flower is cup-shaped and not in a single plane. In addition, the plant is named after the sepals, which are sulcate (grooved at the tips), though that character is likely not needed for identification. However, any white-flowered individuals could be confused with T. simile, but T. sulcatum has smaller flowers, the petals only slightly longer than the sepals, and the sepals contain some purple color. A hike on some of the mountains in Ashe and northern Watauga counties should produce this species. | |
| Taxonomic Comments | Until the latter part of the 20th Century, it was subsumed within T. erectum, but was never a named variety or subspecies.
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| Other Common Name(s) | Southern Red Trillium, Furrowed Wake-robin, Sulcate Toadshade | |
| State Rank | S3 | |
| Global Rank | G4 | |
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| US Status | | |
| USACE-agcp | | |
| USACE-emp | | |
