Vascular Plants of North Carolina
Account for Swamp Buttercup - Ranunculus septentrionalis   Poiret
Members of Ranunculus with account distribution info or public map:
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Section 6 » Family Ranunculaceae
AuthorPoiret
DistributionPresent over most of the central and eastern Piedmont, and in much of the Coastal Plain, but seemingly absent in the far eastern portions and in the Sandhills region. Present in the southern mountains, but apparently absent in the northern mountains and perhaps the adjacent Piedmont.

This species ranges across the Eastern states, though not widespread; it ranges from NY and MN south to northern FL and eastern TX.
AbundanceInfrequent (though can be locally numerous in a few places) in the northeastern Piedmont and northern Coastal Plain, south to Lee, Harnett, Johnston, and Washington counties. Quite uncommon west to the central Piedmont (to Stokes, Davidson, and Union counties), as well as in the Coastal Plain south to Pender and New Hanover counties. Very rare in the southern mountains. Seemingly absent in other places. The NCNHP's State Rank of S2S3 is certainly too conservative, considering that the range map shows records for at least 32 counties (nearly 1/3rd of the state's counties). The editors suggest S3S4 is more appropriate, as it is by no means a rare plant in the state.
HabitatThis is a wetland species of buttercup, usually found in wet bottomland forests or drier spots within swamp forests. It can occur in marsh edges but is not truly a marsh species.
PhenologyBlooms from March into August, though usually in spring; fruits shortly after flowering.
IdentificationThis is a rather smooth and somewhat sprawling or leaning buttercup of damp forests. The flowering stem can reach to 2 feet long, but the basal leaves are not at high. The several basal leaves are on long and mostly smooth petioles, deeply cleft into 3 segments, with the middle segment usually 3-parted/forked. Thus, the leaves tend to be more heavily divided than in the similar R. hispidus, which also has strongly hairy petioles. There are similar but smaller stem leaves, and at the ends of the several flowering stalks are the solitary flowers. Each flower has 5 bright yellow petals, obovate in shape, and the spread flower is slightly below 1 inch across. The green sepals are clearly reflexed (swept back), whereas those of R. hispidus are spreading, just below the petals. Swamp Buttercup is somewhat colonial or at least sprawling, whereas R. hispidus tends to be distinctly solitary plants. Although there are a few other buttercups that grow in wet woods, especially one or two small-flowered species, this is the most likely large-flowered buttercup you will find when working in bottomlands and drier swamps, in the spring or early summer. Make sure the plant is reasonably smooth on the petioles, somewhat more highly dissected in the leaves, and in flower shows swept-back sepals, before claiming this infrequent species (as the widespread and common R. hispidus can also be found in such wetland forests).
Taxonomic CommentsThis species has gone through a number of taxonomic changes, and some references today -- such as NatureServe -- still do not consider it as a valid species, but list it as R. hispidus var. nitidus. RAB (1968) and some others considered it as R. carolinianus. Because NatureServe does not consider this as a valid species, this website, which follows Weakley (2018), must change the NatureServe Global Rank; as it has var. nitidus as T5, then the rank for R. septentrionalis becomes G5Q on this website.

Other Common Name(s)Carolina Buttercup
State RankS2S3 [S3S4]
Global RankG5T5 [G5]
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