Vascular Plants of North Carolina
Account for Rock Buttercup - Ranunculus micranthus   Nuttall
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Section 6 » Order Ranunculales » Family Ranunculaceae
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AuthorNuttall
DistributionPresent only in the northeastern part of the Piedmont, which represents the southeastern corner of the overall range. Known from six counties, though several county records (such as Harnett) have not been verified.

This is a somewhat Midwestern species, ranging mainly north and east of NC. It occurs from MA and eastern KS south to northern NC, AL, and OK.
AbundanceVery rare and declining, with the only records since 2000 appearing to be from Caswell County (at several occasions) and one site in Durham County. This is a Significantly Rare species, as designated by the NCNHP.
HabitatThis species requires high pH (circumneutral) soils, preferably where rich and rocky. Thus, it is mainly limited to the Basic Mesic Forest natural community, especially growing on or very near dark-colored rocks such as amphibolite or gabbro.
See also Habitat Account for Rich Wet-Mesic Hardwood Forests
PhenologyBlooms mainly in March and April, rarely into May; fruits shortly after flowering.
IdentificationThis is a moderate-sized buttercup of a very restricted habitat. It generally resembles in appearance but is conspicuously hairy. It has a few basal leaves with moderate petioles about 1-2 inches long, and a blade that is ovate with small crenations or serrations, about 1 inch long and slightly less wide. The blades are often truncate at the base to slightly rounded; R. abortivus has more cordate bases and leaves not hairy. The one or two flowering stems can reach 8-10 inches high, with a few short branches near the top, and a few insignificant stem leaves. The flowers are very small, with the 5 yellow petals being barely 1/8-inch long. This species should be identified by 1) its occurrence on high pH and very rich soils, often where rocky; 2) the very hairy petioles, leaves, and flowering stems; and 3) the truncate leaf bases. Why it has disappeared from most sites is not clear, as this rich slope habitat is reasonably protected from most impacts other than logging, though the removal or blowdown of even scattered trees could change the microhabitat and introduce exotic species. Also, at the southern edge of a range, possibly global warming or simply stochastic events can cause a species to "blink out", as populations are usually "few and far between" and are normally very small.
Taxonomic CommentsNone

Other Common Name(s)Small-flowered Buttercup
State RankS1
Global RankG5
State StatusSR-P
US Status
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