Vascular Plants of North Carolina
Account for Littleleaf Sensitive-briar - Mimosa microphylla   Dryander
Members of Fabaceae:
Only member of Mimosa in NC.
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Section 6 » Order Fabales » Family Fabaceae
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AuthorDryander
DistributionOccurs over the Piedmont except absent in the extreme northeastern corner. Found across the southern half of the Mountains but absent from northern counties. In the Coastal Plain, limited to the southwestern third, including the Sandhills region; ranges north and east to Wilson and Craven counties. In summary, it occurs over roughly the central and southwestern 60% of the state.

This is a Southern species, ranging north sparingly to central VA and most of TN, and south to southern FL and eastern LA.
AbundanceFairly common to common in the western, central, and southeastern Piedmont, but scarce in the Triangle region (Wake, Durham, and Orange counties) and farther to the northeast. Fairly common in the southern half of the Mountains. Also, fairly common to common in the southwestern third of the Coastal Plain.
HabitatThis is a species of dry to somewhat mesic woodland borders, openings in woods, and other dry places. It can occur in open pine/scrub oak sandhills and other dry woods, but it is not strongly attracted to sandy soil.
PhenologyBlooms from June to September, and fruits from August to November.
IdentificationThis is a most unusual plant in NC and cannot really be mis-identified. It is the only native plant (other than Venus Flytrap [Dionaea muscipula]) that truly has "sensitive" leaves that close at the slightest touch. It is a prostrate, semi-woody herb that lies on the ground or on other vegetation, growing to about 4-5 feet long. It is sparsely branched, but the essential feature is the evenly bipinnate leaves, with 6-16 pinnae (divided leaflets), and each leaf is about 3-4 inches long. The pinnae are about 1 inch long and have 20-32 pinnules, each very narrow and short. The effect is that each leaf is somewhat fern-like or feather-like; if you touch any part of a leaf, the leaf closes up within a second. Also quite striking are the colorful rose-pink heads of flowers, each being globe-like and about 0.8-inch across, with dozens of small tubular flowers creating a most striking inflorescence. The flower heads resemble small "flowers" of the introduced Mimosa (Albizia julibrissin). Thankfully, this unusual species is frequently seen in the southern and central parts of the state, and it is hard to walk past one without touching a leaf and watching it close up!
Taxonomic CommentsUntil fairly recently it was named as Schrankia microphylla. Some references, such as NatureServe, now name it as Mimosa quadrivalvis.

Other Common Name(s)Eastern Sensitive-briar
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