Vascular Plants of North Carolina
Account for Arrowhead Rattlebox - Crotalaria sagittalis   L.
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Section 6 » Order Fabales » Family Fabaceae
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DistributionEssentially throughout the Piedmont, though of spotty occurrence; ranging into the northwestern Coastal Plain, and also a few areas of the mountains. Generally absent in the Coastal Plain and most of the mountains (though its "absence" there is puzzling).

This species has a rather odd range. It ranges north to southern New England west to MN, and south to the FL Panhandle and eastern TX. However, it is scarce to absent in the mountain regions (Appalachians and Cumberlands).
AbundanceGenerally uncommon in the Piedmont, and rare in the northwestern Coastal Plain. Very rare in the mountains (known so far just for Alleghany and Cherokee counties). This is another Crotalaria species that has declined markedly in the state, as have C. purshii and C. rotundifolia (both in the Coastal Plain). For example, Blomquist and Oosting (1959) call it "Frequent" in the state's Piedmont region; however, today it is nowhere near this numerous or often seen. Reasons for the decline are likely due to development, re-vegetation of abandoned fields, fire suppression, and other factors.
HabitatThis is a species of fairly circumneutral (moderately high pH) soils, but in dry and mostly sunny places. It favors wooded borders, old fields, various types of glades and barrens, and other typically disturbed ground.
PhenologyBlooms from June to August, and fruits from July to September.
IdentificationThis is a rather small and rather "typical-looking" herbaceous plant, growing to about 8-10 inches tall. It is quite pubescent overall, with only a few scattered ascending branches. The simple leaves (not divided into leaflets) are narrowly elliptic, about 2 inches long and about 1/2-inch wide, and are sessile. One helpful identification feature is that upper leaves have small stipules, forming downward-pointing green "arrowheads", not nearly as large or conspicuous as those of C. purshii, but on an otherwise bland-looking plant, can be noticeable at close range. At the ends of the scattered branches are few-flowered racemes of small yellow flowers, each being about 1/3-inch long. The pods that follow are about 1 inch long and widely cylindrical, and can be conspicuous in late summer when they dangle downward on the slender stalks. This is a species that most biologists probably are not familiar with, or do not see often, especially as it draws little attention with showy flowers or large leaves. Nonetheless, finding it can often lead the observer to a few other rare or uncommon species in its dry and usually high pH soil conditions.
Taxonomic CommentsNone

Other Common Name(s)Common Rattlebox
State RankS3? [S3S4]
Global RankG5
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