Crotalaria sagittalis (Rattlebox)
|Also known as:||Arrowhead Rattle-box|
|Habitat:||sun; dry, sandy or gravelly soil; prairies, along railroads,|
|Bloom season:||June - September|
|Plant height:||4 to 16 inches|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Racemes of 1 to 4 pea-shaped flowers on branching stems in the upper plant, alternating with and opposite to the leaves. Flowers are about 1/3 inch long, yellow, with a broad, nearly round erect petal at the top (the standard) that is barely notched at the tip, and 2 shorter lateral petals extending out over the green keel. The calyx holding the flower is short-stalked, 5-pronged, the prongs as long as or longer than the petals, and covered in long white hairs. Only a few flowers may be open at a time.
Leaves and stems:
Leaves are 1 to 3 inches long, to 2/3 inch wide, lance to elliptic, toothless, covered in long white hairs on both surfaces, rounded to pointed at the tip, stalkless or short-stalked. Stems are erect and branching, densely hairy, green to purplish. Where the raceme stalk meets the stem is a joined pair of leafy appendages (stipule) about ½ inch long, extending down the stem and each side 1-pronged at the tip.
Rattlebox is not commonly encountered, only present in a few Minnesota counties as we are on the northern fringe of its natural range. It is listed as a Special Concern species in Wisconsin and was designated as such in Minnesota in 2013 due to its low populations and the dwindling prairie and savanna habitats this species calls home.
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Photos by K. Chayka taken at Whitewater WMA, Winona County. Photos courtesy Peter M. Dziuk taken in Winona County and in a private garden in Anoka County.
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