Crotalaria sagittalis (Rattlebox)

Plant Info
Also known as: Arrowhead Rattle-box
Genus:Crotalaria
Family:Fabaceae (Pea)
Life cycle:annual
Origin:native
Status:
  • State Special Concern
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):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: irregular Cluster type: raceme

[photo of flower] 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: Leaf attachment: alternate Leaf type: simple

[photo of leaves] 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.

Fruit: Fruit type: capsule/pod

[photo of fruit] Fruit is an inflated, oblong pod to 1¼ inch long at maturity, initially light green, ripening to purplish black.

Notes:

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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More photos

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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