Peritoma serrulata (Rocky Mountain Beeplant)

Plant Info
Also known as: Spider-flower, Pink Cleome, Stinking Clover, Stinkweed
Genus:Peritoma
Family:Cleomaceae (Spider Flower)
Life cycle:annual
Origin:Western US
Habitat:part shade, sun; sandy or gravelly soil; prairies, roadsides, railroads, open woods, dunes
Bloom season:July - September
Plant height:1 to 5 feet
Wetland Indicator Status:GP: FACU MW: FACU NCNE: FACU
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: 4-petals Cluster type: raceme Cluster type: round

[photo of flowers] Elongating cluster of showy stalked flowers at the ends of branching stems, with many flowers blooming in a rounded cluster at the tip and fruit forming below. Flowers are ½ to 2/3 inch across with 4 petals that are oblong to narrowly egg-shaped, abruptly narrowed near the base, and asymmetrically arranged. Color ranges from nearly white to pink to purplish. Protruding from the center are 6 long, straight, purple-tipped stamens up to 1 inch long.

[photo of sepals] The 4 sepals are about 1/8 inch long, green to purple and fused for about half their length, forming a bowl with 4 triangular lobes. Flower stalks are slender and often purple. At the base of the stalk is a leaf-like bract nearly as long as the attendant stalk. All parts are hairless.

Leaves and stems: Leaf attachment: alternate Leaf type: compound Leaf type: palmate

[photo of leaves] Leaves are mostly compound in 3's, becoming single near the flower clusters, and have a somewhat repugnant odor. Leaflets are 1 to 2½ inches long and about ½ inch wide, narrowly lance-elliptic and pointed at the tip. The lower compound leaves are long-stalked, becoming shorter stalked as they ascend the stem with the uppermost leaves short-stalked to stalkless. Edges are toothless and may have sparse, long hairs when young but become hairless with age. Stems are hairless, green, and few to many branched with the branches mostly ascending.

Fruit: Fruit type: capsule/pod

[photo of fruit ©Matt Lavin] Fruit is a slender, dangling, 2-chambered pod, 1 to 2 inches long and containing 12 or more seeds, the pod slightly constricted between seeds.

[close-up of seed] Seeds are kidney to egg-shaped, about 1/8 inch (to 4mm) long, mottled brown with an intricate network pattern across all surfaces that reminds me of stained glass.

Notes:

Rocky Mountain Beeplant, formerly Cleome serrulata, is a western species of prairies and grasslands, though sometimes considered a roadside weed. All but one of the six records from Minnesota were collected in the 1880s and 1890s and were likely waifs or introductions that did not persist. The national map indicates it is rare in Minnesota, but the DNR considers it non-native in the state and we agree. It is available in the nursery trade and, as the common name suggest, popular with native bees. It is vaguely similar to the related Red-whisker Clammyweed (Polanisia dodecandra), which has much smaller white flowers, erect pods, is covered all over in sticky hairs, and typically of smaller stature. Both have a disagreeable odor, especially when crushed.

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More photos

Photos courtesy Peter M. Dziuk taken in his garden in Ramsey County. Peritoma serrulata fruit and habitat By Matt Lavin from Bozeman, Montana, via Wikimedia Commons, used under CC BY-SA 2.0

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