Petalostemon purpureus (Vent.) Rydb. - Purple Prairie Clover

Petalostemon purpureus plant

Family - Fabaceae

Stems - To -1m tall, simple or branching above, Multiple from base, erect to ascending, glabrous to densely villous, herbaceous.

Petalostemon purpureus stem

Leaves - Alternate, odd-pinnate, stipulate, to -5cm long. Stipules linear, 5mm long. Leaflets typically 3-5, linear to linear-oblong, involute, opposite, -2cm long, 2mm broad, entire, sparse villous, glandular punctate below, subsessile or on very short petiolule to .7mm long. Petiole punctate glandular, villous, with adaxial groove.

Petalostemon purpureus leaves

Inflorescence - Dense, indeterminate, cylindrical spikes to 7cm tall, 1.2cm in diameter, terminating stems.
Each flower subtended by an apiculate bract to 5mm long, +/-2mm broad. Bracts cupped and pubescent below tip.

Petalostemon purpureus inflorescence

Flowers - Petals purplish-pink, clawed, connected to staminal column (column to 3mm long, white, glabrous), 4-6mm long, 1mm broad. Claws to -4mm long. Stamens 5, monodelphous. Filaments 5-6mm long, purplish. Anthers .9mm long, orange. Style 8-9mm long, white to pinkish, mostly glabrous but bearded below, filiform. Ovary 1.4mm long, pubescent at apex. Calyx tube to 3mm long, white, dense pubescent, 5-lobed. Lobes green acute, 1.2mm long, equal, dense pubescent.

Petalostemon purpureus flowersYoung flowers with stamens not yet expanded.

Flowering - June - September.

Habitat - Prairies, glades, open woods, roadsides, railroads.

Origin - Native to U.S.

Other info. - At first glance the flowers and spikes of this plant appear somewhat uncharacteristic of most plants in the bean family. Closer examination reveals that indeed the plant is properly placed.
This plant is common yet striking to look at. The foliage and stems can be glabrous or very pubescent and some authors split the species up into different varieties based on this and other characteristics.
The plants are frequented by flying insects such as butterflies.
Synonyms for the plant include P. purpureum and Dalea purpurea Vent.

Photographs taken at Alley Spring, MO., 6-13-03.


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