Dalea purpurea Vent.

Purple Prairie Clover

© DETenaglia

Family - Fabaceae/Faboideae

Habit - Perennial forb with a thick, dark brown to black, woody rootstock, sometimes with a thick, knotty caudex.

Stems - Erect, sometimes slightly arched, to 80 cm, relatively few-branched toward the tip, occasionally unbranched, finely angled above the midpoint, the angles usually stronger and riblike below the nodes, glabrous or pubescent with inconspicuous, fine, curved hairs, rarely densely woolly, mostly lacking gland-dots.

	Stem. Hairiness is variable.
© DETenaglia

Leaves - Alternate, odd-pinnate, stipulate, 1.5-4.0 cm long, sometimes appearing in fascicles, with 2-5 smaller trifoliate leaves at the base of the main leaf. Petioles punctate-glandular, villous, with adaxial groove. Blades with the rachis 10-20 mm long, gland-dotted, those of the main leaves with usually 5 leaflets. Stipules 2-4 mm long. Leaflets 10-24 mm long, 1.0-1.4 mm wide, linear to narrowly oblanceolate, angled to somewhat tapered at the base and tip, folded longitudinally, the upper surface glabrous, the undersurface gland-dotted and sometimes also sparsely and inconspicuously hairy, rarely densely hairy.

	Stem and leaves.
© SRTurner

	Leaf adaxial.
© SRTurner

	Leaf abaxial.
© SRTurner

	Pressed leaves.
© DETenaglia

Inflorescence - Dense, indeterminate, cylindrical spikes 2-5 cm long, the stalk 1-6 cm long, the axis densely pubescent with short, bristly hairs (viewing the axis requires removal of flowers or fruits), with numerous bracts, persistent until the fruits are shed, 2.5-5.0 mm long, 1-2 mm wide, lanceolate-tapered to strongly tapered above an oblanceolate to ovate base, green or more commonly reddish-tinged above a membranous base, the expanded lower portion glabrous to sparsely hairy and sometimes gland-dotted, the tapered terminal portion densely hairy, with a pale thin band along the margin, this also hairy.

	Inflorescence.
© SRTurner

	Inflorescence, top view.
© SRTurner

	Inflorescence, lateral view.
© SRTurner

Flowers - Calyces with the tube 2.0-2.6 mm long, densely hairy, angled but not noticeably ribbed, not gland-dotted but often with minute reddish to brownish purple spots, the lobes 1.0-1.9 mm long, lanceolate to ovate, sometimes with minute reddish-purple spots, densely hairy. Petals pale to deep pinkish purple or reddish purple, the banner with the expanded portion 1.4-2.6 mm long, the wing and keel petals similar, attached along the rim of the stamen tube, the expanded portion 2.5-3.5 mm long. Stamens 5, the filament tube 2-3 mm long, the free filaments 2-3 mm long, the anthers orangish yellow.

	Young flowers with stamens not yet expanded.
© DETenaglia

Fruits - Short legumes, mostly included in the persistent calyx, 2.1-2.6 mm long, firm and densely hairy above the membranous basal portion, gland-dotted.

Flowering - May - July.

Habitat - Upland prairies, glades, tops of bluffs, forest openings, savannas, pastures, cemeteries, railroads, roadsides.

Origin - Native to the U.S.

Lookalikes - None.

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 the papilionaceous floral structure. It is found across most of Missouri, but is uncommon or absent in the northwestern and southeastern corners of the state. Beyond Missouri it occurs within a broad swath in the central U.S., and also ranges northward into Canada. It is easily recognized when flowering by its distinctive inflorescences, which are a bit reminiscent of purple tutu skirts.

This plant is common yet striking to look at. The foliage and stems can be glabrous or densely pubescent, and some authors have subdivided the species based on this and other characteristics. It is most often found in habitats which are not extensively disturbed. The plants are frequented by flying insects such as butterflies.

Missouri's plants are assignable to var. purpurea. A synonym for the plant is Petalostemon purpureum (Vent.) Rydb.

Photographs taken at Alley Spring, MO., 6-13-03 (DETenaglia); also at Onondaga Cave State Park, Crawford County, MO, 6-19-2014; and near Tecumseh, Ozark County, MO, 7-2-2020 (SRTurner).