FIRST IMPRESSIONS: Dalea purpurea is an unbranched multi-stemmed perennial wildflower that grows from a stout taproot. Plants have fine textured deep green bean-like foliage. As mid-summer approaches, stems are crowned by dense cylinder shaped spikes of lovely rosy-purple florets. Plants thrive in well drained sunny sites and harsh prairie type habitats.
HABITAT & HARDINESS: Dalea purpurea occurs in central North America from Ontario to Georgia west to Alberta and Arizona. The species is most common in the Great Plains and is absent from the east and west coasts.
Plants are indigenous to mesic tallgrass prairies, Blackland prairies, gravel, sand and hill prairies, limestone glades, savannas, sand hills and sand dunes around Lake Michigan.
Plants are hardy in USDA Zones 3-8.
PLANT DESCRIPTION: Dalea purpurea originates from a sturdy taproot that can penetrate the soils to a depth of 6’.
Young plants have a single unbranched stem. As plants mature they develop multiple stems and a bushy vase-shaped habit.
The alternate leaves are odd-pinnately compound with 3-7 narrow leaflets. Each leaflet is about 1” long and less than ¼” wide with dark green color and smooth margins.
In summer, plants are topped by showy rosy-violet flower spikes. Each dense cylinder shaped spike is 1-2” long and packed with ¼” florets. The florets have 5 small petals and 5 golden-yellow exserted stamens. Blooming begins at the bottom of the spikes and gradually progresses upward during the 4-6 week bloom period.
After blooming, spikes mature into elongated clusters of small bract covered gray to brown seed pods.
Plants are 3’ tall with 1-2’ spread.
CULTURAL & MAINTENANCE NEEDS: Dalea purpurea grows best in sunny sites with average to dry well drained soil. Plants also adapt to loam, sandy, clay, gravelly or alkaline soils.
Young plants expend energy producing beefy taproots and tend to get off to a slow start. After establishment, the deep roots enhance the plants extreme resistance to heat, drought and controlled burns. Excess shade, competition from neighboring plants and disturbance are the only things that can inhibit the growth of this tough guy.
Plants are pest resistant but are often nibbled by deer and other herbivores.
LANDSCAPE USES: This unique species is a wonderful Accent Plant for a Wildlife Garden or Prairie Restoration. Dalea purpurea can also be used as a Butterfly Nectar Plant or Cut Flower. Plants provide Showy Blooms, Erosion Control and are appropriate for Cottage Gardens, Rock Gardens, Water-wise Landscapes, Low Maintenance Plantings and Perennial Borders.
COMPANION & UNDERSTUDY PLANTS: Dalea purpurea mingles well with prairie residents like Allium cernuum, Asclepias tuberosa, Echinacea purpurea and Liatris aspera. This species also combines beautifully with prairie grasses like Andropogon gerardii. Panicum virgatum, Sorghastrum nutans and Sporobolus heterolepis.
Baptisia australis is a legume relative with purplish flower color and similar cultural needs that might be substituted in a pinch.
TRIVIA: Honeybees, native bees, wasps, butterflies, skippers, moths and beetles seek nectar and pollen from the flowers. Plants host caterpillars of Dogface sulfur butterflies.
Dalea purpurea was formerly known as Dalea violacea, Kuhnistera violacea, Psoralea purpurea Petalostemon violaceum, P. pubescens, P. purpureum and P. standleyanus.
This member of the Legume or Pea Family was used medicinally by Native Americans. It has recently been found to contain opiate alkaloids.