Purple Prairie-Clover

 

This pretty flower is purple prairie-clover (Dalea purpurea) and is one of my rescue plants. I found this purple prairie-clover plant growing along the side of a road (which has experienced major reconstruction in recent years) on the bluffs overlooking Duluth, Minnesota. I had seen it growing there with several other prairie plant species for years and would even make special hiking trips just to look at it and the others in bloom. I’d also go there to collect flower tops and leaves of wild bergamot (Monarda fistulosa) and licorice mint (Agastache foeniculum) for teas. Not knowing any better at the time (it was 1993) I dug up a plant and luckily it survived my clumsy work. I watered it often and kept the plant protected from the sun with a sheet of cardboard. It has been a slow growing plant for me and from the one original I now have three plants.

Taxonomy, Distribution, and Description

Purple prairie-clover (Dalea purpurea) is a legume in the family Fabaceae but is not a clover (Trifolium) which is a genus of plants separate from this one. Purple prairie-clover grows in dry to mesic prairies, both tallgrass and shortgrass, other grassland types, and oak savannas from British Columbia and Manitoba in Canada south to Alabama and Arizona in the United States. Although considered an indicator of stable plant communities that have existed with little soil disturbance (such as erosion, plowing, heavy grazing) purple prairie-clover will colonize disturbed soils like along roadsides.

Purple prairie-clover is a perennial herbaceous plant from a deep woody tap root with several lateral roots that can be from 1 to 2 meters long in mature plants. New growth comes from buds at the crown of the tap root. There may be from 2 to 15 stems. The leaves with from 3 to 7 leaflets are small (1 to 4 cm long), numerous, fine textured, with translucent glandular dots, and scattered hairs along the margins. Purple flowers appear from late June to August on the 20 to 90 cm high stems and are later followed by grayish cones of small one-seeded or two-seeded pods.

In the garden

Purple prairie-clover will grow in any deep soil that is dry or well-drained and in full sun. Plants or seeds may be purchased from many sources that specialize in native plants. Sow the seeds where the plants are to grow or in deep pots to be transplanted later. If direct sowing remove any sod and weeds and plant in the fall at a depth twice the thickness of the seeds. Growth can be slow and weeding will be necessary for a few years.

The combination of purple prairie-clover’s fine-textured leaves and short spires of purple flowers is quite attractive when mixed with short bunching grasses such as little bluestem (Schizachyrium scoparium) and prairie dropseed (Sporobolus heterolepis) and low-growing herbs such as white sage (Artemisia ludoviciana).

References consulted

Cochrane, T. S. and Iltis, H. H. (2000). Technical Bulletin No. 191. Wisconsin Department of Natural Resources and University of Wisconsin-Madison Herbarium.

Gleason, H. and Cronquist, A. (1991). Manual of the Vascular Plants of the Northeastern United States and Adjacent Canada, Second Edition. New York Botanical Garden, New York.

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