Robinia hispida (Bristly Locust)

Plant Info
Also known as: Prickly Locust, Rose Acacia
Genus:Robinia
Family:Fabaceae (Pea)
Origin:southeast US
Habitat:part shade, sun; disturbed soil; roadsides, woodlands, woodland edges, fence rows, waste areas
Bloom season:June - July
Plant height:3 to 10 feet
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

Pick an image for a larger view. See the glossary for icon descriptions.

Detailed Information

Flower: Flower shape: irregular Cluster type: raceme

[photo of flowers] Showy, hanging racemes in leaf axils and tips of 1-year-old branches, each cluster with up to 15 pale to bright rose pink pea-like flowers. The flowers are about 1 inch long, the broad upper petal (standard) erect with a spot of greenish yellow at the base, the lower petal (keel) hiding the 10 stamens and single slender, curved style. The calyx surrounding the base of the flower is tubular, about ¼ inch long, purplish to green with 5 triangular lobes that are long-tapering to a pointed tip. The calyx and flower stalks are all moderately to densely covered in a mix of short white hairs and longer, spreading, red bristles. Bristles have a small, sticky gland at the tip.

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

[scan of compound leaf] Leaves are alternate, once compound, 6 to 12 inches long with 7 to 13 leaflets, the lowest pair usually smallest. Leaflets are elliptic to egg-shaped to nearly round, 1 to 2½ inches long, mostly rounded at the base, rounded and tip with a minute sharp point at the apex. Edges are toothless, the upper surface smooth, lower surface with sparse white hairs on the surface and major veins and scattered red prickles along the midrib.

[photo of new twig and leaf stalks] Young shoots and leaf stalks are green and covered in a mix of short white hairs and longer, spreading, glandular red bristles. A the base of leaf and leaflet stalks are narrow appendages (stipules), those on the leaflet stalks smaller that those of the compound leaf.

[photo of older branch prickles] Branches become darker gray-brown with pale lenticels (pores) the second year, the red bristles turning brown and stiff, eventually dropping off except for a pair of larger, stiff prickles at each node though they, too, eventually drop off. Older bark is gray-brown with scattered shallow furrows. Stems are single or multiple from the base and can form dense thickets from root suckers.

Fruit: Fruit type: capsule/pod

[photo of developing fruit ©Daniel L. Nickrent] Fruit is a flat pod 2 to 3 inches long, green turning brown at maturity, and densely covered in red prickles. Pods contain 3 to 5 seeds.

Notes:

Native to the southeastern US, Bristly Locust's showy flowers and bristly stems and fruits likely made it an attractive addition to the garden trade. Unfortunately it escapes cultivation, can produce dense colonies through root suckering and can be difficult to manage without resorting to toxic chemicals. There are few records of it in the Bell Herbarium but we are seeing it more and more in the wild; additional Minnesota populations are currently being tracked at EDDMapS. It is readily identified at virtually any stage of growth from the compound leaves with red-prickly stalks and young branches, the prickles persisting through the second year, though turning brown. There are several varieties of Robinia hispida, all of which are native to various parts of the southeastern US.  The vars are poorly documented but only var. hispida has been officially recorded in Minnesota.

Please visit our sponsors

  • Minnesota Native Plant Society

Where to buy native seed and plants ↓

Map of native plant purveyors in the upper midwest

  • Shop for native seeds and plants at PrairieMoon.com!
  • Shooting Star Native Seeds - Native Prairie Grass and Wildflower Seeds
  • Morning Sky Greenery - Native Prairie Plants
  • Minnesota Native Landscapes - Your Ecological Problem Solvers
  • Natural Shore Technologies - Using science to improve land and water

More photos

Photos by K. Chayka taken in Aitkin, Pine and Ramsey counties. Photos by Peter M. Dziuk taken in Aitkin, Pine, Ramsey and Renville counties. Photos by Daniel L. Nickrent used by permission via PhytoImages.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Steve Poole - Myre Big Island State Park
on: 2019-06-07 16:14:17

I do not see this on the EEDM map. Should I follow up?

Posted by: K. Chayka
on: 2019-06-20 18:48:42

Steve, I'd add it to EDDMapS. Maybe someone in the park system will follow up.

Posted by: Pat W - Pillager, mn
on: 2019-07-30 21:52:25

Found it starting to grow in my yard this summer. It evidently jumped into my neighbors woods and then into mine. It seems to be very invasive. I'm glad I caught it n time.

Posted by: Laura Miller - Burnsville
on: 2020-06-10 06:12:07

I found this plant blooming in a very large group at Ritter Farm Park, lakeville mn. 6/9/20

Posted by: S Henriksen - Brainerd
on: 2020-06-13 18:11:21

Found in my moms yard and here and there thru their neighborhood - east side of Gull Lake. is there a recommended way to eradicate it? Does it need to be reported at all? Very invasive!!

Posted by: K. Chayka
on: 2020-06-13 18:30:15

S Henriksen, pull or dig it out, but if it is abundant you may have to resort to chemical warfare. This species isn't on any official weed list (only the worst of the worst may be listed) so there isn't anyone tracking it. Sad, because it is getting worse.

Posted by: Pam Potter - Ney Park, Maple Lake
on: 2020-06-26 19:01:54

I've found several of these growing along the roadside in Ney Park by my home.

Posted by: Mike Friendshuh - Becker
on: 2020-07-05 10:52:42

Growing at my parents place, 8 miles north of Becker. Been there for years, my mother passed away 10+ years ago and the yard has been somewhat neglected, and the weed has spread profusely. My brother cut, dug and tilled as much as he could this spring, and is pulling new shoots as they sprout, but having trouble keeping up.

Posted by: Marilyn - Hackensack, Cass County
on: 2020-07-26 09:09:42

Several neighbors have this in their yard.

Post a comment

Note: All comments are moderated before posting to keep the riff-raff out. An email address is required, but will not be posted—it will only be used for information exchange between the 2 of us (if needed) and will never be given to a 3rd party without your express permission.

For info on subjects other than plant identification (gardening, invasive species control, edible plants, etc.), please check the links and invasive species pages for additional resources.



(required)




Note: Comments or information about plants outside of Minnesota and neighboring states may not be posted because Id like to keep the focus of this web site centered on Minnesota. Thanks for your understanding.