Landscape Plants of the Upper Midwest

Black Locust

{Picture of Black Locust}

Plant Information

  • Plant Type: Tree: Large
  • Scientific Name: Robinia pseudoacacia Play audio of plant name
  • Family: Black Locust
  • Zone: 3
  • Plant Size: 40-50'
  • Bloom Color: White
  • Habit: Upright: suckering
  • Culture:

    Extremely adaptable. Tolerates dry sterile soils. Full sun.

  • Notes:

    Blacklocust is not a tree for the residential landscape due to aggressive suckering and branches which are often thorny. Highly fragrant white flowers are borne in June followed by 4" brown-to-black seed pods in fall. May be usable on extremely difficult sites where its suckering will not become a concern.

    Myopic regulations in Wisconsin have unfortunately resulted in this Midwest-native plant being designated as a Prohibited Invasive weed.  Therefore, only in Wisconsin, it cannot be transported, transferred, or introduced without a permit.  To view the complete regulation see: Wisconsin Invasive species rule – NR 40

  • Pruning:Pruning animation

    Structural pruning targets branch defects with the goal of producing strong-branched, long-lived trees with a low risk of storm damage.  The importance of addressing branch defects when trees are young cannot be over-emphasized. The suppression or removal of small branches is far easier and better for long-term tree health than when branches become large.  Beginning when a tree is planted, it should be evaluated each year and branches with structural defects should be suppressed, or if small, removed.  This will promote a resilient tree structure that is also more ascetically pleasing.    

    These site explain the fundamentals of structural tree pruning:

    Urban Tree Foundation – Structural Pruning

    University of Florida – Structural Pruning

    If a branch needs to be removed for clearance, is damaged, or possesses a critical defect, a 3-point cut is used (see animation). First an undercut is made to prevent bark from tearing down the trunk if it remains attached to the falling limb. The branch is then "stub cut" which removes most of the branch to facilitate a clean final cut. The final cut is made just outside the branch collar, which is the swollen area between the branch and the trunk. Cuts made here will heal most readily and prevent rot from invading the main trunk of the tree, a common occurrence when branches are cut flush with the trunk.

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Landscape Plants of the Upper Midwest

Bill Hoch, Associate Professor
Montana State University

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