Cover it up! Using plants to control buckthorn

photo of research team surveying a small plot on a forest floor

Researchers survey a plot as they study using native plants to suppress buckthorn


Common buckthorn (Rhamnus cathartica) is an invasive shrub that outcompetes native plants and degrades Minnesota forests. Minnesotans spend millions each year removing buckthorn from their properties, yet they find the invasive shrub returning to the same spots again and again. Removal of buckthorn is a common forest management activity, but may only provide short-lived benefits since buckthorn has been known to rapidly regrow.

In grasslands, heavily seeding native species can restore native communities and inhibit invasion, but this approach is rarely used in forest management (Schuster et al. 2018). 

This research team investigates whether they could similarly establish enough native plants in forest settings to prevent buckthorn from re-establishing.

Project phases

Phase 1 (complete)

Project information

Research project title: Cover it Up! Using plant to control buckthorn
Taxa: Plant
Species: Common buckthorn (Rhamnus cathartica)
Project status: Completed in 2019
Funding: $327,000

Research questions

  • What native planting techniques can reduce the recurrence of buckthorn after removal?
  • How much shade is needed to prevent buckthorn from thriving
Phase 2 (complete)

Project information

Research project title: Cover it Up! Using plants to control buckthorn: an expanded approach
Taxa: Plant
Species: Common buckthorn (Rhamnus cathartica)
Project status: Completed in 2023
Funding: $560,000

Research questions

  • What is the ability of slow-growing native perennial plants to suppress buckthorn?
  • How do deer and fire management interact with revegetation to strengthen buckthorn suppression?
  • What are the best methods to cost-effectively establish dense, suppressive shrub cover from seed?
  • Working with citizen scientists, what is the performance of revegetation seed mixtures in diverse environments across Minnesota?
Phase 3 (in progress)

Project information

Research project title: Managing buckthorn with trees: diversity, density, and practicality
Taxa: Plant
Species: Common buckthorn (Rhamnus cathartica)
Project status: In progress
Funding: $499,734

Research questions

  • What density of trees, shrubs, and herbaceous species is most effective at suppressing buckthorn regeneration?
  • What is the response of both buckthorn and native vegetation to these treatments?
  • What are the most cost-effective and practical methods for revegetation?

Practical implications

The outcomes of this research may provide affordable and practical solutions for land managers to establish native plant communities after buckthorn removal.


Reich and team developed strategies to improve and diversify the native plant community while discouraging buckthorn reestablishment. 

They defined buckthorn shade tolerance, and found that dense plantings of native grasses, wildflowers, sedges, ferns, shrubs, and juvenile trees (specifically those that provide heavy shade in spring and fall) can provide enough shade to suppress new buckthorn growth. Seeding woody species was more effective at creating rapid shade cover than bare root planting of the same species.

Researchers made a huge discovery regarding buckthorn seedbanks. They overturned long-held conventional wisdom that buckthorn seeds can persist in the soil for up to 6 years. Instead, they found that buckthorn seeds only survive in the soil for 1 to 2 years. This significantly decreases the resources needed to maintain a site after buckthorn has been removed.

This project team established an ongoing citizen science network to contribute to the research. Volunteer participants established 600 plots throughout Minnesota to evaluate how native seeding works to suppress buckthorn.

Parts of this research are currently in progress.

For related MITPPC research, see: Making revegetation as part of buckthorn management feasible in Minnesota.


Outreach and presentations

  • Prairie Enthusiasts Conference, 2024
  • Friends of Eden Prairie Parks, 2023
  • Using Plants to Control Common Buckthorn, webinar hosted by the Invasive Species Centre (2023, video)
  • Upper Midwest Invasive Species Conference, 2016, 2018, 2020, 2022
  • Legislative Citizen Commission on Minnesota Resources, 2022
  • ​​Minnesota Department of Natural Resources, 2021
  • CitSciVirtual Conference, 2021
  • Ecological Society of America, 2020
  • Minnesota Noxious Weed Advisory Board, 2020
  • Gathering Partners Conference, 2019
  • Duluth Cooperative Invasive Species Management Area, 2019
  • Duluth Invaders R2ED Team, 2019
  • UMN Undergraduate Research Symposium, 2018
  • St. Croix Research Rendezvous, 2018
  • Legislative-Citizen Committee on Minnesota Resources, 2018
  • Metropolitan State University Natural Sciences Seminar, 2018
  • MITPPC Buckthorn Symposium, 2017
  • Floodplain Forests Group, 2017

News and media

Project team

Peter Reich | principal investigator

Lee Frelich | co-principal investigator

Peter Wragg | post-doctoral associate

Michael Schuster | post-doctoral associate

Abbie Anderson | past citizen science coordinator

Kirsten Granstrom-Arndt | researcher

Artur Stefanski | researcher

Raimundo Bermudez Villanueva | researcher

Nicholas Partington | MS student, current citizen science coordinator

Andrew Kaul | post-doctoral associate


Lab or other website

The Cover It Up Project 


Collaborating organizations

Minnesota Department of Natural Resources

Friends of the Mississippi River

St. Croix Watershed Research Station


UMN Extensions

Three Rivers Park District

Ramsey County

Washington County