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Research Highlights

Individual Highlight

Milking Milkweeds for More Monarch Butterfly Habitat

Photo of Milkweed plants are an important host species for both monarch larvae and adult butterflies. 
Milkweed plants are an important host species for both monarch larvae and adult butterflies.  Snapshot : Iconic monarch butterflies are disappearing from the landscape. They require milkweed plants to complete their life cycle. Milkweed seeds are often produced for restoration in nurseries in special beds. USDA Forest Service research shows that once these beds have served their purpose, milkweed taproots can be harvested, stored, and used for restoration, thus increasing the benefit of these beds.

Principal Investigators(s) :
Pinto, Jeremiah R. Dumroese, Kasten
Research Location : J. Herbert Stone Nursery, Central Point, OR and Moscow Forestry Sciences Lab, ID?
Research Station : Rocky Mountain Research Station (RMRS)
Year : 2019
Highlight ID : 1548


The rapid demise of monarch butterflies, whose larvae feed exclusively on milkweeds, is a serious concern to Canada, Mexico, and the United States. Scientists believe that loss of milkweeds to feed on is one main reason for the dramatic decrease in the monarch population. Thus, increasing the amount of milkweeds that can be produced to restore monarch habitat hinges on the ability to more efficiently produce more seeds and plants. Milkweeds grown in "seed increase beds" in nurseries provide large amounts of genetically appropriate seeds for specific projects. Once these projects are completed, the beds are often decommissioned and the plants are discarded. Milkweeds, however, have persistent, woody taproots that produce new shoots when plants are disturbed. USDA Forest Service researchers at the agency's Rocky Mountain Research Station wondered if these roots could be harvested, stored, and used in restoration projects, thereby maximizing the investment made in seed increase beds. They harvested taproots from a three-year-old seed increase bed and stored the taproots several ways during the winter. The following spring taproots were outplanted and evaluated for survival and growth. Taproots can be readily stored in cardboard boxes placed in either cooler (33–36 degrees Fahrenheit) or freezer (23–28 degrees Fahrenheit) conditions. Subsequent survival was as high as 90 percent with the addition of protection from the cold in the form of plastic bag liners and/or peat moss. By using cold storage, milkweed taproots can be harvested, stored, and outplanted at the proper time to produce viable and prolific plants for further restoration work and monarch habitat rehabilitation. Harvesting the taproots is an effective way to efficiently use all parts of the increase bed.

Forest Service Partners

External Partners

  • John Justin, J. Herbert Stone Nursery, Region 6, Central Point, Oregon
  • U.S. Bureau of Land Management
  • University of Idaho
  •  Native Plant Consulting, Medford, Oregon