Milkweed Adaptation

Got Milkweed? Research and Teaching About Local Adaptation in Common Milkweed 

Contact: Professor Emily Mohl, 

Monarch caterpillars only eat one kind of plant–milkweed. As monarch butterfly populations are declining and more people are planting milkweed, what is important to understand about this food source?

This project investigates local adaptation in common milkweed, Asclepias syriaca, one of the most important food sources for monarchs. In particular, we ask whether local populations of milkweeds outperform nonlocal populations.  Alternatively, certain populations may outperform other populations everywhere.  Understanding these patterns should help us make better decisions about how to manage and plant milkweed populations.

We invite educators and students to participate in this investigation through a distributed research model.  Our goal is to involve participating institutions, distributed across the range of common milkweed, in both teaching and research.

Two levels of participation are possible.

Both Level 1 and Level 2 Participants will follow protocols to:

  • Collect Seeds from, and take measurements on plants in, naturally occurring local populations of Asclepias syriaca (common milkweed) in the fall of 2017.
  • Send their seeds to St. Olaf college for processing

Researchers will process and redistribute seeds to Level 2 participants, who commit to follow protocols to:

  • Germinate seeds and establish one or more experimental plots with about 20 milkweed plants
    • Experimental plots do NOT have to be at the same site where seeds were collected.
    • Experimental plots will include 5 plants from your local population and ~3 nonlocal populations, for a total of 20 plants.
  • Measure and record data on milkweed growth and herbivory annually in the spring and fall (and optionally through the summer) for at least 3 years.
  • Submit data


Requirements for participation:

  • A commitment to follow protocols carefully without modifications, and to ask as you have questions.
  • Local naturally-occurring source of common milkweed seeds
    • Try to find a site with ≥5 stems (with pods) that are ≥5 meters apart

Level 2 participants also require:

  • A minimum of 20 square meters in which to plant common milkweed at a site accessible to students.
  • The ability to grow and care for seedlings during spring and summer of planting
  • Materials for germinating seeds, plant seedlings and measuring plant growth.
    • potting soil, pots, meter stick, calipers
  • A commitment to collect and submit data in the spring and fall for at least 3 years.

All participants are eligible to access datasets for use in their classes and potentially for publication.  Level 2 participants are eligible for coauthorship on resulting publications.


The map below shows the distribution of current participants.  We would love to have more participants distributed throughout the native range of common milkweed, especially in New England and the Midwest.

We are developing a series of lesson plans to motivate the project and support student learning in connection with the Next Generation Science Standards.  They are shared with project participants and available to others on request.

Lesson Theme Activities
1. Monarchs and their Decline Introduction to monarch life cycle and population decline Brainstorming, role playing
2. Monarch Population Decline Debate Multiple hypotheses for population decline Read research article, guided debate
3. Milkweed Milkweed traits and measurements Stations to learn about milkweed, discuss the lab
4. Evolutionary Principles Learn/review evolutionary processes, connect to predictions about milkweed adaptation Guided worksheet with video, vocab review, identify questions/predictions for lab
5. Data Analysis Using data to answer questions/test predictions Data entry, visualize and interpret data
6. Applying Local Adaptation Apply learning: is it risky to plant non-local milkweed? Evaluate risks, scientific argumentation
7. Citizen Science Share arguments and evidence with the community Data jam