Save the Butterflies With DIY Milkweed Seed Bombs

CC BY 2.0. Herder3/Andrew C/KatherineSlade

Munitions to love! It's time to carpet the country with milkweed to give struggling monarchs a chance.

Got milkweed? Unfortunately for the monarch butterflies, North America has less and less of the herbaceous perennials of the genus Asclepias, which means fewer places for monarch moms to lay their eggs. Milkweed is the one and only host plant for monarch caterpillars and a rapid loss of habitat and milkweed has led to a precipitous drop in monarch populations. In just the last 20 years, the butterflies have declined by more than 90 percent.

There are a number of factors to blame, like land development and intensive farming, and especially the introduction of genetically modified soybeans and corn. Milkweed used to grow between rows of these crops across the country, but now herbicide resistant plants allow farmers to douse their fields with lethal things like Roundup, which makes mincemeat of milkweed. In the last 10 years, 100 million acres of monarch habitat has been lost thanks to the use of glyphosate tolerant corn and soybeans.

There are many organizations advocating for the planting of milkweed; if we’re responsible for eradicating milkweed, we better do our best to bring it back. One study concluded that "reducing the negative effects of host plant loss on the breeding grounds is the top conservation priority to slow or halt future population declines of monarch butterflies in North America." So let's get planting!

If you have garden space to plant it, great. You can start with seeds or cut straight to the chase and go with plugs. But those with no dirt of their own can do their part with some handy-dandy guerilla gardening and a handful of seed bombs. Seed bombs (or seed balls if you want to sound less militant) protect the seeds from scavengers and allow planting in hard-to-reach places. Abandoned lots, meadows, sides of the road, stream banks ... anywhere there’s soil within the reach of a good toss that could host some milkweed?


  • Seeds
  • Clay
  • Compost, potting soil, or seed-starting mix
  • Water

Sourcing milkweed seeds

Milkweed isn’t one species of plant, but rather 108 different species in the genus Asclepias; 73 of those species are native to the United States. It’s important to plant species that are as native to where you will be planting them as possible.

  • There are around 20 species that are available as seeds, the Xerces Society has an awesome search tool to help you find where to purchase appropriate seeds by state.
  • Also helpful, Biota of North America Program (BONAP) has a North American Plant Atlas that shows county-level distribution information for all Asclepias species in the lower 48.
  • And Monarch Joint Venture has this great fact sheet to help you find out which species to plant on a regional basis.
  • If you have milkweed growing locally, you can harvest seeds yourself – after you confirm that it is not tropical milkweed (Asclepias curassavica). This species has been inadvertently planted by many gardeners with the hope of providing monarch host plants, but it can actually do more harm than good in that it can infect the larvae with a crippling parasite.


    Seney Natural History Association/flickr / CC BY 2.0

    To collect your own seeds, like the ones above, find ripe pods that split upon touch; the seeds should be brown or getting there – seeds that are white or pale are not ready yet. Be careful with milkweed sap, it can hurt your eyes! Wear gloves and when handling the pods and keep your hands away from your face (and seek medical attention if sap gets in your eyes). Also, latex allergy sufferers should take care.


    Aside from seeds, you will need some type of clay that will act as the matrix for your bombs. There are many choices here:

    • Clay powder (available from art stores or sold especially for seed bombs)
    • Clay from an art supply store
    • Clay from the earth
    • Air-dry craft clay
    • Unused unscented clay kitty litter
    • Build the bombs

      The ratio is roughly:
      5 parts clay
      1 part compost/potting soil/seed-starting mix
      1 part seeds

      Combine the clay and compost; if you’re using wet clay you won’t need water, if you’re using a dry clay add water sparingly until it’s moist enough to stick together. Add the seeds, form into golf ball-sized balls, and set in a dry place to harden for a few days.

      And that’s it. Now arm yourself and find some good places to get some milkweed going. Some species can take a while to take hold and mature, but hopefully soon enough there will be new homes for monarch caterpillars to start their majestic caterpillar lives and go on to become some of the most remarkable insects on the planet.

      Here’s a video showing how one man makes milkweed seed bombs; the audio is a little wobbly – and he uses a 4-1-1 ratio, but he includes the pod fiber so it likely works out to be about the same.

      And finally, if you just want to get straight down to business, you can purchase milkweed seed balls already made. Bombs away!