How to Grow Milkweed for a Butterfly Garden

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Butterflies, and particularly the monarch butterfly, love milkweed. Yet for many decades farmers and homeowners both considered this wildflower to be a weed that needed to be killed, directly leading to the decline of the monarch butterfly population. More awareness about how necessary milkweed is to the monarch life cycle has helped change this flower’s description from weed to wonderful, and helped turn around the threatened monarch population.

A female monarch butterfly will lay three to four hundred eggs on the leaves of milkweed plants, which is the sole food of their larvae. Once hatched, the caterpillars will increase their body mass more than two thousand times before forming a chrysalis or cocoon. After about two weeks, the adult butterfly will emerge.

The most amazing thing about this adult butterfly is how its individual life fits into the epic annual migration of the species. Each winter, the monarchs overwinter in southern climes – some in California but most in Mexico. Come spring, these butterflies will travel north for a few hundred miles, looking for a good patch of milkweed for their eggs and other flowers’ nectar for themselves.

Their own life span will run short at this time, but their offspring – once they’ve hatched, eaten lots of milkweed, and metamorphosed into adults – will travel another few hundred miles before repeating the process. Four or five generations will pass during the spring and summer until the final generation of adults for the year emerge in Canada. Then these newest adults will ride the air currents all the way back to Mexico – around 3000 miles – to the same exact trees where their ancestors have always overwintered, where they will live until they travel north again in spring to create the next generation.

You can help these majestic butterflies, as well as more sedentary local species of butterflies, bees and other beneficial insects, by planting milkweed in your garden. Our Save the Monarch Kits are customized for each region of the U.S. to provide milkweed and other butterfly-friendly wildflowers native to that area.

Tips to Successfully Growing Milkweed

  • You should plant your milkweed in an area that receives full sun.
  • Plant out of the direct path of foot traffic to protect any baby monarchs that will live there.
  • If you’ll be planting them in an area that is very weedy, you should till, mow or harrow the site first to prevent the weeds from out-competing the seedlings.
  • Planting in the spring? You may want to put them in your refrigerator inside a sealed plastic bag for 3-6 weeks, or in the freezer for a day or two followed by a day of thawing. This will help trigger the germination process when you plant them by mimicking the winter they didn’t experience in your garden. Or you can skip this process by planting in the fall and letting nature chill the seeds for you. Wait until the danger of frost has passed.
  • Planting in the fall? Plant before the ground freezes but after the first killing frost, so they don’t accidentally sprout too soon.

Planting from Seed

When it’s time to plant, mix the seeds with ten times as much vermiculite, rice hulls or sand to make it easier to broadcast evenly. Loosen the top two inches of the soil where you will be planting. A 1/8 lb kit will cover about 500 square feet. Broadcast the seed mixture, then tamp down the soil.

Lightly cover the area with compost or straw, but be careful not to bury the seeds too deeply or they will not sprout.  Aim for 1/8 inch depth, and no more than 1/4 inch. You will need to irrigate the seeds for at least four to six weeks while they germinate, and another time or two in the dry season, but they will naturalize once they reseed and take root with the winter rains in subsequent years.

You may need to supplement the area with more seeds the next year as your patch gets established. If the site where you planted them gets limited water, or has erosion or weed problems, you may need to plant again in future years as well.

Other Things to Consider About Milkweed

  • Some varieties can be invasive. Common milkweed (Asclepias syriaca) and Showy milkweed (Asclepias speciosa) can spread through underground rhizomes. So if you have limited space you may want to avoid these varieties.
  • Milkweed is poisonous to animals if browsed, so plant it away from areas with livestock or a pet run.
  • Milkweed will ooze out a “milk” that can cause eye damage if it finds its way into an eye.
  • Monarchs have an easier time finding your milkweed if you plant more than one plant.

How to Collect Seeds from the Milkweed Pods

  • Don’t collect too early. If you open up the pod and the seeds are light brown or even white, they will not be viable for planting the next season.
  • Collect the seeds before the pod opens up. So one way to avoid them bursting open is to put a rubber band around the pod (not wrapped too tight, just loosely).
  • You know the pod is ready to collect when you squeeze it and the center seam makes a popping sound.
  • You will want to remove the seeds from the floss or fluff. Start from the pointed end, grab that end and pull it out of the pod. Keep holding the center section and knock the seeds off as you hold the floss.
  • If the pods have already popped and the fluff is coming out, simply collect it (with the seeds attached), put it into a paper bag with a few pennies. Close and shake the bag. This will separate the seeds from the fluff.
  • If you are not planning on planting until the following spring, you can store the dry seeds in a paper bag, plastic bag or jar. Place in the refrigerator until ready for use.

Check out the Monarch Watch website. It has great information on monarchs and how to create a Monarch Waystation. Grow some milkweed and flowers for nectar, and grow organic for life!