Milkweed Seed Success


Waiting for spring to come?  Here’s a project you can start indoors now that will bring butterflies to your yard in warm weather.

The caterpillars that become monarch butterflies eat only milkweed leaves.  The number of monarch butterflies has gone down a lot in recent years, so many people are planting milkweed seeds to help the butterflies.

There are many kinds of milkweed.  Three that you can usually find in the Chicago area are common milkweed, swamp milkweed, and butterfly weed.

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The easiest time to plant milkweed is in the fall.  If you made a seed bomb at our Marvelous Mariposas program and planted it that night, then all you need to do is watch for leaves.


If you saved your seed bomb, or found some milkweed seeds this spring, then there are a couple of extra steps to take.  The seeds need a signal that winter is over and it is safe to start growing.  If the seeds have been sitting indoors all winter, that means that they need to spend time chilling as if they had been freezing outside.

To chill your seeds, wet a paper towel and wring it out. Spread your seeds on one half of the damp paper towel. Fold the empty half of the paper towel over the seeds to cover them. Put the seeds and paper towel inside a plastic bag. Keep the bag in the refrigerator for 4 to 6 weeks. You can plant the seeds once the danger of frost is over, around May 15.

If you’re trying to decide what kind of milkweed to plant and where to plant it, here are a couple of things to consider.

All milkweed plants need plenty of sunlight.  The big differences between common milkweed, swamp milkweed, and butterfly weed are their height and the types of soil they like.

Common milkweed (Asclepias syriaca) is the least fussy about its soil.  This is the type that you are most likely to see in the wild and the type that is mostly likely to “volunteer” in your yard.  In terms of looks, it is the tallest (typically 3 to 5 feet and up to 8 feet) but its flowers are not as brightly colored as swamp milkweed or butterfly weed.  It blooms between May and August.

Asclepias incarnata or swamp milkweed, as you would expect from the name, likes soil that is damp most of the time.  It is 2 to 5 feet tall and can have bright pink flowers.  You can sometimes find plants for sale in garden centers.  It blooms in late summer and early fall.

Butterfly weed (Asclepias tuberosa) is much shorter than the other two at only 1 to 2 feet tall and has orange flowers.  It likes well-drained sandy or loamy soil and it blooms between May and September.  Seeds are relatively easy to find for sale.  Its pods are long and skinny, like this:


Save the Monarchs Bolingbrook has made free seed packets available at Village Hall (while supplies last), and I have had luck in the past asking the Bolingbrook Park District for permission to gather seeds near Hidden Oaks.  Seed pods for common milkweed are rounder, and this time of year have usually faded from green to gray:


Websites like,, and have more detailed information on creating a yard or garden that is butterfly-friendly.  In addition to planting milkweed, some other steps you can take are planting flowers with nectar to feed adult butterflies and avoiding pesticides that can harm these insects.  We will also be happy to help you find gardening books, butterfly books, and other resources at the library!





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