I’ve long since learned the value of milkweed plants to monarch populations. They are the only larval host plant where monarch butterflies will lay eggs, and a food source for those hungry monarch caterpillars. The variety I’d stumble across as a child would have been Common milkweed, ubiquitous in sunny areas at the edge of forests, throughout hydro corridors, and along roadsides. For many years, those growing locales were in decline. And Common milkweed was once on my province’s noxious weeds list! Luckily it’s since been removed, as the importance of growing milkweed for the monarch species’ survival has been so well conveyed to the public.
North America is home to over 100 species of milkweed, but only about a quarter of them have been identified as being host plants for monarch butterflies. If you’d like to plant your own milkweed seeds, the best thing you can do is source the pods from the area in which you live. Check with your local environmental or monarch organizations to see if you can find any documentation and photos of milkweed that commonly grow in your region.
Identifying milkweed pods
Three milkweeds that are prevalent throughout North America are Butterfly weed (Asclepias tuberosa), common milkweed (Asclepias syriaca), and swamp milkweed (Asclepias incarnata).
Common milkweed is probably the easiest to find. Just look for a dry area, like a ditch. Where I live, I see it along my local rail trail, and at the sunny edges of forests where I mountain bike. The pods are pretty easy to spot in a landscape, especially towards the fall as other plants die back. It’s hard to describe the shape of the pods, but they’re basically conical or horn-shaped (but the cone part is at both ends). The pods are usually pointing upwards.
If you’re going to forage, it’s important that you don’t take milkweed pods from someone’s property without asking first. (Trust me, I’ve been tempted!) They may be saving those pods for their own garden. And as is common practice with any foraging, don’t take all the pods from one area. Leave some pods to naturally open and reseed themselves.
How do you know milkweed pods are ready to pick?
Milkweed pods are usually ready to pick in late summer, into early October and even November. And they don’t all ripen at once! To collect seeds, it’s easier if you get to the pods before they split. The seed pod will start to dry out, eventually splitting open on its own. While some pods may start to turn brown, a milkweed pod could still be green, but be ready to harvest.
If the center seam pops open from gentle pressure, the pod is ready to pick. If it doesn’t open by pressing gently, it’s not yet ready.
Ripe seeds are brown in color. White, cream, or pale-colored seeds are not ready to be harvested.
What to do with your milkweed pods
Once you’ve pried open the pod, grab the center stalk from the pointed end, and gently tear it away. You may want to hold your pod over a container to catch any extra seeds. Holding the end of that stalk, you can gently pull the seeds off the milkweed silk. Slide your thumb down as you go, so the silk doesn’t come loose.
If you’re not going to collect seeds from your pods right away, avoid leaving them wet in plastic bags. Unwanted moisture can lead to mold. Separate the seeds as soon as possible.
There are other ways to remove the seeds from the silk that involve vacuums and DIY contraptions (you can find info on the Xerces Society website). Another recommendation if you find a milkweed pod that’s split, is to put the fluff and seeds in a paper bag with a few coins. Give the bag a good shake. Then, snip a hole in the corner of the bottom of the bag to pour out the seeds.
Some milkweed pods can hold over 200 seeds inside!
There are three things you can do with milkweed pods that are ready to harvest:
- Leave them on the plant and let nature do its thing
- Open the pods and scatter the seeds in the late fall
- Save the seeds to plant in the winter
Storing milkweed seeds
To store your seeds, make sure they are completely dry. Then, put them into a sealed jar or Ziploc bag in the refrigerator until winter when you’re ready to plant them.
Jessica’s article on how to grow perennial milkweeds from seed provides all the details for late autumn or early winter sowing.
Milkweed pests that damage the seeds
There are a few insect pests that enjoy milkweed, such as the large milkweed bug (Oncopeltus fasciatus) and the small milkweed bug aka common milkweed bug (Lygaeus kalmia). The nymphs have a needle-like mouthpart that pierces the milkweed pod, and sucks the juice out of the seed, rendering them un-plantable.
Adult red milkweed beetles (Tetraopes tetrophthalmus) are herbivores, feeding on the leaves, stems, and seed pods of milkweed plants.
Don’t worry about eliminating them all. In fact it’s recommended that you leave milkweed bugs be as part of your local eco-system. Try planting more milkweed throughout different parts of your garden to provide more food.
Another threat to milkweed plants is the Japanese beetle (Popilla japonica). They feed on the flowers, preventing the plants from forming seedheads at the end of the season. If you see these insects on your milkweeds, a bucket of soapy water will take care of them.
For more information about attracting butterflies to your garden, read and watch:
- How to collect butterfly weed seeds
- Butterfly host plants: How to provide food for young caterpillars
- Young monarch caterpillars on milkweed
- Plant a caterpillar garden
- Pollinator garden design: How to get started attracting bees, butterflies, and birds
