Harvesting milkweed seeds is all about timing. If it is too early, the seeds are not yet mature and will not germinate. If it’s too late, the entire plant will have been blown away or created a messy web of white fluff (called milkweed cotton or milkweed silk).
In late summer, you can often see milkweed pods ripening in weed-filled fields or along the edges of trails you hike or bike. This is how I gathered my first stash of milkweed seeds so I could grow milkweed at home. (If you want to do the same, make sure it’s allowed first and leave some pods on the plant to spread naturally.)
The seed pods of different species of milkweed are slightly different, but they have a similar teardrop shape with a pointed tip. Although several types of milkweed are native to North America, three types of milkweed are commonly found in the wild:
Milkweed (Asclepias syriaca) has thick, spiny seed pods. Butterfly weed (Asclepias tuberosa) and swamp milkweed (Asclepias incarnata) both have narrow, smooth seed pods
However, once you know a few tricks to cleanly separate the seeds from milkweed fluff, the process for picking and processing them is the same for all. You’ll be able to do it in just a few seconds.
So how do you know when milkweed pods are ready to pick?
Milkweed pods mature as they begin to dry out in August-September. However, it doesn’t have to be completely dry and brown. Squeeze the slightly green pod and when the seam pops open, it’s ready.
Seeds should be dark brown and leathery. (If it is cream, very pale, or white, it is immature and will not grow as a plant.)
quick tips
Sometimes you can find milkweed insects crawling on the seed pods. These red and black insects eat the seeds by boring holes into the pods and injecting digestive enzymes to liquefy the seeds. If the seed pods are covered in milkweed bugs, the seeds are likely damaged.
Method #1
The key to easy harvesting is to pick the seed pods before the fluff inside expands and the pod bursts.
Select an unopened seed pod and apply gentle pressure to the seam. If it doesn’t open easily, the seeds inside are immature. Once the pod is open, it is very easy to separate the seeds from the fluff.
Pinch the seed clump at one end of the pod and pull the seeds out with your other hand. (This is like peeling the leaves off an herb twig.) The seeds should fall out easily, leaving behind a “cob” or cone of milkweed cotton, which can be discarded.
Method #2
If you take a chance and the milkweed fluff is flying everywhere, the best way to separate the seeds from the fluff is to shake it out.
Place milkweed floss and seeds (or whole open pods) in a jar along with a few coins. Shake vigorously. The coin does all the work of separating the fluff and seeds.
The seeds will sink to the bottom of the jar, so you only need to lift out all the fluff. (If you’re handy, you can recycle milkweed fluff as stuffing.) If you don’t have a jar on hand, a paper bag will work just as well.
Seed storage
Once you have collected all the seeds, store them between damp paper towels in a sealed jar or ziplock bag in the refrigerator for at least 6 weeks. You can store them in the refrigerator until you are ready to sow them in the spring. (During the winter, check regularly and keep it slightly damp by spraying it with a paper towel, but be careful not to get it soaked.)
Why a refrigerator? This is because milkweed seeds must be exposed to very cold weather (called cold stratification) for a period of time in order to germinate. (This is one of the most common mistakes made by people who wonder why their seeds don’t germinate.)
If you don’t want to bother with storage, you can also scatter milkweed seeds in place in the fall or winter and let Mother Nature do the stratification.
