Saving Common Milkweed Seed

by Maureen Hark, Growing West SideIMG_3981One of the most important plants for Monarch Butterflies is Common Milkweed (Asclepias syriaca). The butterflies lay their eggs on the undersides of the Common Milkweed leaves. The hatched caterpillars will live their entire life on the plant, eating the leaves and eventually developing into a chrysalis. In order to survive, the Monarch needs a healthy supply of milkweed and is completely dependent on us to see that it continues to be available to them.










Common Milkweed as it looks in early September. The leaves are green are healthy with some just starting to turn yellow. The seed pods are full.


When to Collect Seeds 

The time to start looking for common milkweed pods is now. Go out and see if you already have some growing in your garden. If not, look around the neighborhood, but be sure you get permission from who’s ever yard you find them in before you make plans to harvest.

What to Look For                        

You will be looking for pods that are with in a day or two of opening up and contain mature brown seeds. The closer to maturity the seeds are the easier they crack open when gently pinched. Pale or white seeds should not be collected as they are not fully mature and most likely will not germinate when planted


It is best to wait until seeds are completely brown (fully mature) before harvesting to increase the chances of having viable seed.


The seeds on the left are still white and not mature enough for harvest. The seeds on the right have just begun to turn brown.




The trick is to get the seeds as soon as they are mature but before the pod fully opens up and they are blown away by collection window.the wind. If it is hard to visit the plants on a regular basis to check if they are ready to harvest, you could try putting netting over the pods, or a rubber band around the widest part of the pod to hold the seeds in. This will extend the collection window.






Almost any kind of netting will work. Here a cast off onion bag was cut in half and slipped over the top of a group of pods. The netting contracted around the pods and did not need to be tied on.

Harvesting the Pods and Separating the Seeds from the Fluff

To harvest the pods, gently pull or cut off the plant. Dry the freshly collected pods in a place where there is good air circulation until they are completely dry.

To separate the seeds from the fluff, open the pods and scrape the contents into a paper bag. Shake the bag vigorously to separate the seeds then cut a small hole in the corner of the bottom of the bag and shake out the seeds into a bowl. Or put the seeds and fluff into a plastic container with a tight fitting lid with several coins. Put the lid on tightly and shake. The coins will help separate the seeds from the fluff and they will fall to the bottom of the container.


Labeling and Storing the Seeds

Put the cleaned seeds in an envelope or small paper bag that can be sealed. Label the package of seeds with the type of seed, date you harvested and the location where it was collected. Store the seeds in a cool, dark dry place till you are ready to plant.


Sharing the Seeds with the GWS Seed Library

Bring your extra seeds in marked packages to the Riverview Library and turn them in at the front desk. The Librarians will see that they are given to the Growing West Side Seed Library for distribution in the neighborhood.

Important Things to Know about Milkweed and Seed Collection

Milkweed Sap/Latex allergy

Milkweed sap can irritate your skin, especially if you have an allergy to latex. Be sure to wear gloves when working with the pods. Avoid touching your face. The sap can be damaging to your eyes and the effects from the sap do not always show up right away. Be especially careful if harvesting the seeds with children.

Milkweed Bugs

Milkweed bugs are not harmful to Monarch larvae or milkweed plants but they do feed on the seeds. The damage is difficult to see but the seeds will not germinate if they have been pierced by the milkweed bug. When collecting milkweed seeds, pass by those plants that have milkweed bugs present. This will increase your chance of collecting viable seeds.

Online Resources

Harvesting Milkweed Seeds                                                                                   

Milk Weed Bugs

For a photo identifying Milkweed bugs, go to:


Maureen Hark, Growing West Side 9/2015