As the leaves continue to fall, the fluffy, seed-carrying parachutes of the milkweed flower are hitting the air. Now is the perfect time and in some places, the last chance to gather seeds from our several native milkweed species. Not only is it a great time to collect these and other native wildflower seeds, it is also a great time to sow them for next year’s growing season.
Milkweeds are from the genus Asclepias and all contain a milky latex sap which contains toxins that deter herbivores from eating them. But specialized insects, like the Monarch Butterfly, have co-evolved with this plant. Milkweed is the sole food source of Monarch caterpillars and by eating leaves, they incorporate the toxins into their bodies to prevent predation. Several other bees and butterflies will drink milkweed flower nectar, but the Monarch needs milkweed in order to complete its life cycle.
Ontario has 4 milkweed species that can be grown and added to the garden:
Common milkweed (Asclepias syriaca)
Swamp milkweed (Asclepias incarnata)
Butterfly milkweed (Asclepias tuberosa)
Poke millkweed (Asclepias exaltata)
This time of year, the various milkweeds have formed pods full of seeds. Although the best time to harvest the seed is when the pods are brown and dry (in terms of ripeness), it can be difficult to get the timing right and the seed can float away on a dry, warm and windy day.
Therefore, consider harvesting when the pods are still yellow or green but just beginning to split open. Seed can be immediately removed from the pods and pulled from the fuzzy pappus with little trouble (much more time consuming and perhaps not worthwhile to clean off the pappus if it has been allowed to dry and fluff out). Take the seed and leave it spread out on a plate in a warm, dry place to dry further for a week or so and then it is ready to plant.
It may seem strange to sow seeds now as the weather is getting colder, but it is actually the perfect time for many of our native species. With the historically cold winters in Hamilton, several of our native species’ seed need a period of cold in order to germinate. Sowing them in fall, in trays that are left outdoors to experience freeze and thaw conditions, replicates what happens to the seed in natural conditions.
Simply sow milkweed seeds near the surface, with a light covering of potting mix and sand (which helps hold down soil), in a container with drainage holes and place outside in a place where the container can get rain and snow on it. It is highly recommended to also put chickwire over the container or place it in an enclosure that squirrels cannot access (or use hardwire cloth to keep out mice if that is a concern). As the soil warms up in spring, the milkweed will sprout and once it has a few sets of true leaves, it can be potted up. It may be tempting to sow the seed directly into the garden, but unless you know what the baby seedlings look like, it is easier to sow in a container where you can easily assess if they germinated or not (vs. confusing them for other seedlings from weeds etc).
A quicker, but more intensive way to also germinate milkweed is to place the seeds in a slightly dampened paper towel inside a plastic bag or container and seal it up. Put this container in the fridge for 30 days and then sow the seeds into potting mix and place in a warm, sunny location. Don’t forget the seeds in the fridge though because they will germinate in the fridge and die if not planted in time.
With either sowing method, don’t forget to label the pots! At Green Venture, we put a tag on the tray and in the tray for all of our outdoor sowings just in case.
Common and Butterfly milkweed prefer full sun and can take drier soil conditions. Swamp and Poke milkweed can take partial sun conditions and prefer moister soil. Therefore, there is a milkweed for almost any garden condition, except deep shade.
At the Hamilton Seed Libraries, we are currently stocked at all of our library locations with Swamp and Common milkweed seeds in case you are unable to collect your own seed this fall. Consider also sharing any extra seed at these sites, especially other milkweeds and native wildflowers this fall. Make sure the seed is labeled in individual envelopes, easy for people to read and take home.
To learn more about this amazing, unique native plant, the role it plays in Monarch butterfly lives, and about growing native plants from seed, check out these other resources:
https://www.xerces.org/milkweed
https://www.rbg.ca/growing-milkweed-in-ontario/
https://davidsuzuki.org/take-action/act-locally/butterflyway/
https://nanps.org/nanps-seed-exchange/
https://wildseedproject.net/how-to-grow-natives-from-seed/
