Starting Milkweed from Seed
We offer Common Milkweed, Asclepias syriaca, in an Art Pack designed by Nancy Blum, to help raise awareness about the Monarch, their habitat, and what we can all do to help ease the threat placed on Monarch populations due to loss of habitat.
While it is certainly true that modern agriculture and industry are responsible in a large part to the loss of habitat for monarch larva, simply having a garden, lawn, or field which is mowed down, tidy and weed free, and therefore free of milkweed, contributes.
Monarch butterflies lay their eggs exclusively on members of the Asclepias genius. These plants serve as the sole source of food for the larva. The bitterness of milkweed is from the glycosides present in the milky latex, which are the compounds that make monarch butterflies and larva toxic to predators. (These compounds are toxic to humans too.) While there are several species of Milkweed, Common Milkweed is usually most associated as "Milkweed." It is native to the the Eastern US, and is the best milkweed to plant in the eastern states.
As you might notice, the seeds from the milkweed flower disperse in the fall. Attached to pappi, the silky threads that catch the wind, they disperse from the pods and travel in the wind before landing on the ground. The winter temperatures, snow, and freeze thaw cycle "plant" the milkweed, and break the seed down enough to allow it to germinate in the spring.
When starting seed from a native plant purposefully, it's always a good idea to mimic how it would germinate in it's native habitat.
There are 2 methods, each can be done in the the fall or in the spring.
Method 1: In Fall--Sowing in containers
Pros: By keeping the milkweed contained, the milkweed seedlings are able to grow big and healthy before transplanting. In order to get well established and come back year after year, the plant should grow to about 24" high, allowing it to form a healthy rhizome, which it needs to overwinter. If the leaves get munched off by caterpillars while still small, the milkweed won't be able to establish a healthy root system and might not survive the winter.
Cons: The added time in caring for plants in containers, plus the transplanting time in the early summer.
How to start: Fill 4-6" plastic pots with a well-drained potting mix. Sow 5-10 seeds per pot, spacing them evenly, about 1/4 inch deep. Press in, and water well. Place the pots outdoors, on a porch or at the side of a house is ideal, and leave them there to weather the winter. In the spring, as the temperatures warm, the pots should be moved into full sun to a protected spot and allowed to germinate.
Method 2: In Fall--Direct sowing into prepared garden plot
Pros: The ease of this method is the most attractive! It is also the most similar to how milkweed is propagated in it's natural habitat.
Cons: To execute this method, you will need to plan out the location of your patch in the fall, when most garden chores have ended. The seedlings will also be susceptible to pests and perhaps even hungry caterpillars, which can keep them from establishing themselves to survive over the winter.
Method 3: In Spring--Sowing in containers
This method is almost identical to method 1, except you will need to vernalize the seeds. Eight weeks prior to your last spring frost, start seeds in pots as directed. Water them in well, then, cover with plastic wrap and place in a refrigerator for 2-4 weeks. Then, proceed as above. (You can also start the seeds in cell trays, but this method in larger posts is preferable because the root systems have the room to develop.)
Method 4: In Spring--Direct sowing into prepared garden plot
This method is almost identical to Method 2, except you will sow the seeds in early spring, when night time temperatures are still in the 30's. The seeds can be sown later, though you might see decreased germination as the weather warms.