Sowing Milkweed Seeds

Growing milkweed (Asclepias sp.) from seed doesn’t have to be mysterious or complicated. In this post I’m focusing on sowing milkweed species native to eastern North America, which generally require (or at least benefit from) a cool, moist treatment known as stratification.

A container with one inch of perlite on top of seed raising mix

If you’re wondering what the white snow-like stuff in the above photo is, read my post on sowing seeds in perlite to understand how it can increase your success with seed propagation.

Sowing the seed
The biggest mistake I still sometimes make when sowing seeds is spreading them too thickly. If you have a lot of seeds, make a conscience effort not to sow them all, or at least spread them over two or more containers. If not, a whole host of problems will arise – from poor air circulation around seedlings, to crowding out each other – making it very frustrating to transplant.

Sowing milkweed seeds on top of perlite

When sowing seed I like to use a folded piece of paper to slowly spread the seeds out. You’ll notice that they aren’t all evenly spaced. This is less of an issue than having too many seeds in the container.

Covering the seeds with a thin layer of perlite

Covering the Seed
Lightly cover the seeds with perlite; this keeps them in place and prevents the light seed from blowing out. Also, label each container with the plant name, date, and other information of interest that can be easily forgotten over time.

Soak the seed pot in a dish of water

Soak the container in a dish of water until it is thoroughly wet. I usually let it sit in water for an hour or two then test it by picking it up to make sure it is heavy and saturated with water. Let the excess water drain out, then place in a plastic bag to keep it from prematurely drying out and help prevent any animal disturbance.

Container enclosed in plastic bag to prevent seeds from drying out

Where do I put my seeds until they germinate?
Option 1 – seeds sown in spring through early summer
Placing the container in the fridge for 3 weeks. Longer won’t hurt, but check periodically (if longer than 3 weeks), as seeds can sometimes start to germinate in the fridge. Once the seeds are taken out of the fridge and the temperature is consistently above 75 °F, germination usually occurs in one to three weeks.

Option 2 – seeds sown in mid-summer
Depending on what climatic zone you live in, it may be too late to place seeds in the fridge, wait for germination, and get plants established before winter. If seeds are sown, but not stratified in the fridge, most species will wait until the following spring to germination, though some southern species like Asclepias humistrata, Asclepias lanceolata, and Asclepias rubra may go ahead and germinate without having a stratification period.

Option 3 – seeds sown between late summer and late winter
Seeds will germinate next spring. Keep outside away from direct sunlight and try not to let the container freeze solid for extended periods through the winter.

In the next post learn how to take care of milkweed seedlings once the seeds germinate.


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