Swamp milkweed seed cold stratification

Asked September 29, 2020, 2:10 PM EDT

I collected the seeds from my swamp milkweed to give away to local gardeners/neighbors (to help monarchs). How long do the seeds need to cold stratify? Ninety days? I read that you’re supposed to plant them in the late fall, but I can’t find an exact period of time. Is our area cold enough for that?

If someone wanted to cold stratify them in their refrigerator, I would like to be able to advise them.

Thank you.

Harnett County North Carolina

2 Responses

Hello and thank you for your question!

You are absolutely right in that milkweed needs cold stratification, and luckily for us here in the Harnett County area, we usually do get cold enough to meet those requirements. You will need 30 days minimum for cold stratification, but you could go up to 6 weeks in a cool refrigerator. Of course, leaving them outside for the winter will do the trick, too.

If you have other questions about milkweed/stratification, don't hesitate to reach out at sdmckoy@ncsu.edu.

You can find more info on cold stratification at these links:

Hi Selena,
It’s great to hear from you, as always.

Thank you for your response.

One more question - after cold stratification, do they need to be planted right away? If those links addressed it, I overlooked it.

Thank you.