How to Grow Swamp Milkweed from Seed

A quick note- Milkweed seeds can take a couple of seasons to grow into a decent sized plant. The first year it might remain quite small. It’s a good idea to mark it with a stake or label of some kind to help you keep track of where you planted the seeds.

Germinating Swamp Milkweed Seeds

Like most milkweeds, Swamp milkweed/Asclepias incarnata requires at least 30 days of cold stratification before it will germinate. Cold stratification is the process of exposing the seed to cold and moist conditions to break dormancy.

The easiest way to do this is to plant your seeds outdoors in the fall. Make sure you mark the spot somehow, so you know where you put them. Otherwise, they may look like weeds when they start growing. The plants easily handle being moved, so you can even start them in a pot, or a seed flat outside and then plant them once the roots have established in the spring.

 You can also cold-stratify indoors by placing the seeds in moist sand, moist vermiculite, moist coffee filter, etc, in a resealable plastic bag in the refrigerator. There is a lot of information online about cold-stratification if you would like to research it further.

Swamp Milkweed Seed Pod

Swamp milkweed produces plenty of seeds for you to share or start new plants. Collect the seed in late summer/fall just as the elongated seed pod is starting to split open but before the white “fluff” starts to float out. At this stage it is pretty easy to strip the seeds off the white silky threads that will soon fluff up and allow the seed to float off in the wind.

Herbaceous perennial

Hardy in USDA zones 3-8

Full to partial sun

Moist soil (though will grow in clay and less moist soils with ample watering. Also does well in pots).

Clusters of small pink flowers bloom throughout the summer

2-6 feet tall

Space plants 1 1/2 – 2 feet apart