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Managing Asclepias Plants: How To Control Spreading

by Amanda

blooming asclepias plants

Perennial asclepias plants, also known as butterfly weed, are an integral plant to the survival of pollinators, especially monarch butterflies. But if you let certain varieties of asclepias do their own thing without managing the plants, in several seasons you’ll have an entire garden or meadow full of these native beauties. Depending on who you ask, this could be a good or bad thing – the pollinators sure love it, but some (though not all) asclepias can quickly choke other plants out.

Asclepias is also known as Milkweed. The Asclepias family includes Butterfly Weed, Common Milkweed, Swamp Milkweed, Whorled Milkweed, Prairie Milkweed, and more.

The good news is there are very simple steps to managing asclepias plants in the fall that will help control them from spreading. Bonus: you can plant the seeds on another part of your property, or give them to a lucky gardening friend.

asclepias plants ready to harvest
This seed pod is at the perfect stage to either cut or tie up to prevent the asclepias seeds from spreading in the wind.

Cold Stratification

Asclepias seeds need to go through a cold stratification process in order to grow in the spring. This wintertime act of freezing, thawing, swelling and shrinking is necessary for these seeds to successfully crack open and germinate. This means that you still have time in the fall to control the spread of the seed.

You can either harvest the seeds and store them in the fridge or tie the pods up with string or a rubber band (to prevent the seeds from dropping) and let them cold stratify outside in the winter.

Tying Up Seed Pods From Asclepias Plants

If you’re looking to prevent the seed pods from opening up and dropping seeds in the fall, but aren’t ready to harvest, simply tie string or a rubber band around the center of the pods. The key to this is to get to them before they open up, which should be in mid to late October, depending on your region. By the time I got to my meadow many of the pods had already opened up, but I was still able to tie several that hadn’t. I’m not too worried about it as I love my field of asclepias and have the space for it.

tying up asclepias plants
Even though many of my seed pods had already opened up, I was able to tie up several that hadn't yet.

You can then leave the pods tied up until the early spring, which lets the cold weather naturally stratify the seeds on the stalks. In early spring you can harvest the pods as normal and either plant the seeds immediately or give the pods away to a friend.

Harvesting Seeds From Asclepias Plants

If you have space in your refrigerator, or know someone who wants to plant the seeds immediately in the fall, you can harvest the asclepias seeds in mid to late October to prevent them from spreading. Again, you’ll want to do this once the temperatures have dropped but the seed pods haven’t quite opened up yet.

harvesting asclepias plants
I quickly cut this pod off before the seed had a chance to drop.

Simply cut the pods off the plants and bring them indoors. If some of the pods have already matured and are ready to open up, you’ll have the (slightly) challenging task of separating the seeds from the seed hairs, which are extremely fluffy and fly everywhere. I actually found it to be quite fun and so did my dogs, who chased the seed hairs around the screened porch.

removing seeds from asclepias plants
Ready for harvesting, seed hairs and all!

Once you’ve opened up the pods and separated the seed into a bowl, you can give them away to plant in the fall (nature will naturally stratify the seed) or you can stratify them yourself in the refrigerator. Simply dampen paper towels and spread the seeds in a single layer on the paper towels. You can repeat the process as many times as necessary, layering the paper towels on top of one another.

collecting seeds from asclepias plants

Once you’ve finished, place the damp paper towels and seeds in a Ziploc bag and label them with the date harvested and variety. Give this bag to a friend to cold stratify herself or place it in a safe spot in your refrigerator for 30 days and then start in peat pots indoors.

cold stratifying asclepias plants
Place the seeds on a single layer on a damp paper towel to cold stratify in the refrigerator.

Learn more about how to germinate and grow milkweed seed indoors.

Keep A Close Eye On Your Asclepias Plants

It’s really important to keep a close eye on your asclepias patch if you’re trying to prevent it from spreading; once the pods start to harden and you’ve had a frost, get out in the garden and either cut the pods off or tie them up. If you do this every fall, you’ll prevent asclepias from taking over your garden and your friends or family will have plenty of seeds to add to their gardens. The pollinators will thank you, we promise!

storing seeds from asclepias plants
Hand this ready-to-stratify bag to a gardening friend or do it yourself!

Have you had any experience controlling the spread of asclepias in your garden? Please share in the comments below!