Note that if you purchase something via one of our links, including Amazon, we may earn a small commission.
Dear Dot,
In the last couple of years I've planted about 300 Milkweed seeds, not one of them grew. I've let some freeze in the ground and I've frozen some in the freezer. I've been told that some take two years to germinate, none of mine did.
– Tom, Toronto, Ontario
The Short Answer: Let’s summarize the steps to maximize the likelihood of thriving milkweed, Tom, noting that most experts believe that Common Milkweed is the easiest species to start with, though Swamp Milkweed may be the most reliable of the Ontario-native varieties:
- Collect pods just as they begin to crack open. At this stage, seeds separate easily from the silk.
- Place seeds in a brown paper bag for eight weeks in a dry, shaded spot to finish ripening.
- Transfer seeds to a small envelope (label with the species name) and store in a refrigerator — not a freezer — for three months.
- Sow seeds in flats using a garden seed starter mix, water them, and place on a sunny windowsill. Germination should occur within about two weeks.
Dear Tom,
Dot’s milkweed-loving heart hurts simply reading your letter. And I hesitate to share the following, lest you think I’m gloating. I assure you I’m not. Rather, I’m hoping that my success will inspire you to keep trying. And I vow to you that I will do my best to unearth expertise to help you, too, achieve milkweed success.
Roughly a decade ago, Dot responded to an offer by the David Suzuki Foundation to receive and plant milkweed seeds. The environmental organization asked only that I provide my location so they could ensure I received the appropriate native milkweed species and, shortly thereafter, my seeds arrived in the mail, at which point I poked them into the soil in the garden outside my office windows.
Even now, with about a foot of snow on the ground, I can see their thick bamboo-like stalks, winter soldiers awaiting spring.
Once the warm weather hits, my milkweed will grow like, well, like a weed. New milkweed plants will no doubt also poke up in both my garden and (because they spread) my lawn.
I even took some seeds from a milkweed pod in my garden to my father’s home on Lake Huron, and milkweed now flourishes there along his dirt road. Did I do anything special to make my milkweed so prolific? I did not. And so I am bewildered at the challenges you have faced coaxing milkweed from your soil.
Consequently, Tom, I reached out to a number of experts to see if they might know why your milkweed is so stubborn … and how you might turn things around.
But first, let us share with readers why you and I are so enamored of milkweed:
🐛 Milkweed is the essential host plant for the caterpillars of Monarch butterflies. Monarchs can feed on other plants, but without milkweed, they won’t lay eggs.
🦋 Species that feed on milkweed absorb its toxins, which are harmless to them but make them less appetizing to predators.
🐝 Milkweed is rich in nectar and pollen and supports a wide variety of species, including bumblebees, moths, butterflies, and even hummingbirds.
🕊️ It even provides nesting material — birds will use both fiber from the stems and, when the pods burst open, the white fluff (silks).
But … milkweed is under threat. According to the National Wildlife Federation, Monarch butterfly populations are down 90% since the 1980s, thanks largely to habitat loss from housing development and agriculture.
And yet, when Dot reached out to many experts, responses were, shall we say, less than helpfully enthusiastic. If I might sum them up, they amounted to, “How the heck should I know why his seeds aren’t sprouting?” Most simply directed me to various websites, which … have these people met the Internet? Nobody agrees on anything! Sandy from the Ottawa Field Naturalists’ Club (OFNC) did reply, offering you vindication by noting that “we find Common Milkweed hard to grow. Even in pots under controlled conditions, the seedlings are tiny and very slow to grow. Swamp Milkweed and Butterfly Milkweed are much easier, although Butterfly Milkweed often dies after growing beautifully for several years. So Swamp is the easiest and most reliable.” Sandy then directed us to OFNC’s “Easy steps for growing milkweed from seed.”
I, however, wanted to address your specific issues Tom, so I’m grateful that you further clarified them to me, writing, “I separated the silk from the seeds and planted them in a scrape in the grass, not very deep. I also planted some in a bit of bare ground.” Furthermore, you told me that you “had some pods from last year which I put out to freeze a few weeks ago. Unfortunately either the wind or an animal took the tub; I found it empty in the backyard. I had intended to take the seeds out of the pod, put them in the watering can and broadcast them using the water. I’ll look for pods when the snow melts, [but] if I don't find them, I’ll have to wait ‘til next fall.” To add to your ordeal, you told Dot that, “I got wrong information about scarifying the seeds. I was told that planting them before the first frost would trigger the germination process. Also that the process could be accelerated by putting them in the freezer. I did that with some of them.” Yet despite all your efforts, Tom, you remain sadly bereft of milkweed.
But good news — and milkweed! — is on the horizon, though it might be a slightly distant one. When Dot reached out to Tim Boland, executive director at Polly Hill Arboretum on Martha’s Vineyard, we found in each other a kindred milkweed-loving spirit. Tim suspects your problem arises from either storing or harvesting, as that’s where problems typically arise. He’s operating on the assumption that you’re attempting to plant one or more of the three most common species — orange milkweed, swamp milkweed, or common milkweed.
“We propagate our milkweed species by first harvesting when the pods initially start to crack,” Tim tells me (to tell you), although, of course, this assumes that one has existing milkweed plants and existing milkweed pods on the stalks. But stay with us, Tom, because let us imagine the day when that is true for you. “At that stage, while the seeds are in a soft row, they easily come clean from the silk.” Tim explains that “the silk’s primary function is to catch the wind and disperse the seed, like a parachute.” Neither the pod nor the silk helps with germination.
Once you dislodge the seeds from the pod and the silk, keep them in a brown lunch bag for eight weeks somewhere dry but out of the sun, where, Tim explains, they will continue “ripening.” From there, he advises us to place the seeds in a small envelope (recording the plant name in case you have more than one type) and store them in a refrigerator — not a freezer — for three months. (This is where, Tom, a time machine to send us back to the fall might be helpful.) In mid-March, which is when I’m writing this to you, Tom, the folks at Polly Hill sow their seeds in flats of Fort Vee Vermont compost (but you can use any garden seed starter, Tim says), water them, and place them on a sunny windowsill. Germination occurs within two weeks.
Tim suspects that your problem might be that you’re sowing seeds directly into the ground, which, he says, can have complications. “The seeds are often eaten, and they’re prone to fungal infections,” he explains, noting that Polly Hill cultivates seeds under sterile conditions. Even once established, he says, “deer will eat them, despite people saying they won’t.”
Despite the ONFC’s differing opinion, most people think that common milkweed is the easiest species to grow so, if possible, you might want to start with it. Other species native to Ontario include: Poke Milkweed (Asclepias exaltata); Swamp Milkweed (Asclepias incarnata); Purple Milkweed (Asclepias purpurascens); Butterfly Milkweed (Asclepias tuberosa); and Whorled Milkweed (Asclepias verticillata).
While, unfortunately, the helpful Tim Boland’s timeline doesn’t favor milkweed in your garden this spring, Tom, perhaps you splurge on some commercial seedings and then harvest those plants’ pods for future seed harvesting and sowing.
Dot very much hopes that these instructions help not just you, Tom, but any milkweed-friendly folks, in propagating these plants that are so critical to the lovely orange and black Monarch butterflies, who will be arriving mid-May to June in your area and looking for a place to lay their eggs. (See my summarized instructions above in the Short Answer for an easy, step-by-step guide.) Let us hope the Monarchs find a milkweed home in your garden, Tom. On behalf of them and Dot, thank-you for your persistence.
Zealously,
Dot
