NOTE: The specific milkweed species I discuss are for the Northeast, my part of the country. Check the Resources section below to find milkweeds native to other regions.
One of the keys to having monarchs — for their survival now and in the future — is having lots of milkweed. Because of modern changes, such as suburbanization and Roundup-Ready crops, there’s a lot less milkweed than there was in the past.
This is a disaster for monarchs since monarch caterpillars can eat nothing but milkweed.
No milkweed, no monarchs!
We want lots of monarchs, so we plant lots of milkweed for them to lay their eggs on. We’ve tried to maximize our milkweeds in a number of ways — especially since it’s sometimes difficult to find them for sale or at least to find them for sale at an affordable enough price to buy more than just a few.
Purchasing milkweeds
All milkweeds are of the genus Asclepias. When we look for milkweed seeds or plants to purchase, we always look for this name. Sometimes nurseries are afraid to call them milkweeds since people shy away from anything with “weed” in its name, and because milkweeds have an undeservedly bad reputation.
Some nurseries name them something innocuous like “pink butterfly plant,” but that doesn’t help people who are looking for milkweeds. Knowing the botanic name is very useful and helps us find the real milkweeds (if the grower actually uses these more correct names).
And for milkweeds and plants in general, we favor the species, not cultivars or hybrids.
Local ecotype: Now that there is an organized campaign to restore milkweed, local ecotypes of milkweed species are becoming available. If we were to buy any new milkweeds, we would look for plants grown from seeds responsibly collected in our own region. Here in Central NY we’re fortunate that some of our local native plant nurseries are providing local ecotype milkweeds. They also grow them for our HGCNY Wild Ones spring and fall native plant sales. HGCNY’s free Native Plant Shopping Guide shows which nurseries in CNY have native milkweeds for sale.
An aside: We wish more nurseries would offer six-packs of small milkweed plants rather than large, pricey single plants. They grow quickly enough that these large plants aren’t necessary and having one plant isn’t going to really help much.
How will a monarch find one isolated plant? Monarchs usually lay just one egg on a leaf, but they lay eggs on lots of leaves of more than one plant. How could one or two plants be enough food for the caterpillars that develop from the eggs of even just one monarch, who can lay 300-500 eggs? These caterpillars are eating machines! One solution is to grow our own from seed — preferably, locally-collected, local ecotype seed.
The easiest way to have a lot of milkweeds
We bought several swamp milkweed and butterfly weed plants many years ago. They grew well and produced nice pods filled with seeds. Then we started noticing milkweed seedlings! Spotting these volunteers has been the easiest way to have the number of milkweeds we wanted. We’ve mostly seen swamp milkweed (A. incarnata) seedlings, less often butterfly weed seedlings (A. tuberosa).
Unlike some plants, though, these milkweed seedlings aren’t a problem since there never seems to be more than I want. If they do pop up where we don’t want them, we just pull them out, transplant them elsewhere, or pot them up to give away. The more people growing milkweeds the better!
Growing milkweeds from seed
Years ago, when we wanted more milkweeds, we grew swamp milkweeds from seed. (We have plenty of milkweeds now!)
To easily get the seeds without the fluff, we collect the pod when the pod has split, and it has just begun to open rather than waiting for the seeds’ little “parachutes” to start floating all over. We wait until we see the pod start to show the split, though. If you open the pod before it’s ready, the seeds won’t be ripe.
Then, we just hold the end and strip off the seeds. We’re left with the not-yet-fluffy fluff in one hand, and the seeds in the other (or generally in a paper bag).
If we don’t get to them before they’re beginning to get fluffy, we just enjoy the fluff and collect the seeds anyway. It’s just a little more of a challenge to separate the seeds from the fluff.
If we’re not going to be sowing the seeds right away, we store them in a paper envelope or bag, not plastic.
Growing milkweed from seed outside
The easiest way to grow new plants is to do as nature does: sprinkle some seeds around in the fall and wait for spring. The seeds experience winter and know when it’s time to get growing in spring.
To maximize your crop, we wait until after a killing frost. Of course nature plants seeds whenever they ripen and drop from the plant, and plants can grow this way, but the little plants that germinate early could face a killing frost.
We wait to sow the seeds after a killing frost, and the seeds will be ready to grow early in the spring. And seeds often germinate better in cool soil. This is probably the easiest method, but it’s hard to remember to look for them in the spring and to recognize the seedlings as they emerge.
NOTE: I’ve been pretty casual about this since I’m mostly growing some extra plants for my own yard, but local native plant professionals, such as Amanda’s Garden and The Plantsmen Nursery use seed starting mix and cover with ¼” of soil.
A quick and easy method
We wanted more than just the occasional seedling sprouting up at random, though, so we planted seeds ourselves. We sow them in pots in the fall after a killing frost, insert a plant marker, then sink the pots into the ground to wait for spring.
Why the pot? Only because it reminds us that we planted something there, and that’s where we’ll find the seedlings. We’ve generally put a little soil on top of the seeds, but William Cullina in his Wildflowers book says to surface sow. We’ll experiment with both methods and see what happens.
The PLANT LABEL is the important part! In the past, when I started seeds this way but without a plant marker (after all, I OBVIOUSLY would know what I had planted …) come spring I had no idea what was in the pot. Many little seedlings came up the next spring, and even though they were a little crowded, they grew very well.
After procrastinating for a while, I took the next step and pulled the pots out of the ground. So far, so good. But then I just left them sitting there during one of our driest summers.
After about a month, I took pity on them and guiltily knocked them out of the pot, untangled their roots, and planted them. The miracle is that even after this abuse they grew very well.
I’m not recommending this delay “method,” though. Think how much better they would grow if the little seedlings were planted in a timely fashion!
So far — aside from spotting volunteers — this seems to be the easiest way to start milkweeds (and other plants whose seeds I find in my garden).
Growing milkweeds indoors
Why go to the trouble of growing them inside when it’s so easy to start them outside? One reason is timing. As Amanda’s Garden noted, seeds she started on November 11 germinated in late May. When we want to have larger plants for the beginning of the growing season, we start some plants inside. It’s more predictable and lets us control how many plants we produce.
When we grow them inside, cold stratification is really important to get good germination and growth. The purpose is to trick the seeds into thinking they’ve been through winter, which plants native to the Northeast evolved with. And as everyone in Central New York knows, winter means cold and wet. It’s easy to fool the seeds. Just put them in a moist paper towel, then into a plastic bag and leave them in the refrigerator for 3-6 weeks or, as The Plantsmen Nursery recommends, just take them out after 30 days. Check on them occasionally; they may start germinating sooner, and you’ll want to plant them then. And that’s all there is to the simple process with the big name of “cold stratification.”
We experimented to see if cold stratification is necessary.
Here’s the result of our swamp milkweed (Asclepias incarnata) experiment. We planted one flat with un-cold-stratified seeds, and one flat with cold-stratified seeds. Guess which is the flat whose seeds were cold stratified!
In the left flat: We soaked half the seeds, and we simply planted them with no special treatment other than having been stored on the cold porch all winter.
In the right flat: We cold-stratified the seeds (as described above). Virtually every seed came up, and much sooner than the seeds that were simply planted.
For a faster start, we start them indoors 6 weeks before the last frost date, growing them under fluorescent lights. This means that we put the seeds in the refrigerator as early as mid-February, so we can plant the seeds in late March. They start germinating about two weeks after planting.
If it’s too late in spring to cold stratify, we’ve tried soaking the seeds in warm water for 24 hours before planting. In our experience, it wasn’t much better than just planting the seeds, though. And though some recommend that the cold stratified seeds also be soaked in warm water for 24 hours, it didn’t make a difference in our results, although it didn’t hurt them either.
We cover the seeds with about ¼” of soil or less. Cullina says they need light to germinate, so we may try surface-sowing the next time and compare the two methods.
Sometimes we even start some later in the season. These are perennials, so getting off to a slower start the first year isn’t a problem since we’re just getting a head start for the following year. And milkweeds grow pretty quickly anyway.
Multiply by dividing
Although it doesn’t seem to be an officially recommended way to get more milkweed plants, we’ve been successful in dividing swamp milkweed.
CAUTION: This method would NOT work with butterfly weed (A. tuberosa) since it has a long taproot (see photo), and taproots don’t want to be divided.
On the positive side, this long taproot is what makes this species of milkweed more drought-tolerant so it’s good for dry areas or poor soil, just don’t try to divide it — or even transplant it unless it’s just a young seedling.
I haven’t tried dividing common milkweed (A. syriaca), but I’m not sure it would be the best way to propagate them.
Here’s the swamp milkweed plant to be divided. Each stem will become a new plant.
Here’s the root system. You can see that, unlike common milkweed (A. syriaca) that spreads underground, the swamp milkweed’s roots are clump-rooted. They’re pretty self-contained and not inclined to spread.
This is one of the reasons (besides having beautiful flowers) that swamp milkweed (A. incarnata) is a very garden-worthy plant, as compared with common milkweed (A. syriaca), though we grow that, too.
Here I’ve teased apart the stalks, letting their roots untangle as I gently pulled.
Voila! Four plants where there had been one: three large ones and one small one (in the upper right of the photo). Generally in my experience even these small ones grow well.
Common milkweed
These common milkweed seedlings are from our HGCNY Wild Ones plant sale. We’ve distributed thousands of milkweeds as part of the Wild Ones “Wild for Monarchs” project!
I haven’t tried transplanting or propagating common milkweed (A. syriaca), but others have.
Here’s what has been posted on the Monarch DPLEX listserv: “The propagation rhizome of A. syriaca grows about one inch deep. With young common milkweed, I cut a big circle around the plant, then go deep, and take out the whole mass. I pulled up about 3 feet of the rhizome and coiled it up in a flower pot with potting soil resulting in a vigorous lush milkweed bush. I think given the recent discussions I would try to cut it up and see if I could get many pots of milkweed.”
In the fall and spring
In the fall, I leave the dead stalks, perhaps cutting them back a bit if they’re too tall.
Here’s why.
First, milkweeds emerge later than many other plants. The first year I planted them, the following spring I thought they hadn’t survived the winter since most other plants were already growing. But it turns out they just take their time in the spring.
The dead stalks I leave in the fall are a perfect “plant marker” so I know exactly where to expect them to emerge in the spring.
Second, some birds find their fibers useful as a nest building material. People clean up way too many bits of nature that birds and other creatures need for raising their young.
Third, these hollow stems are a good place for birds to find a tasty insect overwintering or to cache some seeds or insects of their own.
Notice the small holes in the stalk where insects have exited (or have been pecked out).
Resources
- Monarch Joint Venture:
- This partnership (of which Wild Ones is a member) has a number of excellent factsheets (some in Spanish) available on their fact sheet web page including:
- Milkweed information sheet
- Gardening for monarchs
- Potential risks of growing exotic milkweeds for monarchs
- LOTS MORE! Be sure to check the menu on the left on the MJV page
- Monarch Watch:
- Growing milkweeds
- Milkweed Market – To purchase milkweed plugs suitable for your own ecoregion
- The Xerces Society:
- Milkweed Seed Finder
- Project Milkweed includes more info on finding milkweeds – specific to each state
- Milkweeds: A Conservation Practitioner’s Guide – Comprehensive; maybe too much for the backyard gardener, but there are good sections on milkweed pests and diseases
- ADKAction:
- Monarch Butterfly Conservation – Preserving Monarch habitat in the Adirondacks.
- Mona Miller:
- Wild for Monarchs:
- Butterfly Encounters:
- VIDEO: Cold moist stratification – a more structured method than ours
Meadows for monarchs
- Gary Stell:
- Being in the city, we don’t have a meadow to mow, but if you do, here’s some advice from Gary Stell, a milkweed expert from Central NY, on mowing meadows for wildlife, especially monarchs:
- A meadow should be mowed at least once every three years to eliminate trees and other woody plants.
- Mow 1/3 of the field each year—never the whole field at once—leaving it 6 inches high.
- Mowing 1/3 of the field in fall after the monarch migration has completed, leaving 2/3 of the meadow unmowed, will leave the majority of the seed for birds and other wildlife.
- Don’t mow swamp milkweed or butterfly weed. Swamp milkweed blooms in mid- to late-July and is an important source of nectar for butterflies and bees. Butterfly weed blooms in early July. I have no experience with mowing it but doing so may kill the stand. Monarchs generally do not select butterfly weed for oviposition; it’s a better nectar source than host plant.
- Common milkweed (Asclepias syriaca) responds well to mowing. My best experience mowing common milkweed was with a dairy farmer who harvested first cutting from a hay field (over 100 acres) where milkweed was very common. First cutting was lush and ready early in June. Milkweed typically emerges from the ground the first week in May. In many years the monarchs are only just arriving in early June so the larva and pupa death from the mowing are minimal if at all. The pleasant surprise was the milkweed fully recovered and bloomed late July instead of July 1 and produced a full crop of seed although matured a week or two later than other wild milkweed.
Reflections
I love Bill Cullina’s description of milkweed. I always think of it whenever I’m getting milkweed seeds out of their pods. Cullina’s books are always a delight to read!
Dry milkweed down has a buoyancy that would make helium jealous, so if you let the pods dry and split, I recommend you clean them outdoors.
~ William Cullina, Wildflowers: A Guide to Growing and Propagating Native Flowers of North America