Why You Need Milkweed: A Guide to Growing Asclepias

Asclepias spp.

Meadows are one of my favorite places to be, largely because of the lovely milkweed that I often find there.

Tall and topped with sprays of flowers, an arrow-straight stem with funky looking oval leaves, and crawling with caterpillars, beetles, and butterflies? Yeah, that’s the plant for me.

You’re probably familiar with the common milkweed seen in meadows and roadsides across the country, but the milkweed family is actually huge. We’re going to take a look at some different cultivars used in gardens, and learn how to grow this plant.

An orange and black Monarch butterfly is perched on a cluster of pink milkweed flowers, with green leaves, printed with green and white text.

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More important than that, though, we’re going to talk about the importance of milkweed in the environment. Here’s what’s ahead in this article

Buckle in, we’re going to get started.

Start with the Basics

Milkweed is botanically known as Asclepias spp. and has over one hundred known species. It was named by Carl Linnaeus after the Greek god of healing, Asclepius, and the species is native to the Americas.

Closeup of a cluster of purple and white Asclepias flowers, with green leaves, in bright sunshine.

This nod to a god of healing is because of the use of the sap as a medicinal aid, namely for dysentery and warts, by the native people in the Americas.

While the milky white latex inside the stems is often toxic, the rest of the fibers in the plant have earned Asclepias the nickname “Silk of America.” These fibers have been used for insulation and cleaning oil spills, and can be found in some hypoallergenic pillows.

Orange asclepias blooming in a garden bed, with blue flowers in the background.

But most of us know the value of milkweed because of its necessity in the life cycle of the monarch butterfly.

The Milkweed and the Butterfly

As a kid, I remember learning that milkweed sap is toxic. But monarch caterpillars can eat Asclepias safely and then become toxic to predators later on in their life cycle.

Our teacher went into the meadow outside of the school, found a monarch caterpillar on a piece of milkweed, and brought it in to show us.

Yellow, black, and white striped Monarch butterfly caterpillar, in the palm of a person's dirt-covered hand.
Photo by Matt Suwak.

Hoards of children watched the chrysalis formation and waited impatiently for the butterfly to molt. It did, eventually… over the weekend, when nobody was around!

Our teacher said she released it into the wild to prevent it from being cooped up for too long.

Closeup of a light green Monarch butterfly chrysalis, with a yellow and black stripe at the top, in the palm of a person's dirt-covered hand.
Photo by Matt Suwak.

I don’t know if the thing simply died and she didn’t want to break our tiny 7-year-old hearts, but I do know that the lessons she taught about the natural dynamic of milkweed and butterfly stuck with me for the rest of my life.

How Integral Is this Relationship?

In a word: it’s absolutely integral!

Monarch caterpillars utterly depend on Asclepias for their diet, but so too do a number of insects all specialized in dining on the otherwise-toxic milky sap of the plant.

A green stalk of milkweed with narrow green leaves and a monarch butterfly caterpillar feeding on the plant, with a meadow, trees, and blue sky in the background.

A monarch butterfly will lay its eggs on the underside of a leaf. In fact, this is the only place where a monarch will lay its eggs.

When the eggs hatch, the tiny caterpillars start going to town, and chomp down on the Asclepias.

Bright red Asclepias flowers with yellow centers, on a plant with green stems and long, narrow, green leaves.

Amazingly, the plants have built-in defenses like irritating hairs and their aforementioned natural toxins to slow the buffet line down, but they do not altogether prevent the insects from using the plant as a food source.

A bee pollinates white and rose-colored milkweed flowers growing in a cluster on a plant with green buds and leaves.

Most monarchs live for an average of 4 weeks, but every fourth generation lives for 6 to 8 months! This is the generation that will complete an incredible flight to the southern regions of North America, to roost and overwinter before continuing the journey northward to start the cycle anew.

This plant is also a primary food source and shelter for a variety of beetles, and has earned its place as a vital native plant species for healthy ecosystems nationwide.

The Butterfly Garden

The popularity of butterfly gardens was spurred in a big way because of the plight of the monarch, and this style of garden has attracted plenty of folks to the realm of gardening. That makes me love butterfly gardens!

Asclepias and other native flowers like black-eyed Susans, echinacea, joe-pye weed, sweet alyssum, and sunflowers are some of the easy-to-grow plants that may make up a successful butterfly garden.

An orange and black Monarch butterfly on a milkweed plant, with green leaves and fuzzy light green seed pods, with yellow black eyed-susans in the background.

All butterflies are pollinators and are attracted to this style of flower. Plant the right types, and you’ll have a never-ending summer show of cascading butterflies!

The biggest benefit of a healthy butterfly garden is that it strengthens the rest of your local ecosystem. When butterflies are present, that means birds, bats, and other critters that feed on butterflies are able to make a resurgence as well.

Upward-facing shot of orange milkweed flowers with green leaves and long stems, growing in front of a metal fence, with a brown wood fence and a tan stucco building in the background.
Photo by Matt Suwak.

Think of a butterfly garden, and milkweed’s place in it, as an essential strand in the food web!

Ideal Planting Conditions and Potential Problems

Despite sharing a name, many milkweed types require different growing conditions. Some prefer hot and dry areas while others thrive only in moist conditions, but they all need ample sunlight to do their best.

The common milkweed does well in what might be considered average conditions: moderately dry and well-draining soil, no special fertilizers or nutrition requirements, and about 8 hours of sun a day.

Bright orange asclepias flowers growing on tall stems with narrow green leaves in a field, with blue sky and fluffy clouds in the background.

Most of the species I’ve worked with prefer that “average” blend of characteristics. These plants can be plopped into the garden and be given a springtime coating of compost, then be on their way to growing lovely and stunning flowers.

Most don’t require any extra watering except during the hottest dry spells.

Pink and white Asclepias with narrow green leaves, on a brown background with selective focus.

Because of their toxicity, Asclepias also attracts few ailments or problems.

Besides typical fungal issues that can be found in many areas of the garden with an abundance of moisture, milkweed can suffer from general heat stress and damage. Remove yellowed leaves and those with lots of damage from insects.

Red and yellow Asclepias flowers with narrow green leaves.

Mites can become a problem, but any general insecticidal treatment works; just be careful not to poison those desirable insects, as well!

Milkweed yellows phytoplasma is a more serious issue identified by malformed, yellowish growth and branch dieback. The only solution here is to remove and destroy the infected plants before they spread the ailment to other plants.

To avoid these conditions, keep your plants thinned out and avoid standing pools of water and over-watering in general. Milkweed would rather be too dry than too wet!

How to Start Growing Your Own (and Where to Buy Them)

Many garden centers will sell a variety of milkweed species during the growing season, but finding live plants online can be difficult. That’s because, for all of their toughness to natural predators and tolerance of growing conditions, Asclepias can be very sensitive to transplanting and handling.

For that reason, I recommend starting yours from seed. Fortunately for those who really like to do it all yourself, milkweed plants produce extraordinarily generous bounties of seeds for you to harvest.

Milkweed seeds on a dry pod that has broken open in the fall, with dry, dead stalks of the plant surrounding it, and green trees in the distance.

Each individual seed pod can contain a hundred or more seeds, and plants have multiple seed pods each!

I usually collect my seeds from the gardens of friends and clients, but I’ve snagged a single pod or two when out hiking as well.

Asclepias seeds need a period of cold to become viable, with some added moisture. This process is called “cold stratification,” and you’ve got two easy options for how to accomplish this task:

1. Chill Manually

Place your seeds on a damp paper towel and plop them into a ziplock bag.

Label the bag with the date, and keep it somewhere in your refrigerator where it won’t be bothered; you need to leave the seeds largely undisturbed for about thirty days before they become viable.

After stratifying, you can start your seeds in a growing medium about three to four weeks before the last freeze date.

2. Direct Sow in Cool Climates

Directly sow your seeds in the garden in the late fall, and let the winter weather take care of cold stratification for you!

A hand holds a milkweed pod, with feathery white seeds.

If you’re cold stratifying the seeds yourself…

  • Start the seeds, preferably in peat pods.
  • After wetting and preparing the growing medium, add one to three seeds per pod. If you use more than one seed you’ll have better luck that at least one will grow, but you’ll need to thin out the weaker seedlings.
  • Layer about 1/4” of soil onto the seeds and keep them in a warm area with lots of light.
  • Be very careful when moving and planting your Asclepias seedlings; they are very fragile and need delicate care.
  • Plant the pods directly into the garden before the plants reach about 3” in height to avoid damaging the sensitive taproot, and wait until after the last freeze date before planting.
  • Ensure the top of the peat pods is covered in soil, or carefully cut any extra pieces away to prevent the peat from stealing moisture from the seedling.

All of these steps can be skipped if you’re sowing the seeds outdoors, but I would recommend planting lots of extra seeds if you take this route. You can thin them out later as the season goes on, and this helps to avoid the frustrating experience of having none of the seeds germinate because you sowed too sparsely.

100 A. Syriaca Open Pollinated Seeds, available via Amazon

If you want to plant the common milkweed (A. syriaca), this is a good bunch of seeds! Common milkweed grows in zones 4-9, and reaches a height of about three feet. It’s the plant we’re most familiar with seeing growing in the wild.

100 A. Incarnata Open Pollinated Seeds, available on Amazon

For the swamp milkweed (A. incarnata), these seeds receive consistently good reviews, and are sold via Seed Needs USA. The swamp variety of Asclepias will grow in zones 3-9 and can reach a height of five feet tall!

50 Whorled Milkweed Seeds from Zellajake Farm, available via Amazon

The whorled milkweed (A. verticillata) is a lovely plant for those who want something a bit more shy (reaching about two feet tall max) that grows in zones 4-9. These seeds are from a reliable grower and have good germination rates.

Red and yellow Asclepias curassavica with an orange and black Monarch butterfly, on a plant with narrow green leaves, on a mottled green and brown background in soft focus.

Heirloom Bloodflower Seeds, available from Eden Brothers

Want to add a splash of dazzling color to your flower beds? The bloodflower, or sunset flower (A. curassavica) is another stunning variety, with red and yellow flowers and a max height of about 36 inches. This variety is recommended for zones 3-9.

A cluster of orange Asclepias tuberosa flowers, with an orange and brown butterfly perched on top, with green foliage in shallow focus in the background.

A. Tuberosa Seeds, available from Eden Brothers

The aptly named butterfly weed (A. tuberosa) is another colorful variety, with vibrant orange flowers. It will grow to a height of 24-36 inches in zones 3-9.

Most of these companies recommend cold stratifying the seeds before spring planting to further guarantee germination, so order early! Otherwise, they’re ready to go if you sow outdoor in the fall.

White blooming Asclepias 'Ice Ballet' with green narrow leaves.

A. Incarnata Ice Ballet Plant in #2 Container, available from Nature Hills

If you REALLY want a live plant, I recommend ‘Ice Ballet.’ It grows to reach about two to three feet in height and has a lovely shade of white to its flowers. I’ve seen it in a few select gardens, and I wish I saw it in more because this plant is a real beauty.

Get Planting and Attract Those Butterflies!

While they are sensitive and require special handling when young, Asclepias become hardy and easy to care for within a few weeks. Better yet, they attract a veritable swarm of wildlife, and that’s always a good thing for the eco-conscious gardener!

Pink Asclepias flowers with green foliage.
Photo by Matt Suwak.

Asclepias are at their best when they’re given room to grow and do what they want to do, but with the right attention, they can shine in even the most well-manicured garden. The beetles, the butterflies, and the pollinators will all thank you for giving this iconic American perennial a shot in your garden!

Do you have some extra tips on growing milkweed to share, or maybe a few questions? Please drop us a line in the comments below. Thanks for reading, and check back soon!

Photos by Matt Suwak © Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Product photos via Nature Hills, Zellajake Farm and Garden, Seed Needs, and Eden Brothers.

About Matt Suwak

Matt Suwak was reared by the bear and the bobcat and the coyote of rural Pennsylvania. This upbringing keeps him permanently affixed to the outdoors where most of his personal time is invested in gardening, bird watching, and hiking. He presently resides in Philadelphia and works under the sun as a landscaper and gardener, and by moonlight as a writer. An incessant questioning of “Why?” affords him countless opportunities to ponder the (in)significance of the great and the small. He considers folksy adages priceless treasures and is fueled almost entirely by beer and hot sauce.

32 thoughts on “Why You Need Milkweed: A Guide to Growing Asclepias”

    • That’s an excellent article, thank you for sharing. I’m very curious about the effects of these domestically-bred monarchs breeding with others born in the wild and potentially passing down that seeming inability to migrate.

  1. Matt, they’re out of control! That peak is 12′. The eave is 8′. Then the rain knocks them down, breaking some of the stems. How do I keep them pruned—that is, how hard and how late can I prune them w/o losing the flower heads?

    • Wow, look at them grow! That looks like a Joe Pye weed (it’s not really a weed!) to me, maybe I haven’t had enough coffee yet.

      For controlling perennials and fast growers like this, you can tip them back in the late spring. The magic number is usually 1/3rd of the height of the plant, so if your milkweed is six feet tall in May you can bump them down to a good four feet. You could tip them back again a few weeks later, but never do that pruning when you see flowers forming.

      You might find some flower heads getting crispy and unattractive while other flowers are forming at a lower height. I’d remove the unattractive and fading flowers thereby reducing the overall height of the plant, and allowing the shorter flowers to take over.

      By controlling the height this way early in the growing process you can limit their maximum mature height. Some plants are more forgiving of this process than others, but it’s a pretty safe process. For now, though, you can’t cut them back without losing those flowers. Staking could be a solution; get a few ten foot stakes and drive them into the ground behind the plant, and tie the plant loosely to the stake in two or three areas.

      Otherwise, enjoy the flowers now and try not to think about them crashing down from that heavy rain!

    • From my experience with Eupatorium purpureum (Joe Pye weed) they grow up to 8′ and flower in late fall here in zone 8 so perfect for providing a late-season source of food when the rest of the garden isn’t flowering much. Definitely need staking, but definitely worth keeping if you can!

  2. Hi, I have healthy milkweed plants that overwintered and came up in the spring. They are about 3’ tall but have no signs of flower buds at all and although we have millions of various butterflies all over our yard and multiple flowers, butterflies do not get on the milkweed plants. I think they were swamp milkweed. When do they usually bloom? Thanks

    • The milkweed around here in Philly didn’t start blooming until mid July or so, they can certainly be a late or stubborn bloomer in some areas.

  3. I live on Long Island in NY. I planted two milkweed plants fairly close to each other and near other butterfly-loving plants. (as a trial I only did two but I intend to plant a whole area of my garden with them). They’re growing great and are about 2ft tall BUT the stems are basically leaning so much they’re growing into other plants.

    Are the main stems not strong enough to stand upright? Did I not plant enough together to provide natural support? Anything I’m missing here? The leaves look healthy and they feel sturdy when I pick the stems up. They get plenty of sun. I’m at a loss, maybe they grow this way?

    Thanks for the help!

    • Doesn’t seem like you’re doing anything wrong! Many plants get top heavy like this; ornamental alium, dahlia, and marigolds come to mind first. The trick is to stake them up using a sturdy piece of wood or bamboo driven into the ground. Use some string to loosely tie the plant stems to the stake, and voila, problem solved!

  4. Hi I just started with feeding Caterpillars…found some cats on my common milkweed plant and butterfly milkweed..well for the first time I have a cat that went to the top of my screen enclosure and this morning I found it in the J position..I have 4 more that are getting ready to leave the leaves..my husband and I are starting a butterfly garden for next Spring, so your info on Milkweed plants was very useful and informative..thank you

    • Great, I’m glad it was a good and helpful read! Seeing bits of nature enjoying our hard work is immensely gratifying.

  5. Once the caterpillar strip the leaves and leave a bare stem, should it be pruned back? I have a very large bunch of hungry caterpillars.

    • I tend to leave plants in place, leaves or not, until it’s clear the stem is not producing any more leaves and is dying back. You can tell this is happening when the stems turn yellow, then brown, and start to grow crispy. If before this stage the stems begin to develop signs of disease, you can cut them right to the ground and wait for their return next year.

  6. Great article! I planted a swamp milkweed last spring and it grew beautifully this summer. I was honestly surprised by how many monarch caterpillars hatched and grew on the bush. Questions…should I cut back the stems of the plant over winter or wait and cut back in the spring and how far back should I cut them?

    • That depends! If you have room to keep the stems up you can leave them for winter interest, but you’re free to cut them back if you don’t like the way they look. It’s really a question of preference.

      As to how far you cut them back, I like to leave a few inches visible as reference to where the plant is. It’s really easy to forget what’s where in the garden, especially in the springtime when everything kind of looks the same. You can leave a small marker, maybe a bamboo stake, to indicate where the plants are so you don’t accidentally weed them. Or you can use the fancier copper nameplates, your call!

  7. David, REALLY great and enjoyable write up!! I have some CA beers in my fridge so stop by when you come to the West Coast and we will enjoy a couple!

    • Hey Becky, love that region of Pennsylvania. To answer your question, most milkweed could be considered invasive, if only because they produce prolific amounts of seeds and are eager to set up shop just about anywhere. Fortunately controlling that undesired spread is relatively easy, since the seed pods are so huge and easily identified. Simply snip the pods away from the plant after they’re formed and dispose of them if you don’t want the plant to spread.

      I’ve seen people set up rather large “blobs” of milkweed, huge masses of the plant that are allowed to freely seed within their confined area. These chunks of plants are kept in line by aggressively weeding out anything else growing on the plants border, and by removing any volunteer milkweed in undesired areas before the plants can go to seed.

      So in my experience we’ve got two options, the first is to pick a few plants and remove their seed pods before they open up, or set up an area where milkweed can go wild and remove anything that remotely resembles it outside of desired areas.

      Let me know if you have other questions!

  8. Hello Matt. This is a great article. Thanks for taking the time to post it! Can you recommend a variety of milkweed that starts to germinate in early spring. I’m in zone 5b (southern Ontario) and grow swamp milkweed but it usually doesn’t start to come up until mid/late spring and usually isn’t a decent size until at least early summer. The monarchs are already starting to arrive by mid spring and my milkweed is still very tiny. I’m hoping to find a variety that will be well underway by the time the monarchs arrive.

    Thanks again.

    • I’d say you have three options for early-ish blooming. It can be difficult to get these to bloom early if the weather isn’t on their side! The first option is the native common milkweed we all know. It’s going to be tough to find this in garden centers but you can easily collect seeds, cold stratify them, and get them started for next year.

      Another option is butterfly milkweed or whorled milkweed. They both tend to bloom earlier in the season, especially the butterfly milkweed. It has nice orange flowers too, so that’s another bonus.

      I hope these work for you. If you have other questions we’re always here!

      • Thank you for the speedy reply Matt! The info you provided is great and gives me a few options to try out. I like to have variety in my garden so these will give me some exciting new choices to experiment with.

        Thanks again!!

  9. Hi, I ordered six plants online and planted them here in MI around Memorial Day. They were about 3 inches high. They have only grown about 3 more inches and are sprawling along the ground. Am I doing something wrong? I think from your article I have been watering them too much, but we’ve had a month of 90-degree days and very little rain here. They are nice and green and growing, just really slowly. I had expected some flowers this summer.

  10. Hi Matt, thank you for the very interesting info. My question is how to know what is happening to my standard milkweed here in CA. I’ve planted 4 of them along a berm between my neighbor and us. They are interspersed between blue sage and are on a once a week drip system. They seem to flourish for a few months and then start dying back and have some sappy kind of film and all the leaves and flowers are gone. The soil is not very wet. I can’t figure out what happened

  11. I’ve got some asclepias to plant. I was excited but now I’m worried. Someone told me I would get lots of aphids. I have rose bushes so aphids concern me. Help, I don’t know what to do.

    • Hi Suzanne! Ugh, aphids. I understand your concerns completely — I had a bad outbreak in my delphiniums this year, weirdly.

      The most common aphid to affect milkweed is the orangish-yellow oleander aphid. Thankfully it’s easy to spot and tell apart from tiny, pale white monarch butterfly eggs.

      Vigilance is the best way to keep the aphids away, so check your milkweed every day. If you notice even a few aphids on the milkweed, spray them off with a hose (check for monarch caterpillars or eggs first!). Or, spray the aphids with isopropyl alcohol, which won’t harm monarchs unless they’re directly sprayed with it. Avoid directly spraying any caterpillars or eggs. Remove aphid carcasses with your hands or with the hose.

      This will keep them from invading your roses! It might also comfort you to know that oleander aphids much prefer milkweed over roses, so they may not even try to infest your rosebushes, although it’s definitely possible.

  12. I am going to mass plant common milkweed in a large plot on our farm. Though I am an experienced pollinator gardener, grow milkweed and raise Monarchs in a habitat, this bush hogged field has me stumped. I would love to hear from anyone who has started with a grassy area and has successfully mass planted with seed. Help?
    FYI I live in zone 7 in NC.

    • Hi Ann,

      Milkweed spreads pretty easily from seed so I anticipate that direct seeding in the field will yield good results. Over time, the plant should continue to self seed and spread further by its network of creeping rhizomes.

      Since milkweed requires a period of cold stratification, it is best to either seed in late fall after a frost but before a hard freeze or to cold stratify in the refrigerator an seed in the spring as soon as the soil can be worked. To do this, wrap seeds in a damp paper towel or damp sand and place inside a ziplock back. Store in the refrigerator for at least 6 weeks.

      Please also see my response in milkweed winter care for more on creating a lasagna bed.

      Thanks and good luck!


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