How To Grow Asclepias - Milkweed & Butterfly Weed

By David Salman, High Country Gardens Chief Horticulturist

Asclepias, commonly known as Milkweed or Butterfly Weed, are sun-loving plants that are essential perennials for monarch butterflies providing food for caterpillars and nectar for adult butterflies. Each caterpillar will eat 20 or more milkweed leaves before maturing into a Butterfly. Learn more about Monarchs and Milkweed in our article: Saving The Monarch Butterfly.

The more Milkweed you plant, the better! In addition to attracting butterflies, it will also attract other pollinators, such as beneficial native bees. Milkweed transplants readily as actively growing or dormant plants. You can also start milkweed from seed with a few simple tips. Read on for tips for growing Milkweed.

When To Plant Milkweed
Where To Grow Milkweed
Growing Tips
Growing Milkweed From Seed
Additional Resources

Watch: How To Grow Milkweed With David Salman

When To Plant Milkweed

Most Asclepias species are late to wake up in the spring, and will often be shipped as dormant plants. These perennial species stay dormant later in the spring than many other plants, especially when they are grown in pots. Don't despair if your milkweed is asleep. The white roots and woody crown are alive just waiting for consistently warm weather to wake up and begin to grow. It's fine to plant dormant plants; don't up-pot them for planting later in the growing season.

Tips for planting dormant perennials:

Don't up-pot them to hold for later planting.
Prepare the soil, plant them, mulch, water thoroughly after planting, and wait.
Once the weather warms and the plants begin to grow, water thoroughly but infrequently (once every week to 10 days)

Cold hardy Asclepias are great perennials to plant in the fall. Come spring, they are established and ready to host caterpillars on their leaves and feed adult butterflies with their flowers. If you follow the planting tips below, Milkweed can also be successfully planted in spring.

Carefully remove the Milkweed plant from its pot by loosening the pot from the rootball. Place your hand around the plant and turning it upside-down to slide the pot off the rootball. Don't tug at the stem, as you could damage it.
Before planting, make sure to score the roots with your hands or a pocketknife, so they will spread out into the surrounding soil from the rootball.
Water after planting and about three times a week until the plant gets established.

asclepias roots — Dormant Asclepias with no foliage but healthy roots

Where To Grow Milkweed: Soil and Light

Asclepias is a widespread genus native to landscapes throughout North America. Generally, these species grow in a wide range of soil types.

Asclepias need at least 6-8 hours of full sun to do their best.

Swamp Milkweed (Asclepias incarnata) prefers more moisture and will do better in wet to moderately moist soil conditions. They do well in areas with higher rainfall, such as the eastern U.S.
Butterfly Weed (Asclepias tuberosa) does better in dryer areas, such as the western U.S. It needs sandy or gravelly soils. The exception is the Clay form does well in heavier soils, including dry clay. Plant in full hot sun.
California Narrow Leaf Milkweed (Asclepias fascicularis) is a western native species of Asclepias, easy to grow in a wide range of soils and recommended for use in the West.

Mulching Milkweed

Most Milkweed does not need mulching, except in the hottest climates.
In dry areas, Butterfly Weed prefers a gravel mulch.

Watering Milkweed

When planting dormant plants, water thoroughly after planting and wait to water again until the plant comes into active growth, at which time a deep watering every week or so is adequate. Take care not to overwater young transplants.
After their second growing season, Milkweed only requires deep but infrequent watering.

Fertilizing Milkweed

Use ourRoot Stimulator Combo Pack (liquid seaweed and SuperThrive) when you water during the first few months in the ground.
Avoid fertilizing new transplants, especially with water-soluble chemical fertilizers. Good soil preparation and root stimulator is all they need for their first year.
In gardens, fertilize Asclepias just once in fall with Yum Yum Mix.
Naturalized plantings don't need additional fertilization.

General Growing Tips

Often Milkweeds won't grow much their first season in the ground, so be patient. They are establishing their root system and crown. By the second growing season, the plants will begin to get bigger and look more robust.
The bitter milky sap makes these plants highly resistant to deer and rabbits.
Asclepias have a long, carrot-like tap root that should remain undisturbed after planting and should NOT ever be divided.
All species of Asclepias are late to emerge in the spring, so don't be concerned if other perennials come up first and they remain dormant.
Asclepias syriaca and A. speciosa will spread to make big patches of plants and are best planted in parts of the landscape where they won't crowd out less vigorous plants. Not recommended for the prime spots in your perennial beds.
Asclepias incarnata (Swamp Milkweed) is a more refined grower and is fine to include in perennial beds.
Oftentimes, Milkweeds won't grow much their first season in the ground, so be patient. They are establishing their root system and crown. By the second growing season, the plants will begin to get bigger and look more robust.
To encourage re-seeding and provide winter interest with their ornamental seed pods, leave the stems intact over the winter. In mid-spring, remove old stems just above ground level.

Choosing The Right Milkweed For Your Garden

To learn more about Milkweed varieties, and the relationship between Milkweed and Monarch Butterflies, see our article: Saving The Monarch Butterfly By Planting Milkweed

Growing Milkweed From Seed

Neil Diboll, founder of Prairie Nursery in Wisconsin, and a pioneer of prairie restoration says this about seeding Asclepias: "Seeds of all the members of the genus Asclepias that I have worked with benefit from a 30-day Moist Stratification period to break seed dormancy. The seeds germinate best under warm soil conditions. They can be successfully seeded in fall as a “dormant seeding” to improve germination in spring. Fall planting after frost will provide necessary cold stratification.

All species (A. tuberosa, A. syriaca, A. sullivantii, A. incarnata) will also germinate moderately well when seeded into warm ground in mid to late spring with only Dry Stratification treatment."

Seed Stratification

Seeds can be moist-stratified by mixing seed with moist (not soggy) sand in a zip-lock plastic bag and placed in the refrigerator for 30 days. After 30 days of cold moist storage, the seed's natural chemical germination inhibitors have dissipated and are ready to sprout.

Asclepias Tuberosa and Lavandula angustifolia 'Sharon Roberts'

Helpful Tips For Growing Orange Butterfly Weed (Asclepias tuberosa)

Orange Butterfly Weed has a deep-growing taproot, and it is much more finicky about the soil in which it prefers to grow. The most commonly available Butterfly Weed seed of this species is grown from populations originating east of the Mississippi and must be grown in sandy, low fertility, acidic soil. It will refuse to grown in heavier, compost-enriched loam, clay-loam, and clay soils. Mismatched soil is the most common reason gardeners have difficulty getting A. tuberosa to grow successfully.

Lauren Springer Ogden, renowned author, gardener, and landscape designer recommends that Orange Butterfly Weed be transplanted before the heat of summer (April-May) or in the fall. She has observed that the combination of wet roots and hot daytime temperatures favor root rot from soil pathogens. She also points out that this species is "highly soil-specific depending on the strain you grow". Lauren also relates that the plants are susceptible to pill bugs. "They will chew where the root meets the crown. And they love warm moist conditions". Another reason to not wait to plant in the heat of summer and not to mulch. This plant is happiest growing in bare, uncovered ground.

Orange Butterfly Weed is also sensitive to growing in damp soil, especially after transplanting. Yellow, chlorotic foliage is usually an indication of over-watering. I recommend that new transplants be watered thoroughly after the initial planting. After the initial watering, wait until the plant begins to wilt slightly before watering thoroughly again. Once you see new growth, a good soaking every 5 to 10 days will be sufficient. Once established, which happens in a few months, the plants may not need much additional water unless conditions are hot and dry. For those of us with drip systems, be sure to place the emitter off to the side of the planting hole so the roots won't sit in overly wet soil.

To solve this problem, High Country Gardens sells two distinct selections:

'Western Gold' is grown from seed originally collected in western CO where it grows in drier, alkaline soils. It is the best choice for drier climates with heavier, higher pH soils common in the western half of the US.
Clay form Butterfly Weed is a unique strain originally found growing in a clay field near Madison, WI where it was rescued from impending construction project. The original plant found its way into the capable hands of Neil Diboll who propagated this unique find and introduced into cultivation.

Plant Milkweed For Monarchs

Shop All Milkweed

by David Salman

Monarch aclepias syrica — Monarch Butterfly on Common Milkweed (Asclepias syrica)

Feeding Our Winged Royalty

WASHINGTON — The annual overwintering count of monarch butterflies released today shows a modest population rebound from last year’s lowest-ever count of 34 million butterflies, but is still the second lowest population count since surveys began in 1993. But the 56.5 million monarchs currently gathered in Mexico for the winter still represents a population decline of 82 percent from the 20-year average — and a decline of 95 percent from the population highs in the mid-1990s.

“The population increase is welcome news, but the monarch must reach a much larger population size to be able to bounce back from ups and downs, so this much-loved butterfly still needs Endangered Species Act protection to ensure that it’s around for future generations,” said Tierra Curry, a senior scientist at the Center for Biological Diversity.

“Despite this small increase, monarch populations are still severely jeopardized by milkweed loss in their summer breeding grounds due to increasing herbicide use on genetically-engineered crops,” said George Kimbrell, senior attorney for Center for Food Safety. “We will continue to do everything we can to ensure monarchs are protected under the Endangered Species Act.”

The butterfly’s dramatic decline has been driven in large part by the widespread planting of genetically engineered crops in the Midwest, where most monarchs are born. The vast majority of genetically engineered crop acres are in varieties made to be resistant to Monsanto’s Roundup herbicide, a potent killer of milkweed, the monarch caterpillar’s only food. The dramatic surge in the use of Roundup and other herbicides with the same active ingredient (glyphosate) with Roundup Ready crops has virtually wiped out milkweed plants in Midwest corn and soybean fields. In the past 20 years it is estimated that these once-common, iconic orange-and-black butterflies may have lost more than 165 million acres of habitat — an area about the size of Texas — including nearly a third of their summer breeding grounds.
Press release from the Xerces Society January 27, 2015. Read the entire article at www.xerces.org

Monarch caterpillar feeding on Butterfly Weed (Asclepias)

Say What?

It's truly astounding that our beloved Monarch butterfly is imperiled and faces the real threat of extinction. As American agribusiness continues it to expand the development and use of GMO, herbicide and pesticide intensive crops, we are now seeing its direct effects on the health of our natural world and the creatures that live in it.

Let's not let the Monarch become the next passenger pigeon, whose vast numbers once darkened the sky when huge flocks would fly overhead. As gardeners, we can and must make a concerted effort to reverse this loss of habitat by planting Milkweed (Asclepias) to help feed the Monarch's caterpillars put in peril by corporate profits and disregard for our planet.

A Primer To Making your Milkweed Planting Efforts Successful

While there are many species of Asclepias, a widespread genus throughout North America, it is recommended that we concentrate our efforts on growing five primary non-tropical species of Milkweed:

Monarch butterflies on Butterfly Weed (Asclepias)

Orange Butterfly Weed (Asclepias tuberosa) - a tap-rooted species that requires a fast draining sandy soil, unless you plant the clay form or 'Western Gold' forms which grow in uncompacted, non-moist clay soils.
Showy Milkweed (A. speciosa) - a fast growing stoloniferous species from the western US with large pink flower heads.
Common Milkweed (A. syriaca) - a fast growing stoloniferous species with large pink flower heads.
Swamp Milkweed (A. incarnata) - an attractive species with fiberous roots and pink or white flowers that grows in swampy to medium-moist soils.
Sullivan's Milkweed (A. sullivantii) - a rarer Mid-Western species that is slowly stoloniferous with large pink flower heads.

For the ornamental garden, Orange Butterfly Weed, Swamp Milkweed and Sullivan's Milkweed are considered the best varieties. Showy Milkweed and Common Milkweed are aggressively stoloniferous (spreading by underground roots) and are best planted in peripheral areas of the landscape such as along drainage ditches and unused portions of your property where their weediness won't be a problem.

Asclepias incarnata ‚Rose‚ (Swamp Milkweed) is a showy pink blooming Asclepias species that is a food plant for Monarch butterfly caterpillars and a nectar source for ad...
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Rose Swamp Milkweed Rose Swamp Milkweed Asclepias incarnata
As low as $13.99 Sale $12.59
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Asclepias incarnata 'Rose' (Swamp Milkweed) is a showy pink blooming Asclepias species that is a food plant for Monarch butterfly caterpillars and a nectar source for adult butterflies. Also known as Swamp Milkweed, it grows best in moist or wet soils.
Asclepias incarnata ‚Ice Ballet‚ (Swamp Milkweed) lights up the mid-summer garden with vanilla scented, pillowy clusters of snow-white flowers. Deep green foliage and whi...
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Ice Ballet Swamp Milkweed Ice Ballet Swamp Milkweed Asclepias incarnata Ice Ballet

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$13.99 Sale $11.89
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Asclepias incarnata 'Ice Ballet' (Swamp Milkweed) lights up the mid-summer garden with vanilla scented, pillowy clusters of snow-white flowers. Deep green foliage and white flowers that bloom from mid-summer to fall are the perfect backdrop for brightly colored butterflies that visit each summer. A pollinator-favorite, especially for Monarch butterflies, this easy-care milkweed is happy in a sunny spot with moist soil.
Asclepias incarnata ‚Soulmate‚ (Swamp Milkweed) lights up the mid-to-late summer garden with clusters of pink petals surrounding a white heart. This native star attracts ...
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Soulmate Swamp Milkweed Soulmate Swamp Milkweed Asclepias incarnata Soulmate

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$13.99 Sale $11.19
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Asclepias incarnata 'Soulmate' (Swamp Milkweed) lights up the mid-to-late summer garden with clusters of pink petals surrounding a white heart. This native star attracts and nourishes hummingbirds, butterflies, bees, and pollinators of many shapes and sizes – especially Monarch butterflies. With a sweet vanilla scent, it’s deer and rabbit resistant. This easy-care plant brings as much pleasure to the gardener as it does to the pollinators in sunny borders and meadows with average-to-moist soil.
Our ‘Swamp Milkweed Collection’ is the perfect start to your butterfly garden, rain garden, stream bed, or anywhere you want to see beautiful flowers and pollinators in w...
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Swamp Milkweed Collection Swamp Milkweed Collection Asclepias incarnata Collection

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$36.99 Sale $33.29
Per Collection of 3

Our ‘Swamp Milkweed Collection’ is the perfect start to your butterfly garden, rain garden, stream bed, or anywhere you want to see beautiful flowers and pollinators in wet soil. Pink and white flowers on tall stems with lovely long green leaves look beautiful in large plantings, or paired with other tall perennials. In fall, look for plentiful silky-haired seeds. Asclepias incarnata (also known as Rose Milkweed) is a native perennial, and the sole host plant of Monarch Butterflies. In time, this deer resistant plants will spread and naturalize to help your pollinator garden grow! Collection of 3 plants.

Seeding Milkweed into Your Landscape

Neil Diboll, founder of Prairie Nursery in Wisconsin, and a pioneer of prairie restoration says this about seeding Asclepias: "Seeds of all the members of the genus Asclepias that I have worked with benefit from a 30 day Moist Stratification period to break seed dormancy. The seeds germinate best under warm soil conditions. They can be successfully seeded in fall as a “dormant seeding” to improve germination in spring. (Fall planting after frost will provide necessary cold stratification.) All species (A. tuberosa, A. syriaca, A. sullivantii, A. incarnata) will also germinate moderately well when seeded into warm ground in mid to late spring with only Dry Stratification treatment."

Seeds can be moist stratified by mixing seed with moist (not soggy) sand in a zip-lock plastic bag and placed in the refrigerator for 30 days. After 30 days of cold moist storage, the seed's natural chemical germination inhibitors have dissipated and are ready to sprout. Dry stratification is done by placing dry seed in the refrigerator for 30 or more days.

Planting Potted Asclepias Plants Into Your Landscape

With exception of Orange Butterfly Weed, the other four species transplant readily as actively growing or dormant plants. Orange Butterfly Weed on the other hand has a deep growing tap-root and is much more finicky about the soil in which it prefers to grow. The most commonly available Butterfly Weed seed of this species is grown from populations originating east of the Mississippi and must be grown in sandy, low fertility, acidic soil. It will refuse to grown in heavier, compost enriched loam, clay-loam and clay soils. Mis-matched soil is the most common reason gardeners have difficulty getting A. tuberosa to grow successfully.

To solve this problem, High Country Gardens sells two distinct selections:

'Western Gold' is grown from seed originally collected in western CO where it grows in drier, alkaline soils. It is the best choice for drier climates with heavier, higher pH soils common in the western half of the US.
Clay form is a unique strain originally found growing in a clay field near Madison, WI where it was rescued from impending construction project. The original plant found its way into the capable hands of Neil Diboll who propagated this unique find and introduced into cultivation.

Lauren Springer Ogden, renowned author, gardener and landscape designer recommends that Orange Butterfly Weed be transplanted before the heat of summer (April-May) or in the fall. She has observed that the combination of wet roots and hot daytime temperatures favor root rot from soil pathogens. She also points out that this species is "highly soil-specific depending on the strain you grow". Lauren also relates that the plants are susceptible to pill bugs. "They will chew where the root meets the crown. And they love warm moist conditions". Another reason to not wait to plant in the heat of summer and not to mulch. This plant is happiest growing in bare, uncovered ground.

Easy on the Water

Orange Butterfly Weed is also sensitive to growing in damp soil, especially after transplanting. Yellow, chlorotic foliage is usually an indication of over-watering. I recommend that new transplants be watered thoroughly after the initial planting. After the initial watering, wait until the plant begins to wilt slight before watering thoroughly again. Once you see new growth, a good soaking every 5 to 10 days will be sufficient. Once established, which happens in a few months, the plants may not need much additional water unless conditions are hot and dry. For those of us with drip systems, be sure to place the emitter off to the side of the planting hole so the roots won't sit in overly wet soil.

Text and Photos By David Salman

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