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How to Grow Milkweed: The Complete Plant Guide

Photo Credit
Lmmahood/Getty Images
Botanical Name
Asclepias spp.
Plant Type
Flower
Sun Exposure
Full Sun
Soil pH
Slightly Acidic to Neutral
Bloom Time
Spring
Summer
Flower Color
Orange
Pink
Purple
White
Hardiness Zone
3
4
5
6
7
8
9
Special Features
Attracts Butterflies

Planting, Growing, and Caring for Milkweed

Catherine Boeckmann
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Milkweed (Asclepias) is a native wildflower we should all grow for the butterflies—specifically Monarchs! The Old Farmer’s Almanac will help you choose your milkweed plants, explain when and how to plant, and instruct you on after-season care.

About Milkweed

Several popular species are suited for cultivation in the garden. Common milkweed (Asclepias syriaca) is the best-known of the over 100 perennial milkweeds native to North America. Milkweed plants support 12 species of butterflies and moths, including the Monarch butterfly.

The nectar in all milkweed flowers provides valuable food for butterflies, bees, and other pollinators. Butterflies don’t only need nectar but also need food at the caterpillar stage. The leaves of milkweed plants are the only food monarch caterpillars can eat. Plus, monarch butterflies also need the milkweed plant to lay their eggs on.

Self-sowing milkweed before flowering! Credit: Catherine Boeckmann
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Planting

When to Plant 

  • Milkweed can be grown from seed or transplants.
  • Start seeds indoors about 4 to 8 weeks before your last frost date in the spring.
  • Alternatively, sow seeds directly into the garden soil in the fall or in early spring. 

Where to Plant

  • Milkweed plants require full sun.
  • Milkweed does best in well-draining soil, although some species, like swamp milkweed, prefer to grow in soil with higher moisture levels.
  • Plant in the back of flower beds or create a bed for just milkweed. They can grow quite tall and need lots of space for their deep root systems to spread. They do NOT like to be transplanted.
  • Consider planting low-growing perennials 
  • Plant low-growing perennials in front of the milkweed.

How to Plant 

  • If you plant from seed, scatter seeds on top of the soil and cover with about ¼ inch of additional soil. Seeds will germinate in 7 to 10 days. Thin seedlings to 2 inches apart.
  • If you buy small plants, choose healthy specimens with well-developed root systems. Gently loosen the roots a bit before planting.
  • Plant to plant transplants in blocks rather than long rows. Space milkweed 18 to 24 inches apart.
  • Dig a hole that’s two times as deep and wide as the rootball of your plant. There is no need to amend healthy soil or amend it with a little compost.
  • Plant with the top of the root ball even with the soil line, and fill the rest of the hole with extra soil and firm up the area.
  • Water after planting to compress the soil and keep the soil moist until plants are established.

Growing

How to Grow Milkweed

Do not worry if the plants take time to get going. They stay dormant longer than most plants but should start leafing out in late spring or early summer. Avoid watering during dormancy. If they don’t flower in the first season, their leaves still provide a food source for Monarch babies.

  • Common Milkweed and Butterfly Weed need little water and thrive in a drier environment. Swamp and Tropical Milkweed need to be watered but not overwatered 
  • Water plants if the soil is dry, but avoid overwatering (especially during early dormancy).
  • The good news is that milkweed is otherwise left alone. Do NOT fertilize, spray, or prune. 
"Butterfly weed"
Butterfly weed, Asclepias tuberosa. Photo by NNehring/Getty Images.

Types

  • Common milkweed (Asclepias syriaca) is a hardy perennial that will thrive almost anywhere in the United States, especially east of the Rockies and into Canada. It needs sun, reaches 2 to 6 feet tall with wide, gray-green, velvety leaves, and is an aggressive grower. Don’t plant this in your flowerbed, or it will take over. It has a wide-spreading root system and needs an area all its own, where it can really stretch out. It has pale purple-pink flowers that are very fragrant and attract many pollinators in addition to Monarch butterflies.
  • Butterfly weed (A. tuberosa) is less aggressive than the common milkweed, growing only 1 to 2-1/2 feet tall. It is commonly grown in gardens, adapts well to moist or dry soil, and its orange flowers are very showy. It likes full sun and is hardy in Zones 3 to 9.
  • Swamp milkweed (A. incarnata) has thinner leaves and more colorful flowers than common milkweed. It is better-behaved than common milkweed, forming clumps rather than spreading out. It grows 2 to 4 feet tall, has deep rose-pink flowers, and is shade tolerant. It will grow in wet soil near lakesides or damp marshlands, but also grows well in average garden soil and is hardy in Zones 3-9.
  • Showy milkweed (A. speciosa) is native from west of the Mississippi into California and north to Canada. It has pastel pink flowers on 2- to 4-foot tall plants. It is drought tolerant, making it a good plant for arid plains and prairie-lands, though it grows well in moist garden soils as well. It needs full sun and is hardy in Zones 3-9.

Harvesting

Once established, milkweed does NOT like to be transplanted or divided.  If possible, leave milkweed alone. 

If you are bothered by the plants’ more scraggly looks or half-eaten leaves late in the season, remember to plant them at the back of your garden (or in their own space) and low-growing perennials in the front to hide the milkweed stems.

As with many native plants, milkweed will self-seed which is a free and natural way of spreading Monarch food. If you do NOT want milkweed spreading in your garden bed OR you’d like to plant some milkweed in a different location, you can remove the seedpods (before they burst open) and scatter the seeds elsewhere. 

You can also propagate milkweed from cuttings and give the plant to friends!

Propagating Milkweed from Cuttings

  1. Cut fresh green stems (1/3 inch diameter) from young milkweed plants.
  2. Recut the stems underwater and coat the bottom of the stems with rooting hormone. 
  3. Place the stems in moist sand, vermiculite, or potting soil. 
  4. The stem cuttings will root in 6-10 weeks and will be ready to be transplanted outdoors. 
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Wit and Wisdom

  • The genus name, Asclepias, commemorates Asklepios, the Greek god of medicine.
  • Native Americans taught early European settlers how to cook milkweed so that it could be safely eaten. 
  • The milky white sap was applied topically to remove warts, and the roots were chewed to cure dysentery. 
  • Infusions of the roots and leaves were taken to suppress coughs and used to treat typhus fever and asthma.
  • The stems’ tough, stringy fibers were twisted into strong twine and rope, or woven into coarse fabric.
  • Inside milkweed’s seed pods is fluffy white floss attached to brown seeds. The floss was used to stuff pillows, mattresses, and quilts, and was carried as tinder to start fires. 
  • Milkweed is the state wildflower of Illinois. 
"Milkweed seedpods"
Milkweed seed pods

Pests/Diseases

Milkweed isn’t severely affected by pests, diseases, or problems. You are most likely to see aphids enjoying the nectar! Just squirt with a water hose (but be careful to check for Monarch eggs!). 

  • Aphids
  • Milkweed leaf beetle
  • Milkweed tussock moth
  • Red and black milkweed bugs
Flowers
About The Author

Catherine Boeckmann

Catherine Boeckmann loves nature, stargazing, and gardening so it’s not surprising that she and The Old Farmer’s Almanac found each other. She leads digital content for the Almanac website, and is also a certified master gardener in the state of Indiana. Read More from Catherine Boeckmann
 

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Comments

Peggy Jack (not verified)

2 months 2 weeks ago

I live on Long Beach Island in NJ USA. I want to plant milkweed on the sand dunes. We are on the monarch route. How do I plant in sand?

Hi Peggy,

While common milkweed does perform well in sandy soils and poor soils, it does need soil in order to thrive. If you do want to plant milkweed for migrating monarchs, you could do so in some containers.

There is a variety of milkweed, sandhill milkweed, that can be planted in sand dunes, but it is native to the southeast and only winter hardy in Zones 8 and 9.

CB (not verified)

1 year 4 months ago

I had a few "freebie" common milkweed plants pop up in my small round swamp milkweed garden this spring. So I let them grow. (all for the love of Monarchs, right?) Anyhoo, boy did they grow. They're way taller than me now! When in bloom they attracted bumblebees, honeybees, butterflies, etc. However, to my dismay, I noticed honeybees dead (quite a few of them) on the flowerheads. I KNEW they were not subjected to any poisons so I reached out to my local conservation dept. I was told that it is quite common for the honeybee's feet to become trapped in the flower. They cannot get their feet out, then starve to death! I thought OMG, how horrible! I will be taking out/perhaps transplanting the common milkweeds elsewhere (somewhere that I cannot see the dead honeybees next season) because not only does it break my heart to see them dead on the flowerheads, the common milkweed has pretty much shaded and took over my small pollinator garden. The conservation dept. told me that this does not contribute to the honeybee's decline, but it sure is upsetting to see the dead bees!

Susan (not verified)

1 year 4 months ago

I planted some common milkweed in my flower beds. YIKES. I didn't know they were so invasive. I do not want them in my flower bed because the roots spread underground and they pop up every where. I dug up alot of them last year, bur they keep popping up everywhere in my flower bed. HOW I do I get them completely out of my flower beds?

Teri (not verified)

1 year 5 months ago

We put a milkweed plant in our flowerbed for the first time this year. The branches to the plant are bowing out a lot. I am wondering if I should bring them back in toward the center stem with some twine and use a dowel rod to stabilize it?
Thank you!

I have had to stake ALL of my milkweeds. Common and swamp both.

Hi Teri-

The milkweed will be healthy if it bows, but if you prefer to have it upright, please go ahead and stake it.

Thanks!

Linda Shaw (not verified)

2 years 2 months ago

Unfortunately, I planted a milkweed in a small bed next to my porch. It is too large and I want to move it out to my creek bed, the ideal place to grow as large as it can. How do I transplant a full-grown plant? And the leaves are mottled brown instead of a nice green color - what do I treat with to restore plant to good health?

Carefully dig around the base of the plant, starting 7-8 inches out from the stems. You’ll want to capture as much of the root ball as possible, so dig carefully. Once you’ve loosened the plant, carefully lift it, retaining as much of the root ball and soil as you can. Plant it in its new home and water well. If rains are infrequent, be sure to keep the plant watered until hard frosts set in.

It’s possible that the browned leaves are simply a symptom of drought or the end of the growing season, so just keep an eye on it when it pops up in the spring to see if the foliage looks as it should.