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All About Milkweed

all about milkweed

By Judith Irven, gardening expert, landscape designer and writer.

Milkweeds make beautiful garden plants.

Milkweeds are classic American wildflowers that also make lovely additions to our gardens.

They are right at home in an informal sunny border, where their striking architectural structure will contrast beautifully beside some fine-textured native grasses. And, with their compelling fragrance, they are the perfect lure for many different species of butterflies—making milkweeds a wonderful addition to a ‘butterfly garden’.

Despite milkweed’s overall bold structure, their individual flowers are quite exquisite. Growing on short stalks, these delicate blossoms hang together like clusters of nodding bells—a delight for the eye as well as the nose!

Milkweeds are vital contributors to the wider environment

In summertime many kinds of butterflies and bees swarm around the milkweed flowers to feast on the nectar and, in so doing, they transfer the pollen from plant to plant (thus perpetuating the milkweeds themselves).

And—most important of all— milkweed plants are the ONLY food that the larvae of our beloved and beleaguered Monarch butterfly can eat, and thus they are the critical link in the lifecycle of the Monarchs. Without milkweeds these beautiful butterflies will completely disappear; their population has already dropped an incredible 90% over the past decade.

Learn More About Monarchs and Milkweeds.

swamp milkweed closeup
Swamp Milkweed has delicate blooms and a vanilla aroma.

Milkweed and Butterfly Weed are both members of the Asclepias family

Milkweeds all belong to the single genus Asclepias (pronounced As-KLEE-pias). They all have complex five-part flowers, and most exude a distinctive milky sap - both features that can help identify milkweeds in the wild.

tropical milkweed
Tropical Milkweed blooms in vivid reds and oranges.

Choose the Best Milkweed for Your Own Growing Conditions

The USDA data base lists 76 different milkweed species that are native to Canada and the USA. The places where the various species are found in the wild give us plenty of clues about how to grow them in our gardens.

There are milkweed species that are native to every region of the USA and southern Canada. and many are adapted to a wide range of climates.

However some species are quite particular as to their growing requirements. A few are found in swampy places, a sure hint as to where they will thrive around our homes. Others grow quite happily in arid parts of the country—choose these if you live in a dry climate or want something for an especially dry spot on your property.

Learn How to Grow Milkweed in Your Garden.

Which Milkweed is Right For Your Garden?

The most commonly available milkweeds include four species that are native across a vast swath of the continent, from the Atlantic coast to the Rocky Mountains, and from the Gulf Coast to southern Canada. Some of these milkweeds prefer wet locations but others prefer dry places. So, wherever you live and garden, there is a milkweed that will be right for you!

Common Milkweed—Asclepias syriaca: Seen in meadows across the eastern part of the United States, the Common Milkweed is a robust-looking plant with white (to-pink, to-pale-lavender) bell-like flowers. Growing between three and five feet tall (maybe taller in good garden soil), it's best placed at the back of the border. It prefers somewhat moist soil and plenty of sun, and it would look great combined with any native Switch Grass, such as Panicum ‘North Wind’.

Swamp Milkweed—Asclepias incarnata: This milkweed has rose-pink flowers and grows naturally in marshes, making it ideal for a moist spot in your garden. It would also make a great addition to a rain garden (a wide depression that collects excessive rainwater, gradually letting it be absorbed into the surrounding soil).

There are three popular varieties of Swamp milkweed for you to choose from, all growing over three feet high for a good ‘middle of the border’ placement: Ice Ballet is a recent introduction that has pure white flowers. Soulmate and Cinderella are two other new cultivars that are both quite floriferous and have deep-pink flowers. Either one would make a wonderful planting companion for Ice Ballet.

Whorled Milkweed—Asclepias verticillata: Whorled milkweed has attractive white flowers in loose clusters which open in mid-summer. It is shorter than most milkweeds, no more than thirty inches high, and it will also tolerate partial shade.

Whorled milkweed is found in dry locations across the eastern half of the continent and so will do best in a dry spot in the garden.

Butterfly Weed—Asclepias tuberosa: Butterfly weed is known for its cheery upright-facing orange flowers in mid-summer, and now it is joined by a new cultivar called Hello Yellow. As the name suggests, many kinds of adult butterflies will visit your garden to sip the nectar of your Butterfly Weed flowers. In addition, the plants will also attract Monarch butterflies for egg-laying.

Like the Whorled Milkweed, Butterfly Weed needs a dry location near the front of the border. And, since both these milkweed species are shorter in stature, they make perfect garden companions, where together their colorful white, orange and yellow flowers will make a lovely contrast. Now complete the picture with the linear texture of some Little Bluestem grasses!

Tropical Milkweed—Asclepias curassavica: Tropical Milkweed, hails all the way from South America. In colder climates across the continental USA and Canada, this one is normally grown as an annual where it will bloom from June to October. (Some people have good luck over-wintering their Tropical Milkweed indoors on a sunny windowsill). Save your seeds from the previous year and then start them indoors about eight weeks before your last frost date.

Tropical Milkweed grows up to 3 feet high. It has blood-red flowers with yellow hoods which would look lovely with a Swamp Milkweed cultivar, like Ice Ballet .

Tropical milkweed is also a great lure for Monarch butterflies where they will readily lay their eggs.

A word of warning: it is important that we gardeners do not inadvertently disrupt the annual Monarch migration patterns northward by encouraging a late hatch. So PLEASE , if you want to grow the tropical milkweed, check the date by which the Monarchs would normally leave your area for their migration northwards; and at that time cut your Tropical Milkweed plants to the ground.

Growing Milkweeds in the Garden

Is Milkweed a weed?

While the name milkWEED sounds as though these plants may be poised to take over your garden, most species of milkweed are actually very well behaved in a garden setting. And, if you are concerned about your plants self-seeding in unwanted places it's easy to remove the large seedpods just before they split open and release their seeds in the fall. And a few species, such as the western Showy Pink Milkweed— Asclepias speciosa—spread by runners and are best grown in a meadow.

Garden Design with Milkweed in Mind

Milkweeds lend themselves to an informal planting, either in a sunny border or in a meadow (which you mow back annually in the fall). Their strong texture always looks stunning in conjunction with the taller prairie grasses, such as Big and Little Bluestems, Switch grasses and Tussock grass.

butterfly weed in a garden
Butterfly Weed in the garden.
swamp milkweed
Swamp Milkweed 'Cinderella' in the garden.
butterfly weed
Butterfly Weed, ageratum, and daisies.

Another great way to use milkweed in the garden, is to install a Monarch Waystation. This specialized garden is a plant grouping that takes the entire lifestyle of the Monarch Butterfly into consideration, offering both food and habitat for every stage of the Monarch's growth. You can even have your Waystation officially registered!

Growing Milkweed from Seed

Milkweeds are quite easy to grow from seed, although it may take a couple of years before your young milkweeds plants actually flower. If possible sow the seeds in open ground in the fall, where they will naturally be exposed the normal winter’s cold. If you need to plant the seeds in the spring just place them in a moist paper towel in the freezer for a few weeks. This technique, known as stratifying the seed, mimics the cold of winter and breaks the seed’s natural dormancy.

However, if you have a small garden, or are a beginning gardener, buying milkweed plants is generally the preferred approach.

And finally, people who want to do even more to conserve Monarch butterflies are experimenting with growing their milkweeds in containers, where they can monitor the progress of the eggs, larvae and watch butterflies emerging from their chrysalides.

About the Author: Judith Irven is an accomplished Vermont landscape designer and garden writer, and she delights in helping people everywhere create beautiful gardens. You can visit her online at: OutdoorSpacesVermont.comBack to top.

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