Best Milkweed Varieties for Monarch Butterflies

The Missing Monarchs

What has happened to our Monarch butterflies? Their populations have declined by almost 90% over the past 20 years. Many factors have contributed to this horrific loss, including climate change, weather extremes, loss of winter habitat in Mexico, and widespread use of pesticides. While these are problems that will take years to change, one thing we can do in our own yards today is use less or no chemicals. A very easy thing we can do is to plant milkweed!

Not only will you help these valuable pollinators, but you’ll treasure the presence of fluttering friends in the garden!

Milkweed is the only food Monarch “babies” eat! It’s that simple. When the caterpillars hatch out, they can start feeding immediately on the milkweed leaves. Toxins in the plant make the adult Monarchs and their larvae taste bitter to predators, protecting them from hungry birds. It is such an effective deterrent that other butterflies, such as the similarly-colored Viceroy, are also avoided by predators just in case they are bitter too. If you decide to grow milkweed in your yard, be aware that the cardiac glycosides contained in the plants are toxic to pets and people also.

Milkweed Varieties

The milkweed genus (Asclepias) is fairly large, with 73 species native to the US and over 100 in North America. They support 12 species of butterflies and moths, including the Monarch. Choose milkweed species that are native to your region and are right for your environment. Here are a few to consider; they have wide native ranges and are frequently available as seeds or plants:

Common milkweed smells so sweet they should make a perfume from it!

• Common milkweed (Asclepias syriaca) is a hardy perennial that will thrive almost anywhere in the US, 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 Monarchs.

Butterfly weed is a bright spot in the garden that attracts all kinds of pollinators.

• Butterfly weed (A. tuberosa) is less aggressive than its common cousin, 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 has thinner leaves and more colorful flowers than common milkweed.

• Swamp milkweed (A. incarnata) is also more well-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.

See maps showing the native ranges of many types of milkweed.

Two No-Grows

There are some milkweeds that are not beneficial to Monarchs. Gardeners in southern states should avoid planting tropical milkweed (A. curassavica). It is a beautiful plant with bright yellow/red/orange flowers, but it hosts a parasite that infects the caterpillars and weakens the butterflies when they emerge from their chrysalis. Since the plants don’t die back until late into winter, the Monarchs stay there until it is too late to make their yearly trip to Mexico. Learn more about Monarch butterfly migration.

Black Swallow wort. If you see this growing, pull it out! (Photo from UNH Extension)

Another no-grow is climbing milkweed (Cynachum nigrum), also called black swallow-wort. It is an incredibly invasive twining weed in the milkweed family. If a Monarch lays her eggs on it, those caterpillars won’t grow large enough to turn into butterflies. It is a tough one to get rid of, since it spreads by wind-blown seeds and has a large root crown and deep roots.

Becoming a Way Station

Planting milkweed and other native wildflowers, especially late season nectar plants such as goldenrod and asters, will add to the survival chance of visiting monarchs and other pollinators by acting as an energy source and a shelter for adults, as well as host plants for larvae.

You can create a Monarch Way Station in your backyard in a 100 sq. ft. sunny space with well-drained soil. Plant at least 10 plants of two or more flower species native to your region that flower at different times, including some milkweed. Once it is up and growing, register it at MonarchWatch.org. Over 31,000 gardeners across the country have done it so far!

One reader said, “Think of it as an Airbnb for butterflies!”

Related Content

• Read our milkweed Growing Guide.
• Learn more about common uses for milkweed.
• Learn more about plants that attract butterflies.