Milkweed is a much overlooked plant in the gardening world. The many varieties of milkweed plants bloom with both subtle and bright colors, and the whole milkweed plant is vital to the life cycle of Monarch butterflies as their sole host plant, and has also been used as a food source by Native American tribes. Yet, it is often not even considered by many gardeners, perhaps because of the word “weed” in its name.
However, there’s much more to this native flower than the name suggests. Plant milkweed in your garden and you’ll get to enjoy lovely colors, enchanting fragrance, and the happy sight of bees, butterflies, and hummingbirds hovering around the flowers.
Here’s everything you need to know about milkweed plant and how to successfully grow milkweed plants in your garden.
What Is Milkweed?
Don’t let the name fool you. Milkweed (Asclepias) is actually a beautiful American wildflower and an important native plant.
There are many different varieties of milkweed plants native to different regions of the U.S., Canada, and South America. All are perennials in their native climates, but some- like tropical milkweed (Asclepias curassavica) – are annuals if grown in northern regions.
Plants flower with delicate, star-shaped blooms that will be various colors depending on which species is grown. Each milkweed also has its own fragrance and unique characteristics.
Milkweed is an important native plant that supports pollinators and especially Monarch butterflies. It’s not as showy as some ornamental plants but still deserves a place in your garden and will send up lovely, star-shaped blooms home to the beautiful Monarch butterfly.
The plants can grow to be 2-5 feet tall depending on species. Many milkweeds are suited to dry soils but some, like swamp milkweed, need moist and rich soil to grow well. Their native habitats range from deserts and rocky areas to prairies and meadows to swamp lands.
The name “milkweed” comes largely from the milky white sap that will ooze out of stems and leaves when broken. This milky substance can cause skin irritation and is toxic to dogs, cats, and other animals when ingested.
The Monarch Butterfly Needs Milkweed
The nectar of milkweed flowers attracts pollinators like native bees and honeybees, but the plant itself is a host plant especially vital to Monarch butterflies.
Now that more is understood about the Monarch life cycle and migration pattern, gardeners and conservationists have begun to understand just how important this native plant is to saving the butterfly population.
Monarchs are beautiful, orange and black-winged butterflies native to the Americas. Sadly, the Monarch Butterfly population has decreased by about 90% over the last two decades or so.
Much of this decline has been caused by the destruction of native habitats and plants, especially milkweed species. Milkweeds are the only host plants for Monarch caterpillars. The adult butterflies can feed on the nectar of a variety of plants, but the caterpillars only eat milkweed leaves.
Milkweed species are the only plants that Monarch caterpillars feed on. Without them, the entire Monarch population would be lost.
Many wild milkweeds have been lost due to the widespread use of pesticides and the destruction of their native habitats.
This means that home gardeners play an important role in stepping up to help this species of plant and the Monarch butterflies recover. By planting milkweed in your garden, you’ll be providing both nectar and leaves for Monarchs and helping to save a species!
Types of Milkweed
There are a few more commonly grown species of milkweed but over 70 in total that are native to every region of the U.S. as well as parts of southern Canada.
Here are some of the main types grown, but check with this guide to find suggestions for the region you live in:
- Common Milkweed (Asclepias syriaca)– Common milkweed is native to the meadows of the eastern U.S. It blooms with shades of white, pink, and pale lavender and grows 3-5 feet tall. Likes well-drained soil.
- Swamp Milkweed (A. incarnata)– Swamp milkweed is native to North America and a great choice for soggy or moist areas in your garden since its native habitat is swamps and marshes. The flowers are a lovely rose-pink (with different colored cultivars available) and have a vanilla-like scent. Grows 3-5 feet.
- Butterfly Weed (A. tuberosa)– Butterfly weed is a colorful orange and yellow flowered milkweed plant that attracts many species of butterflies. It likes dry soil and is smaller in stature than other varieties, growing about 2 feet tall.
Butterfly weed usually has bright orange flowers, although some cultivars are red- or yellow-flowering. This is a great milkweed species for smaller spaces, since plants top out at 2 or 3 feet.
- Whorled Milkweed (A. verticillata)– Whorled milkweed is native to prairie regions and has narrow leaves similar in shape and size to rosemary. Plants are less showy than other species, but the white flowers pair well with other more colorful milkweeds. Prefers dry soil and performs well in rocky soil.
- Showy Milkweed (A. speciosa)– This species is native to the western part of the U.S. and some regions in Canada. Showy milkweed is so named because of the explosion of pretty, fragrant blooms that come out from mid to late summer. Grows 3-4 feet tall and spreads aggressively in certain regions.
- Tropical Milkweed (A. curassavica)– Native to South America, tropical milkweed can be grown as an annual in colder USDA hardiness zones. It has bright red and yellow flowers and grows about 3 feet tall.
Cultivars to Try
Milkweed comes in a variety of heights and shades of pink, red, orange, purple, white, and yellow. Here are a few cultivars to consider for your garden:
- Asclepias incarnata ‘Cinderella’– This cultivar of swamp milkweed has large clusters of rose-pink flowers that smell of vanilla and bloom continuously from midsummer to fall.
- Asclepias incarnata ‘Ice Ballet’– This is another swamp milkweed cultivar that has fragrant, pure white blooms. Unlike other members of this species, ‘Ice Ballet’ does well in drier soils and pairs well with colorful milkweeds.
Certain species of milkweed are showier than others. For example, tropical milkweed has bright red and yellow flowers, but it can only be grown as an annual in northern regions.
- Asclepias tuberosa ‘Gay Butterflies’– This is a butterfly weed cultivar that is a mix of three colors: red, orange, and yellow. The flowerheads can reach 5 inches across and bloom from early summer until frost.
- Asclepias tuberosa ‘Hello Yellow’– As the name suggests, this is a showy yellow-golden flowering cultivar.
How to Grow Milkweed Plant
You can buy milkweed plants at your local garden center or a nursery that sells native plants, but it is also easy to grow milkweed from seed.
When growing milkweed plant, it’s important to remember that it doesn’t transplant well due to the long taproot it grows. This means you’ll want to sow your seeds or plant your seedlings in a permanent location rather than planning to move plants later.
Starting from Seed Outdoors
Milkweed seeds need a process called stratification to help them germinate. By planting seeds outdoors in late fall, you’ll be getting the winter weather to do this for you.
First, make sure you have seeds for a perennial milkweed that can be grown in your region. Tropical milkweed, for example, has to be grown as an annual in cold regions, so trying to start the seeds outdoors in the fall will be unsuccessful.
Milkweed doesn’t do well with being transplanted, so plant your seeds or seedlings in their permanent location from the beginning. Seeds start easily when sown outdoors in the fall and can also be started indoors.
Then, when you are ready to sow seeds, start by getting your garden area ready. Work through the soil to break up clumps and get rid of rocks, weeds, and other debris.
Mix in some compost if necessary to improve soil texture and drainage.
Sow your seeds in the area you want the plants to grow permanently. You can do this by scattering them on the surface of your prepared soil and covering them lightly with more soil to keep the seeds from washing or blowing away.
There’s no need to water your seeds, since nature will take care of that for you during the coming months.
Start checking on your garden area in the spring. When seedlings start coming up and get a few inches high, you can thin them to the correct spacing for the variety you’ve planted. Remove or secure seed pods before they split open if you don’t want the plant to spread throughout your garden.
Starting from Seed Indoors
As an alternative to sowing outdoors in the fall, you can also start seeds indoors in early spring. You’ll want to get your seeds started 4-8 weeks before you plan to transplant them outside.
Before actually sowing the seeds, you can mimic the winter conditions that break down the seed coat to improve germination. Get a paper towel wet, squeeze it out, and place your milkweed seeds on it in a single layer. Fold it over or place another wet paper towel over top.
Put the seeds and paper towels in a plastic bag and seal it shut. Keep this plastic bag with your seeds in the refrigerator for 1-2 months.
When it’s time to plant your seeds, prepare a seed starter flat or cell packs with already moistened soil. Use a good quality seed starting mix for best results. Sow the seeds about ¼ inch deep and cover them over with soil.
Water your seed trays well and leave them in a warm place to germinate. Most milkweed seeds start to germinate in 7-10 days.
Once your seeds sprout, place the flats under grow lights or by a sunny window. Make sure they get good airflow to prevent damping off, and keep the soil watered but not soaking wet.
When the seedlings are about 3-6 inches tall, they can be transplanted outside. First, however, you’ll want to gradually accustom them to the weather outdoors by taking them outside during the day and back in at night.
Most types of milkweed need to be planted in full sun (meaning areas that get a minimum of 6-8 hours of sunlight a day).
DIfferent species of milkweed prefer different soil types, but most varieties are tolerant of poor and imperfect soil conditions. Most species- with the exception of swamp milkweed- prefer dry and at the very least well-drained soil.
Plant milkweeds in full sun to ensure that they grow and flower well. Once established, plants are very low maintenance and will start attracting butterflies as soon as they bloom.
Spacing will also depend on the species and cultivars you’re growing. Butterfly weed, common milkweed, and whorled milkweed should be spaced at least 18 inches apart. Swamp milkweed will eventually form a large clump and is best spaced 2-3 feet apart.
For the purpose of helping Monarch butterflies, you should plan to plant in groups to make it easier for the butterflies to find the milkweed. Planting several varieties is also a good idea.
Once you have your planting area(s) and spacing figured out, you can plant your milkweed outdoors after all danger of frost has passed.
Dig holes that are slightly deeper and 1-2 times as wide as the root ball of your plants. Place the plants in their holes so that the top of each root ball is just level with the soil line. Fill in around each plant with soil and firm it down with your hands.
Water your new transplants well and give them water as needed for the next week or two until they get established.
Milkweed Plant Care
Caring for milkweed plants is easy since they are very low maintenance.
Swamp milkweed will likely benefit from a layer of mulch to keep the soil moist and weeds down. Most other milkweed species prefer dry conditions and will do better without any mulch.
Seed pods will form on plants after flowering, typically in the fall. If you want to prevent the seeds from sprouting in your garden, clip off the seed pods before the seed pods have a chance to open.
Because they are native plants, there’s no need to fertilize milkweed, and plants will likely do better without it. You can topdress the soil with compost every year to add some extra nutrients, but using a store-bought fertilizer isn’t necessary.
Milkweed spreads both by seed and by underground rhizomes. If you want to keep it spreading by seed, clip off the seedpods before they have a chance to mature and drop. Otherwise, leave them on for interest and wildlife.
Do not attempt to dig up and divide or transplant established milkweed plants. They develop long tap roots that don’t respond well to being disturbed.
If you want more milkweed plants, you can easily collect the seeds in the fall and sow them elsewhere in your garden.
Pests and Diseases
Established milkweed plants are rarely affected by pests or diseases. Occasionally, they will be bothered by aphids or whiteflies, which you can hose them off with a strong jet of water.
If you see white, yellow, and black-striped caterpillars crawling on your milkweed plants and eating the leaves, congratulations! Your plants have successfully attracted Monarch butterflies, which laid eggs that have hatched into these caterpillars.
This little critter is a Monarch caterpillar. You can recognize them by their distinctive yellow, white, and black stripes as well as by the two black antennae or tentacles that come out of the head.
Make sure you leave the caterpillars alone to eat in peace. They won’t cause enough damage to harm your plants, and they will one day hatch into beautiful butterflies.
What to Plant With Milkweed
Milkweed works well with a variety of annual and perennial plants, especially other natives. Here are some ideas for what to do with it in your garden:
- Milkweeds make great plants for a sunny border. They have a more informal than formal look and do well with similar plants. Most varieties should go towards the back of the border because of their height.
- Milkweed is a perfect nectar-rich plant for a butterfly garden. Mix it in with other nectar sources like goldenrod, asters, Shasta daisies, purple coneflower, Rudbeckia, and bee balm.
- You can plant a variety of milkweed species alongside ornamental grasses, like the Bluestems, for a naturalized prairie look. Add in some goldenrod or black-eyed Susans to complete the look.
- For a contrast, pair milkweed with blue, purple, or rose-colored perennials like asters, cool colored salvias, and balloon flowers.
There are lots of ways to use milkweed in your garden landscape so that both you and the Monarchs can enjoy it! With your help, both milkweed plants and Monarch butterflies can make a comeback with your butterfly garden. The plant is also a food source for Native American tribes.