By Judy Stout
Milkweeds are famous for their association with monarch butterflies. Monarch butterflies depend on many different milkweed species for food and breeding sites. Monarchs lay their eggs on a milkweed plant and, once the larvae hatch, the caterpillars have a ready source of food provided by the milkweed plant’s foliage.
Because of a decline in monarch butterfly populations, more and more home gardeners are making milkweed plants a part of their garden design. The loss of habitat and host plants resulting from agricultural, industrial, and residential developments is having a direct impact on monarch butterfly populations.
Many gardeners are only familiar with one or two species of milkweed but there over a hundred species that occur in nature; many with interesting growth habits and flower forms that make them ornamental as well as helpful to monarchs and other creatures seeking pollen and nectar. You can add interest to your flower garden by incorporating different types of milkweed as well as entice a variety of insect species that are attracted to the flowers and foliage.
Guide to Planting and Caring for Milkweed
1. Choose the Right Location for Milkweed
Select a sunny spot in your garden with well-draining soil to plant milkweed. Ensure the area receives at least 6 hours of sunlight daily.
2. Prepare the Soil
Before planting, loosen the soil and remove any weeds or debris. Milkweed thrives in soil that is nutrient-rich and well-draining.
3. Planting Milkweed Seeds
Scatter the seeds on the soil surface and lightly press them into the ground. Water gently to keep the soil moist but not waterlogged. Regular watering is crucial, especially during the initial growth stages. Purchasing potted plants is a great way to get a jump on the growing season. More and more retailers are starting to offer milkweed plants as the interest in landscaping with natives continues to grow. You can also start seeds in pots for transplanting later.
4. Caring for Young Milkweed Plants
Once seedlings emerge, thin them out to ensure proper spacing between plants. Water regularly, especially during dry periods, but avoid overwatering. Most established milkweed plants display good drought tolerance, so they don’t require routine watering as they become more mature.
5. Milkweed Pests and Diseases
Common pests that may affect milkweed include aphids and milkweed bugs, while diseases like powdery mildew can also occur. To manage these issues naturally, consider introducing beneficial insects or using organic remedies such as neem oil.
6. Pruning and Maintenance
Milkweed plants don’t require much maintenance. You can trim back any dead or damaged foliage through the season to keep plants tidy. Take care not to remove leaves that are being damaged due to the feeding of monarch caterpillars until you are certain that the feeding season is complete. The caterpillars will feed on the leaves until it is time to progress into their chrysalis stage. Milkweed plants can be cut down in the fall.
7. Propagating Milkweed
If you live in a residential area you will probably want to remove the seed pods before they mature and split. The seeds are attached to fine, fluffy white fibers that creates a “parachute” that allows seeds to travel with the wind. This tuft of fine floss on the end of each seed is known botanically as a “coma”. Once released, the airborne seeds can drift great distances and become an unwanted weed in your neighbor’s home gardens.
You can plant fresh milkweed seeds directly in the ground in the fall and the seedlings will emerge the following spring. Milkweed seeds should be collected when the pods have ripened but before they split open. You may also save the mature seeds to plant more milkweed in your own garden in the spring however, the seeds will require at least 30 days of cold stratification before planting to improve germination. This can be as simple as storing the seeds in your refrigerator for a period of time.
Most species of milkweed can also be propagated by root division. Mature plants (aged 3 years or more) can be divided in late fall.
Designing a Milkweed Garden for Monarch Butterflies
Ongoing research is providing tips for the best way to arrange and space milkweed plants to attract the most monarch butterflies and facilitate their life cycles. Follow these tips to ensure monarch butterflies can find and easily access your milkweed plants.
- Plant milkweed plants around the perimeter of a flower garden rather than mixing it with other types of plants. It’s tempting to use tall milkweed species as a focal point in a garden, but research suggests that more monarchs will visit if the plants are grown as an isolated group or on the side of a mixed flower border.
- Try to plant milkweed in a space that will allow monarch butterflies to approach from a northerly or southern direction without encountering any big objects obstructing their flight. This might include buildings, tall fences, or large evergreen trees.
- The more visible the milkweed plants are, the better. Milkweed plants that are hidden by surrounding plants, or crowded with other, non-host plants will not attract as many monarchs.
- Apply mulch around milkweed plants to help them stand out visually to a butterfly passing by high overhead. A darker mulch is preferred such as compost or shredded bark to make the milkweed plants stand out from other nearby plants.
By following these tips and being attentive to your milkweed plants’ needs, you can ensure successful growth while creating a supportive habitat for pollinators in your garden.
10 Popular Species of Milkweed for Supporting Monarch Butterflies
There are many species of milkweed native to North America. Some have a relatively small native growing range. Here’s a rundown of milkweed species that are common over fairly large regions of North America. By choosing species native to your growing range you can support monarch butterflies as well as improve the ecosystem for all your local native wildlife. If you have the space, planting more than one milkweed species will offer monarch’s more options over a longer season. Different species may have slight differences in flowering time or other characteristics that might appeal a monarch’s preferences for where to lay eggs depending on the time of season.
Tall Milkweed Species
Tall milkweed species are ideal if you have large, wide-open spaces. Monarchs are drawn to tall milkweed varieties because they are easier to spot from a distance, when a butterfly is flying overhead.
1. Swamp Milkweed (Asclepias incarnata)
Height: 3-5’ (.9-1.5m)
USDA Zones 3-9
Swamp milkweed is a robust plant with sturdy stems and bold, lance-shaped foliage. This is a native perennial that can be found growing in moist fields, meadows, bogs, marshes, ditches, and along stream banks throughout most of North America. It’s an excellent host plant for monarch and queen butterflies.
Plants produce colorful pink flower clusters with an enchanting vanilla scent. Flowers are followed by erect seed pods up to 3-4” (20cm) long. This milkweed species thrives in constantly wet areas where most plants would fail, making swamp milkweed a good choice for poorly draining clay soil. Aphids are attracted to swamp milkweed and generally don’t do much harm. If populations are heavy, occasionally spray down the plant with water to wash them off and disrupt the insect activity.
2. Common Milkweed (Asclepias syriaca)
Height: 4-6’ (1.2-1.4m)
USDA Zones 3-9
Common milkweed is considered to be one of the very best host milkweed species for monarch butterflies. This is a North American native plant that prefers an open, sunny space to grow its best. In the wild it can be found in prairies, fields, and glowing along roadways. The ball-like clusters of fragrant flowers attract an array of pollinating insects throughout the summer. Blooms are followed by interesting, lightly spiny seed pods up to 5” (13cm) long. Common milkweed readily reseeds itself. The seeds are attached to a white fluffy fiber that creates a “parachute” for the wind to disperse the seeds over a wide area. To control spread, remove the pods before they split.
3. Showy Milkweed (Asclepias speciosa)
Height: 2-3’ (.6-.9m)
USDA Zones 3-9
Showy milkweed, as its common name implies, makes a bold statement in the landscape. The distinctly upright plants produce attractive, broad, velvety gray-green leaves. Umbels of fragrant, lavender-pink flowers appear from late spring through the summer followed by large, 3-4” (7-10cm) seed pods. A deep taproot provides this milkweed species with some tolerance to drought, but plants prefer moist soil.
Showy milkweed is a perennial plant, native to central and western regions of North America. It thrives in meadows, prairies, open spaces along roadways, and disturbed areas such as landfills or construction sites. This is one of the best host plant species for monarch butterflies providing a place for females to lay eggs and a food source for caterpillars. Indigenous peoples have a long history of using the fibers from showy milkweed to make rope, nets, and a course fabric.
4. Tall Green Milkweed (Asclepias hirtella)
Height: 2-3’ (.6-.9m)
USDA Zones 4-8
Tall green milkweed is an excellent native plant choice when creating a bee and wildlife habitat, especially since its numbers are declining in the wild. This is a durable perennial plant native over a large range of mid North America. Plants produce very attractive round clusters of pale green to white blooms in summer. The flower clusters emerge directly from the single tall, unbranched, sturdy stems followed by 4-5” (10-12cm) long seed pods. The long, narrow leaves of this milkweed species add interesting texture to the landscape. A long tap root allows tall green milkweed to survive drought conditions. Tall green milkweed is a good host plant for monarch butterflies and offers many insects a source of pollen and nectar when in flower.
5. Purple Milkweed (Asclepias purpurascens)
Height: 2-3’ (.6-.9m)
USDA Zones 3-9
Purple milkweed is a rugged perennial plant native to a large region of North America from the Midwest to the east coast. This is one of the more colorful milkweed species with rich deep pink to purple flower clusters that have an attractive rounded form. Purple milkweed is a good alternative to common milkweed if space is a problem. It’s a host plant for monarch butterflies but also supplies pollen and nectar for bees and other insects.
Low to Medium Height Milkweed Species
These shorter milkweed species may be better choices if you have a modest sized suburban garden or small urban space.
1. Green Milkweed (Asclepias viridis)
Height: 1.5-2.5’ (.4-.7m)
USDA Zones 5-9
Green milkweed, also known as spider milkweed, is an attractive, medium-sized milkweed species native to central regions of the United States from the Midwest to the South, where it can be found growing in open spaces such as prairies, ditches along roadways, and pastures. This perennial produces upright stems of broad oval leaves that make a bold statement in the landscape. Clusters of pale green to white flowers appear in summer followed by thin pods up to 5” (cm) long. The seeds are attached to a white fluffy fiber that creates a “parachute” for the wind to disperse the seeds over a wide area. Green milkweed plants may go dormant as early as early July in some regions, which means they are unlikely to be visited by monarch butterflies due to the timing.
Green milkweed also has the common name “spider milkweed” because of the crab spiders that like to reside on the plant, probably in search of prey. This species is a favorite of large and small milkweed bugs (Oncopeltus fasciatus and Lygaeus kalmia). Milkweed bugs can cause considerable damage in a short period of time, including destroying the seeds.
2. Antelope Horns or Green-flowered Milkweed (Asclepias asperula)
Height: 1-2’ (.3-.6m)
USDA Zones 5-9
Antelope horns milkweed is an attractive, clump forming perennial with long, thick, narrow leaves. Produces clusters of very interesting whitish-green flowers in spring and sporadically through the summer and fall. This North American native can be found in meadows, prairies, and along roadways in the southwestern region of the United States. The tips of the seed pods tend to curve as they mature, leading to the common name “antelope horns”. Aphids are attracted to this milkweed species but generally don’t do much harm. If populations are heavy, occasionally spray down the plant with water to wash them off and disrupt the insect activity.
3. Butterfly Weed (Asclepias tuberosa)
Height: 18-24” (45-60cm)
USDA Zones 4-9
Butterfly weed, also known as orange milkweed, is a native perennial plant that can be found growing in prairies, fields, and along roadways over a wide range of North America. This is one of the more colorful milkweed species with its bright clusters of orange flowers that appear from late spring to late summer. An interesting characteristic of butterfly milkweed is that it is the only Asclepias species that has clear sap versus milky sap. Butterfly weed makes a long-lasting cut flower for a garden bouquet.
Studies indicate that while this milkweed is popular with bees, it’s not as effective for attracting and supporting monarch butterflies. Researchers suspect it may have to do with the plant’s smaller size that makes it less visible to monarchs flying overhead.
4. Whorled Milkweed (Asclepias verticillata)
Height: 1-3’ (.3-.6m)
USDA Zones 4-9
Whorled milkweed produces clusters of small, fragrant greenish-white flowers from late spring into summer followed by 3” (7cm) long seed pods. The leaves are quite narrow, produced in whorls around the main stem, and add interesting texture to garden plantings.
Whorled milkweed is an attractive North American native milkweed species, but you’ll want to give it some space as it can spread aggressively by suckering. Planting in part shade can slow it down a bit. In the wild this plant can be found in open meadows or fields, woodlands, along roadways, and on bluffs in the central and eastern regions of North America. It’s a good host plant for monarch butterflies but offers many insects a source of pollen and nectar when in flower.
5. Narrow Leaved Milkweed, Mexican Whorled Milkweed (Asclepias fascicularis)
Height 1-3’ (.3-.6m)
USDA Zones 6-10
Narrow-leaf milkweed is a perennial plant native to the Western United States and Baja California where it is found in a variety of wild habitats from woodlands and deserts to abandoned farms and along roadways. In addition to being a valuable host plant for monarch butterflies (providing a food source and egg-laying habitat) this milkweed species has a long history of uses by indigenous peoples who used the plant fibers for making fabric and ropes. Many nectar-seeking insects are drawn to the clusters of lavender and white flowers that are produced from late spring into summer. The leaves are quite narrow and provide interesting texture to the landscape. Note that this species is toxic to dogs and cats.
Avoid Growing Tropical Milkweed
While tropical milkweed (Asclepias curassavica) is an attractive ornamental plant and attractive to monarch butterflies as well, it is not native to North America. This milkweed species originates in Central and South America and the Caribbean. It has been embraced as a showy garden flower, but it has not only become naturalized throughout the world, it is now considered invasive in many regions.
Unfortunately, the tropical milkweed species can harbor a protozoan parasite (Ophryocystis elektroscirrha) that can interfere with a monarch’s growth, reproduction, and general health; including its ability to fly. In fact, in 2022 the California Department of Food and Agriculture banned the sale of non-native tropical milkweed in the state of California in an effort to encourage the planting of native milkweed species and reduce the impact of the tropical milkweed plant on monarch butterflies.
Plants that Support Butterflies
Monarch butterflies are not the only butterfly species being impacted by the overall loss of native habitats and impacts of climate change. Discover more plants you can grow to support specific butterfly species in our article on Pairing Garden Plants with Butterflies.
0 Comments