Planting and Growing Milkweed
Welcome endangered monarchs and other beautiful butterflies to your yard with milkweed. We tell you how, when and where to grow different types of milkweed — including butterfly weed, common milkweed, swamp milkweed and showy milkweed — as well as where to get milkweed seeds.
Ready to grow some easy-care beauty? Include native plants like milkweed in your landscape. Milkweed plant is a classic native that brings a bonus: It’s a butterfly favorite. In fact, monarch butterflies rely solely on milkweed plants to feed their caterpillar young, and the loss of this plant through habitat destruction has led to monarchs recently being officially listed as an endangered species. Growing milkweed in your own garden will help.
There are several types of milkweed found across the country, with four species growing in most states. That means there’s a milkweed that’s already adapted to thrive in the conditions your garden offers. Butterfly weed (Asclepias tuberosa) is probably the most common milkweed plant tucked into landscapes. It prefers dry soil. Common milkweed (Asclepias syriaca) usually grows along roadsides and in wild spaces like meadows. It prefers average soil and tends to spread rapidly. Swamp milkweed (Asclepias incarnata) is the go-to choice for wet soil. It does well in rain gardens or low spots that tend to stay damp.
What milkweed plants bring to the garden party — in addition to luring butterflies — are beautiful blooms and fuss-free personalities. Milkweed plants are perennials, which means they’ll return year after year to grace your garden with color. These native bloomers are heat- and drought-tolerant, withstand poor soil and generally don’t need much care once they’re established. Milkweed plants are ideal for wildlife, butterfly, earth-friendly or pollinator gardens.
Milkweed Plants 101
Generally speaking, milkweed plants grow best in full sun — that means 6 to 8 hours of sun a day. Full sun yields the most flowers and stocky stems that don’t need staking. Milkweed plants grow a deep tap root. When you choose a planting spot, give it some thought, because this is one perennial that you can’t just pop out and relocate on a whim. Once that tap root sinks, your plant should stay where it’s put.
Because milkweed plants grow deep tap roots, they are slower to appear in spring. Other perennials may be up 4 inches or more in spring while milkweed slumbers on, not emerging until late spring or even early summer. In mixed planting beds or borders, it’s a good idea to mark the spot where milkweed grows to avoid disturbing plants.
Plant size and hardiness vary based on the type of milkweed you’re growing. Bright butterfly weed (Asclepias tuberosa) forms clumps 2 to 3 feet tall and wide, while swamp milkweed (Asclepias incarnata) soars 3 to 5 feet tall.
Where to Get Milkweed Plants and Seeds
You’ll find milkweed plants for sale at garden centers and nurseries. Butterfly weed (Asclepias tuberosa) is the most widely available milkweed, followed by tropical milkweed (Asclepias curassavica). You may have to visit specialized native plant nurseries to find some of the other types of milkweed.
Many times you can find dormant milkweed plants for sale in late summer at garden centers. The pot may look empty or it may have a scraggly plant, but if you can get it in the ground at least six weeks before fall frost, it should take off and stage a flower show the following growing season.
How and Where to Plant Milkweed
If you’re starting with a milkweed plant in a pot, transplant it in the garden before your region’s rainy season (spring in temperate zones, fall in warmer zones). Milkweed grows easily from seed. The simplest path to success is to sow seeds in fall. Space them roughly 1/2 inch apart and cover them with 1/4 inch of soil. Water, and let winter provide the cold treatment seeds need to break dormancy and sprout.
Julie Martens Forney
The monarch butterfly — this one on butterfly weed (Asclepias tuberosa) — relies solely on milkweed plants to feed their caterpillar young.
How you arrange milkweed plants in the garden influences how easy it is for butterflies in general — and monarchs in particular — to find the plants. Creating drifts of six or more milkweed plants means monarch butterflies will spot them more quickly. If your goal is to host monarch butterflies in your yard so they’ll complete a full life cycle (lay eggs, hatch into caterpillars, form a chrysalis and emerge as butterflies), then plant as many milkweed plants as you can.
Types of Milkweed Flowers
All milkweeds unfurl nectar-rich flowers that nourish pollinators, including butterflies of all kinds, honey bees, native bees and hummingbirds. Many individual florets (tiny flowers) combine to create what’s known botanically as an umbel (the big flower you see) on plants.
Common milkweed flowers (Asclepias syriaca) have up to 100 florets arranged to form a sphere that dangles from plants. One plant usually opens up to 30 flowers in shades of pink and white.
Butterfly weed (Asclepias tuberosa) opens flat flowers that measure 2 to 5 inches across and make a perfect landing pad for butterflies. Each flower contains up to 25 tiny florets and may feature hues of brilliant orange, yellow or red.
Swamp milkweed (Asclepias incarnata) unfurls flat to spherical flowers from 2 to 4 inches across with 20 or more florets per bloom. Flower colors include pink, white and purple tones.
After milkweed flowers fade, they form upright seedpods. If you remove seedpods, plants will flower again about a month later. At first it’s easy to handpick or snip seedpods as they start to form. Once florets toward the outer edges of the umbel (flower cluster) start to form pods, clip the whole flowering stem back to the first set of leaves below the flower stem. This is the easiest way to promote a second flush of flowers.
If you allow seedpods to mature, seeds will parachute through your yard, carried on the wind by silky threads. Milkweed plant types spread at different rates — some are prolific spreaders; others are not. To avoid a potential problem of unwanted seedlings, remove seedpods before they burst open.
In fall, leaves on milkweed plants fade to yellow shades before dropping from plants. Most gardeners leave milkweed stems in place through winter, cutting them back in spring before new growth appears. Milkweed stems are fibrous and need to be clipped — you can’t just pull them free or you risk tearing up new shoots.
There aren’t any serious pests or diseases that really affect mature, established milkweed plants. Oleander or milkweed aphids can infest at various times of the year, but they’re really only a threat to milkweed seedlings. Milkweed bugs are orange or red and black and feed on leaves, stems and seeds of milkweeds. Milkweed beetles and swamp milkweed beetle eat the leaves of these plants, but don’t seriously harm the plants.
Like monarch butterflies, if you plant milkweed, these critters will come at some point. Save Our Monarchs provides a great resource page to help you identify these insects.
Monarch caterpillars will munch their way through milkweed plants without missing a beat. When monarchs come, they will lay eggs, and the ensuing caterpillars can make a stand of milkweed or butterfly weed look pretty ragged. The best approach is to plant multiple patches of these plants. If one is in a prominently visible area, you can always shift caterpillars by hand from the visible patch to the less visible one. But it’s actually fun to watch the caterpillars grow bigger by the day and it’s a great teaching tool for kids.
Types of Milkweed
There are many types of milkweed plants available. These are a few of the more popular species you might find for sale.
- Butterfly weed (Asclepias tuberosa) — Extremely ornamental type of milkweed. Grows 2 to 3 feet tall and wide. Flower colors include orange, gold-orange or a mix of orange, red and yellow. Hardy in Zones 3-9. If you’re only growing one milkweed, this is the one to try.
- Swamp milkweed (Asclepias incarnata) — Best choice for a rain garden or wet soil, but also thrives in well-drained soil if watered regularly. Grows 3 to 5 feet tall and 3 to 4 feet wide. Flower colors include pale pink, white, crimson and purple. Hardy in Zones 3-8.
- Common milkweed (Asclepias syriaca) — Plant this only if you have lots of space for it to spread. Plants spread by seeds and also by roaming roots that sprout to form new plants. Can be aggressive in a garden setting. Grows 2 to 5 feet tall and 2 to 3 feet wide. Hardy in Zones 3-9.
- Whorled milkweed (Asclepias verticillata) — White flowers top stems from mid to late summer. This is the milkweed to plant if your soil is so rough and rocky that no other milkweeds will grow. Grows to 2 feet tall and wide. Hardy in Zones 3-9.
- Tropical milkweed (Asclepias curassavica) — Also known as Mexican butterfly weed. Flowers feature several colors, including red, orange and gold. This is a non-native milkweed. It's a source of controversy because it grows year-round in the warmest regions and interrupts the normal migration patterns of monarch butterflies. In warmest zones, monarch experts suggest cutting tropical milkweed in fall and winter to 6 inches tall to encourage monarch butterflies to migrate. This milkweed also can infect monarchs with a harmful microorganism. Learn more about tropical milkweed and its impact on monarch butterflies at Monarch Joint Venture. Grows 2 to 3 feet tall and 1 to 3 feet wide. Hardy in Zones 9-11.
Using Milkweed in the Landscape
Milkweed blends beautifully with a host of planting partners. Bright orange or gold butterfly weed flowers are gorgeous planted with purple or blue perennials, such as asters, balloon flower or meadow sage. They also look striking mingled with coneflower, bee balm, Joe-pye weed and coreopsis. Other perennials that pair well with milkweed plants include black-eyed Susan, prairie blazing star and goldenrod. Ornamental grasses, such as little bluestem, prairie dropseed or carex also look good with milkweed, providing terrific textural contrast with their thin, strappy leaves.
Butterfly weed and swamp milkweed are definite must-haves if you’re designing an earth-friendly, pollinator or butterfly garden. Milkweed plants also fit well into prairie landscapes and wildlife gardens. For a rain garden, plant swamp milkweed.
A Word of Warning
Milkweed earns its name from the milky sap it produces. The sap contains toxic alkaloid compounds that can cause eye and skin irritation in pets when ingested. Some people react to the compounds by developing a rash. If the sap gets on your hands and into your eyes (like when wiping a sweaty brow), you can develop eye irritation hours later. Eye irritation is not permanent but can require a doctor’s attention. Take precautions when working with milkweed plant by wearing gloves, long sleeves and pants. Always wash your hands after working with milkweed.
Make way for monarchs! These pretty, but endangered, butterflies migrate each fall to spend winter where frosts won’t find them. Read on to see where you can experience this incredible annual migration.