Asclepias syriaca (Common Milkweed)

Asclepias syriaca, commonly known as Common Milkweed, is a robust perennial native to North America. As one of the most well-known milkweed species, it plays a critical role in supporting monarch butterflies and other pollinators. This plant thrives in meadows, roadsides, and open fields, where it spreads readily through underground rhizomes, forming dense colonies. Its fragrant, globe-shaped flower clusters and broad leaves make it an excellent choice for wildlife-friendly gardens.

Milkweed plants belong to the Apocynaceae family, which includes other flowering plants such as oleander, hoya, plumeria, and the desert rose.

Description

Common Milkweed is a hardy, rhizomatous perennial known for its domed clusters of fragrant, pinkish-purple, star-shaped flowers that bloom from early to late summer. A magnet for butterflies and bees, its nectar-rich blooms appear in the upper leaf axils of sturdy, upright stems. Thick, oval-shaped green leaves with striking red veins add to its appeal. In fall, prominent seed pods split open, releasing silky-haired seeds. Easy to grow, this fast-spreading milkweed thrives in gardens and natural settings.

Native Habitat

Common Milkweed is widely distributed across North America, from Canada to the eastern and central United States. It thrives in prairies, fields, roadsides, and disturbed areas, where it naturally regenerates and spreads.

Unlike Swamp Milkweed (Asclepias incarnata), which prefers moist environments, Common Milkweed tolerates drier, sandy, and rocky soils, making it highly adaptable.

Plant Type and Habit

• Plant Type:  Rhizomatous perennial
• Growth Habit: Upright, spreading via rhizomes
• Lifespan: Long-lived perennial
• Root System: Deep, extensive rhizomes—once established, this milkweed spreads aggressively.

Size

Spreads aggressively through rhizomes, forming extensive colonies. May also self-seed if seed pods are not removed before they split open and release seeds. Its vigorous growth can make it challenging to control, so it’s best planted in areas where its spreading nature is welcome.

• Height: 3-5 feet (90-150 cm)
• Spread: 8-12 inches (20-30 cm)

Flowers and Fruits

• Flower Color: Dusty pink to lavender

• Bloom Time: Long-lasting bloom period from early to late summer

• Fragrance: Very strongly and sweetly scented

• Flower Shape: Large, 2- to 3-inch domed umbels of five-petaled flowers. Each cluster holds up to 100 star-like blooms, typically forming 1-3 clusters per stem. Flowers emerge from the leaf axils and often droop gracefully, adding to their delicate charm.

After flowering, Common Milkweed produces large, warty seed pods, which open in fall to winter, releasing wind-dispersed seeds with silky filaments.

Foliage

The foliage serves as a larval host for monarch butterfly caterpillars, which feed exclusively on milkweed species.

• Leaf Shape: Thick, oblong, opposite. The leaf tips are either rounded at both ends or abruptly pointed.
• Leaf Size: 3-12 inches long (7-30 cm)
• Leaf Color: Light green with a soft, downy underside and prominent reddish veins.

Hardiness

Common Milkweed is hardy in USDA zones 3-9 and thrives in a wide range of climates. It is highly cold-hardy, tolerating frost and snow while also being drought-resistant once established.

Uses in the Garden

Ornamental Uses:

• Adds vertical interest to meadows, prairies, and native plant gardens
• Works well in pollinator gardens and butterfly habitats
• Ideal for dried flower arrangements, thanks to its unique seed pods

Ecological Uses:

• Milkweed plants are essential for monarch butterfly survival, providing the sole host for their larvae. Over the past 20 years, North America’s monarch population has declined by 90%, making milkweed conservation more critical than ever. By planting milkweed in your own garden, you can help reverse the fortune of these beautiful insects!
• Helps prevent soil erosion and contributes to meadow restoration projects.

Native Americans used milkweed fibers for textiles and cordage. During WWII, its seed coma was harvested for life jacket stuffing. Today, it’s used in pillows and blankets.

Wildlife Value

Common Milkweed is a powerhouse for wildlife, offering both habitat and food for various species. Monarch butterfly caterpillars rely on its leaves as a primary food source, while adult monarchs and other butterflies feast on its nectar-rich flowers. Native bees are frequent visitors, benefiting from the plant’s abundant nectar supply. This plant also attracts over 450 insects, which are known to feed on some portion of the plant.

Discover more plants that attract butterflies.

Toxicity

Common Milkweed has low toxicity but contains cardiac glycosides and resinoids, which can cause nausea, vomiting, diarrhea, weakness, and confusion if ingested in large amounts. Its milky sap may cause contact dermatitis and eye irritation. Toxic parts include flowers, fruits, leaves, roots, seeds, and stems. Harmful to humans, cats, dogs, and horses.

Monarch butterfly caterpillars store these toxins in their bodies, making them unpalatable to predators.

Deer and Rabbits

Common Milkweed is naturally resistant to deer due to its milky sap, which contains toxic cardiac glycosides.

Invasiveness

Common Milkweed spreads aggressively through deep rhizomes and self-seeding. While beneficial in naturalized landscapes, it can quickly take over small gardens. To control its spread, remove seed pods before they open.

Why Grow Common Milkweed?

Common Milkweed is a must-have for pollinator gardens. With its fragrant blooms, essential role in monarch conservation, and easy-growing nature, it offers both beauty and ecological benefits. Whether planted in meadows, prairies, or roadside habitats, this resilient wildflower is a vital component of native ecosystems.

Milkweed: Is it Right for Your Garden? Pros and Cons Explained

How to Grow and Care for Common Milkweed

Light

• Prefers full sun for optimal flowering

Soil

• Thrives in well-drained, sandy, or loamy soil. Tolerates poor, dry, or rocky soils. Does not tolerate wet conditions.

Watering

• Requires moderate watering in the first year for strong root development. Drought-tolerant once established

Fertilization

• Generally low-maintenance, but a light application of compost in spring can promote growth

Pruning

• Cut back in late fall to remove spent stems. Deadheading can help control self-seeding

Overwintering

• No special care is needed—Common Milkweed is cold-hardy and returns each year.

How to Propagate Common Milkweed

From Seeds

Common Milkweed seeds require cold stratification to break dormancy.

• Store seeds in moist vermiculite at 35–38°F (1.5–3.3°C) for 30 days
• Direct sow seeds in fall or early spring
• Keep soil moist until germination, which occurs in 2-4 weeks

From Root Cuttings

• In late fall or early spring, dig up a mature plant
• Cut 4-inch (10 cm) sections of the rhizome
• Replant in moist, well-drained soil and keep consistently watered

Common Problems and Pests

Common Milkweed is generally pest-resistant, but it may attract aphids. These can be left alone, as they attract beneficial insects like ladybugs and lacewings, which keep their populations in check.

Got questions about milkweed? We have the answers!