How to Grow and Care for Milkweed
About Milkweed
Milkweed (Asclepias syriaca) grows 3 to 5 feet tall and is hardy in USDA zones 4 to 9. It grows best in full sun to part sun with low water.
Although less-than-ideal for mixed borders or formal gardens, ‘Common Milkweed’ is a highly-beneficial plant to grow for its ability to attract pollinators, especially butterflies. Monarch butterflies rely on this plant as a vital food source at each stage of their development. Since ‘Common Milkweed’ tends to spread aggressively, it is best-suited for sunny naturalized areas or butterfly gardens. Spheres of scented blossoms in shades of green, pink, white, or purple emerge from the plant throughout the summer, followed by capsules containing interesting, silvery seeds. Historically, the silken floss from the seed was removed by Native Americans and used to spin thread, and due to their buoyant qualities, the seed fibers were stuffed into life vests for rescue missions during World War II. The seed floss continues to be harvested in present times for use as a downy filling for pillows and other bedding. Although ‘Common Milkweed’ is poisonous to humans and pets, the plant contains a molecule which is of value in the medical field for the treatment of heart disease. ‘Common Milkweed’ will grow to a height of 3-5 feet and a width of 8 inches, although the plant tends to spread aggressively. Hardy throughout USDA zones 4-9, ‘Common Milkweed’ is native to eastern North America.
When to Plant Milkweed
Sow milkweed seed outdoors in fall so it gets the winter chill it needs, or plant nursery plants in spring after the last frost.
How to Plant Milkweed
‘Common Milkweed’ demands a minimum of 6 hours of direct sunlight daily. This plant will tolerate a variety of soil types but requires excellent drainage. Due to its ability to spread from seeds and rhizomes, ‘Common Milkweed’ can be difficult to control. Seed pods burst open in early fall and may be planted about an inch deep into moist soil. The plant may be propagated, as well, by digging and removing a section of root to transplant.
Milkweed Care
‘Common Milkweed’ flourishes in a variety of soil types but will not tolerate shade. This plant requires a minimum of 6 hours of direct sunlight daily, and will quickly expand to fill in any garden space. ‘Common Milkweed’ is highly-adaptable to arid conditions, requiring water only during extremely dry periods, which makes it especially helpful in the fight to prevent soil erosion.
Fertilizing Milkweed
‘Common Milkweed’ does not require fertilizer. The application of chemicals in fertilizers can potentially harm butterflies.
Pruning Milkweed
‘Common Milkweed’ stalks should be pruned several inches from the ground in late fall in order to encourage monarch butterflies to migrate and to help eradicate any harmful parasites that may linger on the plant.
Milkweed Pests and Diseases
‘Common Milkweed’ is not affected by any serious pests or diseases.
Is Milkweed Toxic to Cats and Dogs?
Yes. The ASPCA lists milkweed as toxic to dogs, cats and horses. It contains cardiac glycosides that can cause serious illness. If you think a pet has eaten a toxic plant, call your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435.
Milkweed FAQs
Why is milkweed important for monarch butterflies?
Milkweed is the only food monarch caterpillars eat, so planting it directly supports the monarch population.
Does milkweed spread?
Common milkweed spreads by underground runners and can form large colonies. Butterfly weed and swamp milkweed stay in clumps.
Does milkweed seed need cold stratification?
Yes. Most milkweed seed germinates best after 30 days of cold, moist conditions, either from fall sowing or in the refrigerator.
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