AMES, Iowa – Some milkweed species are attractive additions to home landscapes, and monarch butterflies like them too. Here are some tips from Iowa State University Extension and Outreach horticulturists on selecting and establishing milkweed. For more information, contact the ISU Hortline at 515-294-3108 or firstname.lastname@example.org.
Which milkweed species are best suited to home landscapes?
Common milkweed (Asclepias syriaca) tends to be too vigorous and weedy for beds and borders. However, butterfly weed (Asclepias tuberosa) and swamp milkweed (Asclepias incarnata) are non-aggressive, attractive additions to home landscapes.
Butterfly weed is a native Iowa perennial. It is typically found in prairie remnants and roadsides throughout the state. Butterfly weed has narrow, lance-shaped leaves, grows 2 to 3 feet tall, and flowers from June to September. The flowers are usually bright orange, but are occasionally yellow. Because of a specialized pollinating mechanism, only a few pods develop on most plants. The pods are spindle-shaped, 3 to 5 inches long and contain numerous silky-tailed seeds. Butterfly weed has a deep taproot. The stems of butterfly weed produce a watery, translucent sap when cut, rather than a milky sap common to most milkweeds.
Butterfly weed is an excellent plant for perennial beds and borders. It is easy to grow, requires very little maintenance, and has few pest problems. Plants possess excellent heat and drought tolerance. Butterfly weed requires full sun and a well-drained soil. It performs well in dry soils and poor, infertile soils.
A limited number of butterfly weed cultivars are available. ‘Gay Butterflies’ has flowers in shades of red, orange or yellow. ‘Hello Yellow’ has bright, yellow flowers.
Swamp milkweed (also known as rose milkweed) is another native perennial. It typically is found in prairie potholes, at the edges of marshes and in wet ditches. Swamp milkweed has 3- to 6-inch-long, lance-shaped leaves, grows 3 to 4 feet tall and blooms from July through August. The vanilla-scented flowers are pale pink to rose-purple. The flowers are followed by 3- to 4-inch pods that contain numerous plumed seeds. Stems and leaves exude a milky sap when cut or bruised.
Swamp milkweed is an excellent perennial for low sites or other moist locations in the landscape. Plants tolerate short dry periods, but prefer soils that are consistently moist or wet. Swamp milkweed requires full sun.
A small number of cultivars are available. The individual flowers of ‘Cinderella’ have pink to dark pink, reflexed petals and pink to white crowns. ‘Ice Ballet’ is a white-flowering cultivar. ‘Soulmate’ has deep rose-pink flowers.
How can I establish butterfly weed and swamp milkweed in the home landscape?
Butterfly weed and swamp milkweed can be established by sowing seeds. They also can be established by planting bare-root or potted plants. Growing plants from seeds is rather challenging. The successful establishment of both milkweed species is much easier with the planting of bare-root or potted plants. Seeds and bare-root plants are available from mail-order nurseries that specialize in native plant materials. Potted plants are available at local garden centers and nurseries.
Is it possible to transplant butterfly weed or swamp milkweed?
Butterfly weed and swamp milkweed have deep taproots. As a result, both plants are difficult to transplant once established in the landscape. When planting butterfly weed and swamp milkweed, choose their planting sites carefully and do not disturb them after planting.
Are butterfly weed and swamp milkweed suitable hosts for monarch butterflies?
Monarch butterfly larvae feed on the foliage of butterfly weed, swamp milkweed and most other milkweed species.
Photo credit: johnsroad7/stock.adobe.com