Grow Milkweed for Monarch Butterflies

Swamp Milkweed for Monarch Butterflies and Caterpillars

Asclepias incarnata: Swamp milkweed, Swamp silkweed, Rose milkweed, White Indian hemp

Asclepias incarnata also attracts buckeyes, bumblebees, eastern tiger swallowtails, fritillaries, hairstreaks, honey bees, hummingbird moths, hummingbirds, skippers, spicebush swallowtails, and more

  • Perennial: USDA hardiness zones 3a-8b (lows -39.9 °C or -39.8 °F)
  • Native to most of the Continental USA and Eastern Canada
  • Full sun to partial shade
  • Height: 4 to 6 feet
  • Spacing: 2 to 3 ft
  • Flowers: pink with highlights of vibrant purple
  • Long summer bloom period

swamp-milkweed

swamp-milkweed2

Culture

Easily grown in medium to wet soils in full sun. Surprisingly tolerant of average well-drained soils in cultivation even though the species is native to swamps and wet meadows. Plants have deep taproots and are best left undisturbed once established. Foliage is slow to emerge in spring.

Noteworthy Characteristics

Asclepias incarnata, commonly called swamp milkweed, is an erect, clump-forming, Missouri native plant which is commonly found in swamps, river bottomlands and wet meadows throughout the State. It typically grows 3-4′ tall (less frequently to 5′) on branching stems. Small, fragrant, pink to mauve flowers (1/4″ wide), each with five reflexed petals and an elevated central crown, appear in tight clusters (umbels) at the stem ends in summer. Flowers are uncommonly white. Narrow, lance-shaped, taper-pointed leaves are 3-6″ long. Stems exude a toxic milky sap when cut. Flowers are followed by attractive seed pods (to 4″ long) which split open when ripe releasing silky-haired seeds easily carried by the wind. Flowers are very attractive to butterflies as a nectar source. In addition, swamp milkweed is an important food source (albeit somewhat less important than upland species of Asclepias) for the larval stage of Monarch butterflies.

Genus name honours the Greek god Asklepios, god of medicine.

Common Milkweed

Height: 2.00 to 3.00 feet
Spread: 0.75 to 1.00 feet
Bloom Time: June to August
Bloom Description: Pink, mauve, white
Sun: Full sun

Easily grown in average, dry to medium, well-drained soils in full sun. Drought tolerant. Does well in poor, dryish soils. Easily grown from seed, and will self-seed in the landscape if seed pods are not removed prior to splitting open. Can spread somewhat rapidly by rhizomes. Often forms extensive colonies in the wild.

Noteworthy Characteristics

Common milkweed is a rough, weedy Missouri native perennial which commonly occurs in fields, open woods, waste areas, roadsides and along railroad tracks throughout the State (Steyermark). It typically grows 3-4′ (less frequently to 6′) tall on stout, upright stems with thick, broad-oblong, reddish-veined, light green leaves (to 8″ long). Domed, slightly drooping clusters (umbels) of fragrant, pinkish -purple flowers appear mostly in the upper leaf axils over a long bloom period from late spring well into summer. Stems and leaves exude a milky sap when cut or bruised. Flowers give way to prominent, warty seed pods (2-4″ long) which split open when ripe releasing their numerous silky-tailed seeds for dispersal by the wind. Seed pods are valued in dried flower arrangements. Flowers are a nectar source for many butterflies and leaves are a food source for monarch butterfly larvae (caterpillars).

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