Pictured above: Longleaf milkweed (Asclepias longifolia) by Eleanor Dietrich. Click on terms for botanical definitions. View post as a PDF.
Longleaf milkweed flowers are born in axillary or terminal umbels. Each flower bears a five-lobed calyx and five-lobed corolla, both of which are whitish-green with purple tips. Calyx lobes are reflexed. Leaves are long (up to 6 inches), linear to narrowly lanceolate (up to 3/8-inch wide) and sessile. They have small hairs scantly distributed along margins, over the upper surface and along veins of the lower surface. Leaves may be oppositely or alternately arranged. Stems are slender, rigid and slightly pubescent. Seeds are born in erect, smooth follicles that measure 3½ inches or longer.
The genus Asclepias is named for Asclepius, the Greek god of healing. The species epithet longifolia literally translates to “long leaf,” hence the common name.
Like all members of the Asclepias genus, Longleaf milkweed is a larval host plant for Monarch and Queen butterflies. The plant contains a milky latex that is toxic to most animals, but Monarchs and Queens are adapted to feed on them despite the chemical defense. The flowers are an important nectar source for bees and wasps.
Family: Apocynaceae (Dogbane family)
Native range: Panhandle west of Jefferson County, western peninsula from Citrus south to Monroe and Miami-Dade counties, and eastern peninsula from Seminole north to Nassau counties
To see where natural populations of Longleaf milkweed have been vouchered, visit florida.plantatlas.usf.edu.
Hardiness: Zones 8A–10B
Soil: Moist to wet soils
Exposure: Full sun to minimal shade
Growth habit: Up to 28”
Garden tips: Longleaf milkweed plants are not commercially available. Visit a natural area to see them.
For more information on other Asclepias species, see these resources:
- Milkweed (from 20 Easy-to-Grow Wildflowers)
- Carolina milkweed (Asclepias cinerea)
- Largeflower milkweed (Asclepias connivens)
- Pinewoods milkweed (Asclepias humistrata)
- Swamp milkweed (Asclepias incarnata)
- Fewflower milkweed (Asclepias lanceolata)
- Savannah milkweed (Asclepias pedicellata)
- Butterly milkweed (Asclepias tuberosa)
- Whorled milkweed (Asclepias verticillata)
- Green antelopehorn (Asclepias viridis)