Table of Contents for Long-leaf Milkweed (Asclepias longifolia)
Long-leaf Milkweed (Asclepias longifolia) is a herbaceous perennial that is found in the mid-western and eastern United States and Canada, except for the northeast. This plant is a host to the Monarch butterfly (Danaus plexippus) and Queen butterfly (Danaus gilippus). It can grow from 1 to 2.5 feet tall and has flowers that are greenish-white with a purple tinge that bloom from April to July. It is hardy in zones 4-10 (across varieties).
Taxonomy and Naming of Long-leaf Milkweed (Asclepias longifolia)
Taxonomy
Long-leaf milkweed (Asclepias longifolia) was named and described by Andre Michaux, a French Botanist, in Flora Borealis in 1803. The species has kept this name since and is a member of the Dogbane Family (Apocynaceae).
Varieties
This milkweed has two varieties, var. hirtella and var. longifolia. They differ in that var. hirtella has over 30 flowers and scabrous leaves, and var. longifolia has less than 30 flowers and glabrous leaves (Weakley 2022).
Meaning of the Scientific and Common Names
Scientific Name
The genus name, Asclepias, is named for the Greek god of healing, Asklepios (Flora of Wisconsin). The species name, longifolia, is Latin for the long leaves of the plant.
Common Name and Alternative Names
The common name describes the linear leaves of this plant. Another common name, savanna milkweed, describes the habitat.
Physical Description of Long-leaf Milkweed (Asclepias longifolia)
Description
- Plant Type: This plant is a herbaceous perennial.
- Height: 1 to 2.5 feet
- Stem: color ranges from green to purple
- Leaves: The leaves are opposite, simple, entire, sessile to subsessile, and linear-lanceolate in shape. The leaves range in size from 2 to 7 inches in length and 0.1 to 0.4 inches in width (Woodson 1954).
- Flower color: greenish-white with a purple tinge.
- Blooming period: This plant blooms from April to July.
- Fruiting type and period: This plant has follicles that mature in the late summer and fall.
Range of Long-leaf Milkweed (Asclepias longifolia) in the United States and Canada
This milkweed species grows in the mid-western and eastern United States except for the northeast. It is considered to be rare in the states of Minnesota, Michigan, West Virginia, Virginia, North Carolina, and the province of Ontario. This species also ranges into Mexico (Martin 1894).
Habitat
This species grows in moist areas and wetlands such as bogs, swamps, wet flatwoods, and moist prairies that have full sun.
Hosted Insects
This species is a host for the Monarch Butterfly (Danaus plexippus) and the Queen Butterfly (Danaus gilippus).
Other Supported Wildlife
This species is a nectar source to other butterflies, skippers, bees, and wasps during the growing season.
Frequently Asked Questions about Long-leaf Milkweed (Asclepias longifolia)
Is this plant poisonous?
Like other milkweeds, it has cardiac glycosides (cardenolides) and is considered to be poisonous with ingestion.
Does this plant have any ethnobotanical uses?
The Native American Ethobotanical Database does not list this species in particular, but milkweeds in general have been used for a number of medicinal uses and foods.
How is this plant distinguished from other milkweeds?
Long-leaf Milkweed is most similar to green milkweed (Asclepias hirtella) and has been listed as a variety of longifolia in some treatments. Green milkweed has a spread pubescence on the pedicels while long-leaf milkweed has an appressed pubescence (Turner 2009). The leaves of green milkweed are also slightly scabrous, whereas the other is not (Weakley 2022).
Is this plant invasive?
This species can grow in places that have been disturbed, but there is nothing in the literature indicating that it is invasive.
Gardening with Long-leaf Milkweed (Asclepias longifolia)
Hardiness
This species is hardy in zones 4-10. Variety hirtella is hardy in zones 4-9, while var. longifolia is hardy in zones 8-10. If your garden is within these zones and you have the right growing conditions (soil, moisture and exposure), you may well be able to grow this plant. However, if planted outside of its range, the hosted species may not recognize the plant or be harmed by ingesting a different species with an unfamiliar chemical composition.
Optimal Conditions
This species grows best in places it can receive full sun. It grows best in moist to wet soils.
References
- Martin, Sesse’ and Jose’ Mariano Mozino. 1894. Flora Mexicana a Martino Sesse et Josepho Marianno Mocino exarata. Oficina Tipografica de la Secretaria de Fomento.
- Turner, B.L. 2009. Taxonomy of Asclepias hirtella and A. longifolia (Apocynaceae). Phytologia 2:308-311.
- Weakley, A.S., and the Southeastern Flora Team. 2022. Flora of the southeastern United States. University of North Carolina Herbarium, North Carolina Botanical Garden.
- Woodson, Robert E. 1954. The North American Species of Asclepias L. Annals of the Missouri Botanical Garden 41: 1-211.
