Asclepias viridis

Asclepias viridis

Apparently Secure (NatureServe)[1]
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Gentianales
Family: Apocynaceae
Genus: Asclepias
Species:
A. viridis
Binomial name
Asclepias viridis

Asclepias viridis is a species of milkweed, a plant in the dogbane family known by the common names green milkweed, green antelopehorn and spider milkweed.[1][2][3][4] The Latin word viridis means green. The plant is native to the midwestern, south central and southeastern United States, as well as to the southeastern portion of the western United States.[1]

A. viridis is a perennial forb with alternately arranged leaves. The inflorescence is an umbel of white flowers with purplish centers.[2] Its root system is a taproot,[5] like that of butterfly weed (A. tuberosa).

A. viridis grows on many types of soil. It is common in overgrazed pasture land and roadsides.[2]

Ecology

Like some other milkweed species, A. viridis is a host plant for the monarch butterfly (Danaus plexippus).[6] It is one of the most important host plants in the southern United States for the generation of monarch butterflies that develop from eggs that monarchs have laid after spending the winter in Mexico.[7]

Monarch Watch provides information on rearing monarchs and their host plants.[8] Efforts to restore falling monarch butterfly populations by establishing butterfly gardens and monarch migratory "waystations" require particular attention to the target species' food preferences and population cycles, as well to the conditions needed to propagate and maintain their food plants.[9]

For example, where it grows in the southern Great Plains and in the western United States, monarchs reproduce on A. viridis, especially when its foliage is soft and fresh. Because monarch reproduction peaks in those areas in late summer and early fall when scenescent milkweed foliage is old and tough, A. viridis needs to be mowed or cut back in July to assure that it will be regrowing rapidly when monarch reproduction reaches its peak.[10]

A. viridis is one of the first milkweeds to bloom in the Ohio River Valley (May to June). In that area, monarch butterfly and milkweed tussock moth (Euchaetes egle) caterpillars are seldom found on the plant as it sheds its leaves and becomes dormant in late June to early July before the two Lepidoptera species arrive.[3] However, in Texas, A. viridis is dormant by July and then re-sprouts in the fall during some years, while in other years, it stays green all summer and blooms a second or third time.[11]

Cultivation

The plant is difficult to cultivate and does not grow well in containers.[12] The seeds of some milkweeds need periods of cold treatment (cold stratification) before they will germinate.[13] To protect seeds from washing away during heavy rains and from seed–eating birds, one can cover the seeds with a light fabric or with an 0.5 in (13 mm) layer of straw mulch.[14] However, mulch acts as an insulator. Thicker layers of mulch can prevent seeds from germinating if they prevent soil temperatures from rising enough when winter ends. Further, few seedlings can push through a thick layer of mulch.[15]

References

  1. ^ a b c "Asclepias viridis: Spider Milkweed". NatureServe Explorer. Arlington, Virginia: NatureServe. January 30, 2026. Retrieved February 9, 2026.
  2. ^ a b c Davis, Lee (May 31, 2006). "Plant guide for Green Milkweed: Asclepias viridis Walt" (PDF). Washington, D.C.: United States Department of Agriculture: Natural Resources Conservation Service. Archived (PDF) from the original on July 11, 2021. Retrieved July 11, 2021.
  3. ^ a b Taylor, David. "Green Antelopehorn (Asclepias viridis)". Plant of the Week. Washington, D.C.: United States Department of Agriculture: United States Forest Service. Archived from the original on March 27, 2021. Retrieved July 11, 2021.
  4. ^ Borders, Brianna; Casey, Allen; Row, John M.; Wynia, Rich; King, Randy; Jacobs, Alayna; Taylor, Chip; Mader, Eric (June 2013). "Asclepias viridis Green antelopehorn". In Walls, Hailey; Rich, Kaitlyn (eds.). Pollinator Plants of the Central United States: Native Milkweeds (Asclepias spp.) (PDF). Portland, Oregon: The Xerces Society for Invertebrate Conservation. p. 13. Archived (PDF) from the original on November 6, 2020. Retrieved February 6, 2026.
  5. ^ "Asclepias viridis Walter: Green Milkweed". Lady Bird Johnson Wildflower Center. Austin, Texas: University of Texas at Austin. Archived from the original on November 12, 2025. Retrieved February 6, 2026.
  6. ^ Van Hook, Tonia; Zalucki, Myron P. (1991). "Oviposition by Danaus plexippus (Nymphaidaie: Danainae) on Asclepias viridis in Northern Florida" (PDF). Journal of the Lepidopterists' Society. 45 (3). The Lepidopterists' Society: 215–221. Archived (PDF) from the original on August 12, 2025. Retrieved February 9, 2026 – via Peabody Museum of Natural History at Yale University.
  7. ^ Multiple sources:
  8. ^ "Monarch Watch". monarchwatch.org. Retrieved September 27, 2015.
  9. ^ Multiple sources:
  10. ^ National Academies of Sciences, Engineering, and Medicine (2020). Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies. Washington, D.C.: National Academies Press. pp. 79–80. doi:10.17226/25693. ISBN 9780309481328. LCCN 2020935714. OCLC 1229163481. S2CID 218854539. National Cooperative Highway Research Program (NCHRP) Research Report 942. Archived from the original on July 29, 2020. Retrieved July 8, 2021. Could roadside mowing stimulate milkweed growth and support monarch breeding? Limited research in eastern North America has shown that spring or summer mowing can promote new growth and extend the availability of milkweed plants for monarch breeding. Mowing may stimulate growth of some milkweed species, particularly those that spread through rhizomes like common milkweed (A. syriaca) and showy milkweed (A. speciosa). Summer (June or July) mowing in Michigan resulted in more monarch eggs on regenerated stems than unmowed stems. Summer (July) mowing and burning can increase green antelopehorn milkweed (A. viridis) availability in the late summer and early fall in the Southern Great Plains, whereas in areas without mowing, the milkweed has senesced by August. In the West, showy milkweed will regrow after summer mowing and continue to support monarch breeding (Stephanie McKnight, personal observation). However, more research is needed in other areas to determine the optimal timing and frequency of mowing that promotes not only milkweed but also nectar plants. It is also unknown if the benefit of additional milkweed availability in the fall outweighs the costs of the larval mortality caused by summer mowing. The benefits are likely greater in areas that primarily have breeding monarchs in the spring and fall and where the dominant species of milkweed spread by rhizomes. Sources: Alcock et al. 2016; Baum and Mueller, 2015; Bhowick 1994; Haan and Landis 2019; Fischer et al. 2015
  11. ^ "Green Milkweed, Asclepias viridis". Carol's World. Carol Clark. April 19, 2020. Archived from the original on January 13, 2025. Retrieved February 9, 2026.
  12. ^ Maeckle, Monika (March 13, 2013). "Persnickety Texas Milkweeds "May not Lend Themselves to Mass Seed Production"". Texas Butterfly Ranch. Archived from the original on November 14, 2025. Retrieved February 7, 2026.
  13. ^ Multiple sources:
  14. ^ Multiple sources:
  15. ^ Bush-Brown, James; Bush-Brown, Louise (1958). "Chapter 32: Mulches". America's garden book. New York: Charles Scribner's Sons. p. 768. LCCN 58005738. OCLC 597041748 – via Internet Archive.
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