Asclepias verticillata

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Asclepias verticillata
Asclepias verticillata Gil.jpg
Photo taken by Gil Nelson
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta - Flowering plants
Class: Magnoliopsida - Dicotyledons
Order: Gentianales
Family: Asclepiadaceae
Genus: Asclepias
Species: A. verticillata
Binomial name
Asclepias verticillata
ASCL VERT dist.jpg
Natural range of Asclepias verticillata from USDA NRCS Plants Database.

Common name: Whorled milkweed

Taxonomic notes

Asclepias is named for Asklepio, the Greek god of medicine and healing.[1] Verticillata is Latin for whorled.[2]


Species in the genus Asclepias are typically perennial herbs with a milky sap. The stems are erect, spreading or decumbent and usually are simple and often solitary. The leaves are opposite to subopposite, are sometimes whorled, and rarely alternate. The corolla lobes are reflexed and are rarely erect or spreading. The filaments are elaborate into five hood forming a corona around the gynosteguim. The corona horns are present in most species.[3]

Specifically, for A. verticillata, the stems are simple or there is branching in the upper third portion. Grows approximately 3-8 dm tall and is pubescent in lines. There are numerous leaves that are whorled or subverticillate, are linear, and grow to be 3-7 cm long and 1-2 mm wide. The leaves are pubescent or glabrate and usually revolute. There are 2-8 umbels coming from the upper nodes, they are 2.2-5 cm broad. The peduncle is 1.5-2.5 cm long. The corolla is greenish white in color. The lobes are 3.5-4.5 mm long and have rose-purple tint at the tip of the lobes. The corona is 3-5 mm in diameter. The acicular horns are exserted. The follicles are erect and are 4.5-8.5 cm long and 4-6 mm broad. Flowers June to September; September to October.[3]


It is found from Massachusetts, south to Texas, east to Florida, and west to Arizona.[4]



Native upland pine and pine-hardwood communities, loblolly pine plantations (Ultisols), borders of wetland depressions within pine communities, sandhills and sand ridges, (Entisols), open calcareous glades, bluffs along Apalachicola River,[5] and roadsides.[6] It can be found in bluestem prairie. It increases with spring burning. It is a warm-season grass.[7] Can occur in areas with soil disturbance.[5] Thrives in frequently burned areas and flowers within two months of burning in the growing season (Robertson observation). Tolerates full sunlight to partial shade. Tolerates moist to xeric conditions but seems to be limited to sandy or calcareous soil. Found barrens of thin soils of rock outcrops (mafic rocks), also in woodlands and sandhills.[4] and in flatwoods.[8]

Associated species include Pinus palustris, Quercus laevis, Q. margaretta, Q. rubra, Tragia, Setaria, Panicum, Hedyotis, Euphorbia floridana, Gaillardia aestivalis, Rhynchospora globularis, Pteridium aquilinum, Polianthes, Fraxinus, Melanthera nivea, sweetgum, poison oak, mockernut hickory, and others.[5]


It flowers and fruits from April to September.[5][4] It resprouts and flowers within a few weeks of being burned from early spring through summer, but it also flowers in years when it is not burned up to at least five years following fire, primarily in July and August in northern Florida and southern Georgia (KMR[9]). It is one of the last milkweed species to flower and is a common late season host plant for monarch larvae.[10]

Seed dispersal

Asclepias verticillata has seed pods that extend vertically from meristems near the top of the stem. Seeds are dispersed by wind after pod dehiscence. Seeds are up to 4 mm in diameter but have a large white coma facilitating distant seed dispersal (KMR[11]). This species is thought to be dispersed by wind.[12]

Fire ecology

It has been observed in recently burned mesic Pinus densa (rockland pine) communities of Hendry County, FL.[13]


Pollination of Asclepias is unusual. Pollen is contained in sacs (pollinia) located in the slits of the flower (stigmatic slits), when a pollinator walks across the flower head, these sacs attach to the pollinator and disperses on to another plant when the pollinator lands and walks.[1] There is no specialist insect pollinator[14] Pollinated by Monarch butterflies.

The following species have been observed pollinating A. verticillata: honeybees, bumblebees, Halictid bees (Halictus spp., Lasioglossum spp.), Halictid cuckoo bees (Sphecodes spp.), sand-loving wasps (Tachytes spp.), weevil wasps (Cerceris spp.), Sphecid wasps (Sphex spp., Prionyx spp.), Five-banded Tiphiid Wasp (Myzinum quinquecinctum), Northern Paper Wasp (Polites fuscatus), spider wasps (Anoplius spp.), Eumenine wasps (Euodynerus spp., etc.), Syrphid flies, thick-headed flies (Physocephala spp., etc.), Tachinid flies, flesh flies (Sarcophagidae), Muscid flies, Painted Lady (Vanessa cardui) and other butterflies, Peck's Skipper (Polites peckius) and other skippers, Squash Vine Borer Moth (Melittia cucurbitae) and other moths, and Pennsylvania Soldier Beetle (Chauliognathus pennsylvanicus).[15]

Use by animals

It is highly toxic to livestock and horses.[2]

Insects that destructively feed on the foliage, flowers and seedpods include: Small Milkweed Bug (Lygaeus kalmii), Milkweed Leaf Beetle (Labidomera clivicollis), Yellow Milkweed Aphid (Aphis nerii), and a moth, the Delicate Cycnia (Cycnia tenera).[15]

Conservation and management

Cultivation and restoration

Photo Gallery

References and notes

  1. 1.0 1.1 [[1]]Florida Native Plant Society. Accessed: March 30, 2016
  2. 2.0 2.1 [[2]]North Creek Nurseries. Accessed: March 31, 2016
  3. 3.0 3.1 Radford, Albert E., Harry E. Ahles, and C. Ritchie Bell. Manual of the Vascular Flora of the Carolinas. 1964, 1968. The University of North Carolina Press. 848-850. Print.
  4. 4.0 4.1 4.2 Weakley, Alan S. Flora of the Southern and Mid-Atlantic States: Working Draft of 21 May 2015. University of North Carolina Herbarium (NCU). PDF. 933.
  5. 5.0 5.1 5.2 5.3 Florida State University Robert K. Godfrey Herbarium database. URL: Last accessed: July 2015. Collectors: Loran C. Anderson, Guy Anglin, Gary R. Knight, John B. Nelson, Robert L. Lazor, Robert K. Godfrey, R. Kral, R. R. Smith, T. Myint, N. C. Henderson, S. W. Leonard, Cecil R Slaughter, Jimmy Meeks, Brenda Herring, Don Herring, William Lindsey, S.C. Hood, Richard S. Mitchell, Kevin Oakes, Tom Hyde, R.A. Norris, Andre F. Clewell, R. Komarek, R. F. Doren, Chris Cooksey, M. Davis, MacClendons, G. Wilder. States and Counties: Florida: Leon, Lee, Walton, Washington , Okaloosa, Jackson, Gadsden, Jefferson, Pasco, Liberty, Taylor, Marion, Charlotte, Wakulla, Suwannee, Orange, Levy, Citrus, Escambia, Dixie, Georiga: Thomas. Compiled by Tall Timbers Research Station and Land Conservancy.
  6. Observation by Floyd Griffith near Ponce DeLeon Springs State Park, FL, August 23, 2015, posted to Florida Flora and Ecosystematics Facebook Group August 23, 2015.
  7. Hover, E. I. and T. B. Bragg (1981). "Effect of season of burning and mowing on an eastern Nebraska Stipa-Andropogon prairie." American Midland Naturalist 105: 13-18.
  8. Wunderlin, Richard P. and Bruce F. Hansen. Guide to the Vascular Plants of Florida. Third edition. 2011. University Press of Florida: Gainesville/Tallahassee/Tampa/Boca Raton/Pensacola/Orlando/Miami/Jacksonville/Ft. Myers. 271. Print.
  9. KMR observations at Pebble Hill Plantation Fire Plots near Thomasville, GA.
  10. [[3]]Monarch Watch. Accessed: March 31, 2016
  11. Observations at Pebble Hill Plantation near Thomsville, Georgia
  12. Kirkman, L. Katherine. Unpublished database of seed dispersal mode of plants found in Coastal Plain longleaf pine-grasslands of the Jones Ecological Research Center, Georgia.
  13. Observation posted to Florida Flora and Ecosystematics Facebook Group.
  14. [[4]]Xerces Society. Accessed: March 30, 2016
  15. 15.0 15.1 [[5]]Illinois Wildflowers. Accessed: March 31, 2016