Asclepias verticillata

Asclepias verticillata
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 L.
Natural range of Asclepias verticillata from USDA NRCS Plants Database.

Common names: Whorled Milkweed

Description

In general, with the Asclepias genus, they are perennial herbs usually 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.

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.

Distribution

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

Ecology

Habitat

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. It can be found in bluestem prairie. It increases with spring burning. It is a warm-season grass. Can occur in areas with soil disturbance. 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 and in flatwoods.

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.

Phenology

It flowers and fruits from April to September. 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).

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).

References and notes

Robertson data. Dataset compiled at Pebble Hill Fire Plots from 2005 to 2015.

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.

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.

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.

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.

Florida State University Robert K. Godfrey Herbarium database. URL: http://herbarium.bio.fsu.edu. 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.