Asclepias meadii

"Asclepias meadii has a single slender unbranched stalk, 8 to 16 inches high, without hairs but with a whitish waxy covering. The hairless leaves are opposite, broadly ovate, 2 to 3 inches long, 3/8 to 2 inches wide, also with a whitish waxy covering. A solitary umbel at the top of the stalk has 6 to 15 greenish, cream-colored flowers." (USFWS 2005).

Stem to 2 ft, smooth, containing milky sap. Leaves opposite, simple, narrowly to broadly lance-shaped, toothless, without stalks. Flowers borne in solitary drooping umbel at end of a long stalk. Corolla greenish white, hoods purple or greenish purple. Flowers open in late May and early June.

Asclepias meadii is a species of dry-mesic to mesic tallgrass prairies or glade/barren habitat characterized by vegetation adapted for drought and fire (Chaplin et al. 1990; Barbour and Billings 1988, Axelrod 1985; USFWS 2005, 2012). The species has been recorded from chert glades (Steyermark 1977) and sandstone rock-ledges (Voigt and Mohlenbrock 1964). Plants seem to prefer full sun, occupying slopes that grade between 0 and 18% (Chaplin et al. 1990).

Associates include a lengthy list of over 60 prairie plants (Betz 1989). Among the associates are Achillea millefolium, Amorpha canescens, Andropogon gerardii, A. scoparius, Antennaria neglecta, Asclepias viridis, A. tuberosa, Baptisia bracteata, Coreopsis palmata, Dalea candida, D. purpurea, Desmanthus illinoensis, Dichanthelium oligosanthes, Echinacea pallida, Erigeron strigosus, Eryngium yuccifolium, Liatris pycnostachya, Lithospermum canescens, Lobelia spicata, Phlox pilosa, Polytaenia nuttallii, Psoralea tenuiflora, Ratibida pinnata, Scleria triglomerata, Silphium laciniatum, Sisyrinchium campestre, Sorghastrum nutans, Sporobolus heterolepis, Tripsicum dactyloides, and Viola pedatifida (Chaplin et al. 1990, Betz 1989).

In eastern Kansas, populations occur predominantly on the unglaciated terrain of the Kansas River (Chaplin et al. 1990). The majority of known sites are on limestone bedrock, with two exceptions occurring over sandstone (McGregor 1987). These sites are typically well-drained to excessively drained with silty-loam mollisol soils derived from loess residuum, limestone, shale, glacial till or sandstone (Freeman 1988). Populations typically occur in upland tallgrass prairie sites. At such sites, associates frequently include the western prairie fringed orchid and the prairie mole-cricket (Gryllitalpa major) (Busby 1990, Figg and Calvert 1987). A small population was discovered on a sandstone prairie which was invaded heavily by Quercus marilandica, Q. stellata, and Juniperus virginiana (Chaplin et al. 1990).

In Illinois, populations of A. meadii occur in tallgrass prairie and dry barrens (Kurz and Bowles 1981). Populations occur in southern Illinois in the unglaciated Shawnee Hill Division (Mohlenbrock 1986). It is also known from the glaciated portion of east-central Illinois known as the Grand Prairie Division (Mohlenbrock 1986). In the sand barrens of Illinois, trees associated with A. meadii include Quercus marilandica, Q. stellata, Q. velutina, and Juniperus virginiana. Other associated prairie species include: Allium canadense, Anemone cylindrica, Apocynum sibiricum, Aster ericoides, Aster laevis, Cirsium discolor, Convolvulus sepium, Fragaria virginiana, Helianthus maximilliana, Lithospermum canescens, Petalostemum purpureum, Poa compressa, Polygala senega, Sisyrinchium albidum, Solidago rigida, Sporobolus heterolepis, and Stipa spartea (Swink 1974, Litzow 1978, Kurz and Bowles 1981).

Steyermark (1977) stated that A. meadii was rare and local in the southern half of Missouri, occurring in dry upland prairies and chert-lime glades. Currently, it is uncommon in western Missouri, mostly in the Unglaciated Plains Division, in upland prairies and igneous glades (Yatskievych 2006). Most populations are on mollisols and alfisols which formed over loess, glacial till, limestone, sandstone and shale (Morgan 1980).

In Iowa, A. meadii is restricted to the Southern Iowa Drift Plain (Prior 1976). Extant populations occur on clay-loam and silty clay-loam mollisols developed from weathered Kansas age drift covered with a moderate to thick layer of loess (Freeman 1988).

A single historic record of A. meadii exists from Indiana, collected near Crown Point on dry ground in 1888 (IN NHP). Similarly, there is one 1879 record from Lancaster in Wisconsin (WI NHP).

Asclepias meadii is a polycarpic perennial (Chaplin et al. 1990). Plants appear to be long-lived and may live for more than a century (Betz and Hohn 1978).

Mead's milkweed reproduces sexually through seed production and vegetatively through spreading rhizomes (Chaplin et al. 1990). Sexual reproduction in A. meadii is apparently rare (Kurz and Bowles 1981), due to a number of factors. In addition to low fruit set, seed viability within A. meadii fruits is typically low and may attribute significantly to the low fruit production found in extant populations (Betz 1988).

Although asexual reproduction is known in A. meadii, little specific information has been accumulated with regards to specific means. The number of rhizomes produced per genet and the extent to which they spread is unknown (Chaplin et al. 1990). The rhizomatous nature of the species has likely sustained it in habitats where mowing (and the subsequent removal of seeds) was a frequent regime (Freeman 1988).

Pollen is shed by pollinaria (Bookman 1981) which are disseminated by insects (Chapman et al. 1990). Relatively few insects have been observed on A. meadii plants, however (Betz 1989).

A two-week difference in flowering time between plants in the south (southern Kansas and Missouri) and the north (northern Illinois) has been noted (Schwegman 1988, Betz 1967). In southern Illinois, A. meadii emerges between April 11-23 and demonstrates slow growth until about 6 cm tall. Between May 15 and June 3 there is rapid stem elongation until mature height (about 0.6 m). Flowering frequently occurs between May 21 and June 18. Single fruits develop from each inflorescence, the follicles or pods observable by late June. By late August the pods have elongated to their maximum size (4 to 8 cm) and are greenish in color. These darken as the fruits mature and dehisce in mid-September to mid-October to release the numerous, hairy seeds. The plants begin to wither with first frosts, and are no longer visible by early November (Biotic Consultants 1976).

Asclepias meadii is self incompatible (Tecic et al. 1998). A. meadii may take 15 years or more to mature from a germinating seed to a flowering plant (USFWS 2005). Observations show that individual plants produce flowers for two or three years and then rest, and in some cases completely disappear for a few years (Harrison, 1987). The low number of individual plants at any one site may not attract potential pollinators, and this may be a cause for low reproductive success (Betz 1989). A. meadii also spreads vegetatively through rhizomes (USFWS 2005).

Asclepias meadii flowers as early as late May in the south through mid to late June in the north (USFWS 2005). Young green fruit pods appear by late June and reach their maximum length of 1.5 to 4 inches by late August or early September (USFWS 2005). The hairy seeds within these pods mature by mid-October (USFWS 2005).

A serious problem is removal of immature fruits/seeds by haying, thus precluding recruitment of new individuals. Studies by Tecic et al. (1998) and Bowles et al. (1998) showed that sites that were annually mowed had largely clonal, genetically depauperate populations of Asclepias meadii. In contrast, sites that were burned but not mowed had much greater genetic variation (Bowles et al. 1998; Tecic et al. 1998; Yatskievych 2006).