This variable species is widespread across eastern and central states. Although sometimes described as rhizomatous, it has deeply branching tap-roots that form clonal patches (Stevens 1966, Lucansky & Clough 1986); most other Asclepias species in eastern states have simple caudices with little basal branching. Typical soils for tuberosa in Ky. have intermediate fertility, with remnants of former Quercus alba woodland often present along nearby fencerows (especially in the Eden Shale region). It is most common in old hayfields and rights-of-way on moderately dry (subxeric) soils with mowing once or twice each year. Deer generally avoid eating the plant, except for pods, but cattle tend to reduce the species (unlike A. viridis). Most Ky. plants appear at least transitional to the western var cordata Beck. [= var. interior (Woods) Shinners], which has leaves that are cordate to hastate (versus cuneate) and widest below the middle (versus above). But colls. that are closer to the more eastern var. tuberosa are also scattered widely over the state. These taxa may not be worth separating in Ky., but see Y to west and W to east; they have often been treated as subspecies. Woodson's research (culminating in 1964) indicated that distinction of these taxa became reduced due to migration and mixing along roadsides during the 20th Century. Leaf width also varies greatly across the range; in Ky. this is mostly 1-2 cm wide. Further west some plants have leaves only 4-7 mm wide (Y); a "pollinator plot" planted by USACE near Nolin Lake (HART) has plants of this type (R. Seymour, pers. comm.).