Usually vigorous perennials, with very curious and ornamental flowers, common in fields and on river banks in North America and Canada, where they sometimes become troublesome weeds. Of the species in cultivation, A. Cornuti and A. Douglasi could be naturalised easily in rich deep soil in wild places. The showy and dwarfer Asclepias tuberosa requires very warm sand soils to flower as well as in its own dry hills and fields. A good many of the hardy species are not introduced ; for such the place is the wild garden. Some of them are water-side plants, such as A. incarnata, the Swamp Silkweed of the United State-.