Asclepias nivea – Caribbean milkweed Asclepias oenotheroide – zizotes milkweed Asclepias perennis – aquatic milkweed Asclepias speciosa – showy milkweed Asclepias subulata – rush milkweed Asclepias syriaca – common milkweed Asclepias tuberosa – butterfly weed Asclepias variegata – white milkweed Asclepias verticillata – whorled milkweed Asclepias vestita – woolly milkweed Asclepias viridis – green antelopehorn milkweed Calotropis gigantea – crown flower Calotropis procera Cynanchum laeve – sand vine milkweed Sarcostemma clausa – white vine Asclepias curassavica, or tropical milkweed, is often planted as an ornamental in butterfly gardens. Year-round plantings in the USA are controversial and criticised, as they may be the cause of new overwintering sites along the U.S. Gulf Coast, leading to year-round breeding of monarchs. This is thought to adversely affect migration patterns, and to cause a dramatic buildup of the dangerous parasite, Ophryocystis elektroscirrha. New research also has shown that monarch larvae reared on tropical milkweed show reduced migratory development (reproductive diapause), and when migratory adults are exposed to tropical milkweed, it stimulates reproductive tissue growth. Adult food sources Although larvae eat only milkweed, adult monarchs feed on the nectar of many plants, including: Apocynum cannabinum – Indian hemp Asclepias spp. – milkweed Aster sp. – aster Cirsium sp. – thistle Daucus carota – wild carrot Dipsacus sylvestris – teasel Echinacea sp. – coneflower Erigeron canadensis – horseweed Eupatorium maculatum – spotted Joe-Pye weed Eupatorium perfoliatum – common boneset Hesperis matronalis – dame's rocket Liatris sp. – blazing stars Medicago sativa – alfalfa Solidago sp. – goldenrod Syringa vulgaris – lilac Trifolium pratense – red clover Vernonia altissima – tall ironweed Monarchs obtain moisture and minerals from damp soil and wet gravel, a behavior known as mud-puddling. The monarch has also been noticed puddling at an oil stain on pavement. Flight and migration In North America, monarchs migrate both north and south on an annual basis, in a long-distance journey that is fraught with risks. This is a multi-generational migration, with individual monarchs only making part of the full journey. The population east of the Rocky Mountains attempts to migrate to the sanctuaries of the Mariposa Monarca Biosphere Reserve in the Mexican state of Michoacán and parts of Florida. The western population tries to reach overwintering destinations in various coastal sites in central and southern California. The overwintered population of those east of the Rockies may reach as far north as Texas and Oklahoma during the