What is Milkweed?
{{taxobox |name = Milkweeds |image = Purple Milkweed Asclepias purpurascens Feeding Ant.jpg |image_caption = ''Asclepias'' + ant feeding on nectar |regnum = [[Plantae]] |unranked_divisio = [[Angiosperms]] |unranked_classis = [[Eudicots]] |unranked_ordo = [[Asterids]] |ordo = [[Gentianales]] |familia = [[Apocynaceae]] |subfamilia = [[Asclepiadoideae]] |genus = '''''Asclepias''''' |genus_authority = [[Carolus Linnaeus|L.]] |subdivision_ranks = Species |subdivision = See text. |}} The '''milkweeds''', '''''Asclepias''''' ([[Carolus Linnaeus|L.]] 1753), are a [[genus]] of herbaceous [[perennial plant|perennial]], [[dicotyledon]]ous [[plant]]s that contains over 140 known species. Milkweeds are an important nectar source for [[bee]]s and other nectar eaters, and a food source for [[caterpillar]]s. The weeds are eaten by caterpillars of the [[Monarch (butterfly)|monarch butterfly]] and its relatives, and by other herbivorous insects (such as [[beetle]]s, and [[true bug]]s). These insects are able to feed on the plants despite their chemical defences. Milkweed is named after its milky [[sap]], which contains [[alkaloid]]s, [[latex]], and several other complex compounds. Some species are [[toxic]]. [[Pollination]] in this genus is accomplished in an unusual manner, as the [[pollen]] is grouped into pollen sacs. The feet or mouthparts of flower visiting insects such as [[bees]], [[wasp]]s and [[butterflies]], slip into one of the five slits in each flower formed by adjacent [[anther]]s. The bases of the pollinia then mechanically attach to the insect, pulling a pair of pollen sacs free when the pollinator flies off. Pollination is effected by the reverse procedure in which one of the pollinia becomes trapped within the anther slit. Milkweeds have three [[Defence against herbivory|defenses]] to limit damage by [[caterpillar]]s and other insects: hairs on the leaves, toxins, and [[latex]] fluids. Some more recent milkweed species grow faster than older species. They have the potential to grow faster than caterpillars