Asclepias Syriaca

Common Milkweed

Common Milkweed is an important plant because so many species of insects depend on it. Monarch Caterpillars, milkweed bugs, and milkweed leaf beetles only eat milkweed and their populations are declining because milkweeds are being eliminated by the use of herbicides farming and human development. Efforts to increase monarch butterfly populations by establishing butterfly gardens require particular attention to the butterfly's food preferences and population cycles, as well to the conditions needed to propagate milkweed. For example in the northeastern United States, monarchs prefer to reproduce on Asclepias syriaca, especially on young, soft leaves. Common milkweed new, tender leaves are preferred monarch oviposition sites and larval food. In the North East one can have such leaves in July, August, and early September during the main oviposition period in three ways. First, one can grow seedlings. Second, one can cut large shoots to about half their height in June and July before or after they bloom. Third, one can cut large shoots to the ground in June and July. Cut plants often produce new shoots from their rhizomes. It is advisable to let some large, mature shoots remain in summer and fall because large monarch larvae, milkweed tiger moth larvae, and other native species feed on mature leaves. Milkweed bugs commonly feed on follicles. Monarch larvae can consume small seedlings to the ground. To save seedlings, one can transfer larvae from seedlings to larger shoots.

Deforestation due to human settlement may have expanded the range and density of common milkweed. This plant can become invasive; it is naturalized in several areas outside of its native range. However, recently in the United States, milkweed populations have diminished dramatically due to factors such as development and the use of herbicides, which has played a significant part in the monarch butterfly's dramatic population decline. Common Milkweed grows up to six feet tall . It has large broad leaves that are usually four to ten inches long. Common milkweed flowers are pinkish purple clusters that often droop.

Plant common milkweed in a sunny location with good drainage and moist soil. In a few years after planting common milkweed it will start to spread by rhizomes. Simply remove any shoots that are in the wrong place in the garden, leaving at least a few in the garden. This species moves around in its habitat by cloning and sprouting from seeds. Female monarchs frequently lay their eggs on small, tender shoots, and larvae favor such shoots as food. It is valuable to leave at least a few mature shoots in one's garden until early autumn because shoot leaves produce food used by rhizomes which produce shoots in the next year. The nonnative oleander aphid can become abundant on milkweed shoots and stunt them. One can control this aphid by spraying soapy water on aphid groups, then immediately rinsing the groups with plain water. It might take more than one application to the same shoot on different days to control the aphids. The soapy water also kills aphid predators and parasites. However, the aphid outbreaks can be so large, that they can markedly harm milkweeds before their natural enemies control them. To make the soapy water, use 1 teaspoon of a dish detergent, used for hand-washing dishes, per quart of water. Common milkweed seeds require a period of cold treatment before they germinate. Monarch Watch provides much information on rearing monarchs and their host plants.