|Asclepias speciosa (Photo: Wikipedia Commons)|
There are well over 100 species of milkweed, but only a few are native to the Northwest. Most species are toxic to vertebrate herbivores if ingested due to cardenolide alkaloids contained in the leaves and stems. This toxicity makes the Monarch caterpillar and butterfly unpalatable to potential predators. Asclepias speciosa is said to be the least toxic of the milkweeds. Named by Carl Linnaeus after Asclepius, the Greek god of healing, it’s an unusual plant in a number of ways. Its pollen is grouped into pollen sacs (pollinia), rather than being individual grains as is typical of most plants. “The feet or mouthparts of flower-visiting insects such as bees, wasps and butterflies, slip into one of the five slits in each flower formed by adjacent anthers. The bases of the pollinia then mechanically attach to the insect, pulling a pair of pollen sacs free when the pollinator flies off.” Its sap contains latex and milkweed filaments offer good insulation properties. Milkweed is grown commercially as a hypoallergenic filling for pillows. And Native Americans used it as a source of sweetener due to the high dextrose content of its nectar. [Source: Wikipedia]
If you have a sunny location, milkweed is worth planting for the fragrance and flower form, but it is also worthwhile planting to help save the migrating Monarch butterfly population.
For more information on milkweed and its importance to the survival of Monarch butterflies, check out these sources: Wikipedia, Monarch Joint Venture and Monarch Watch. For information on butterfly gardening, visit the North American Butterfly Association’s website. Click here for information about Monarch butterflies.