On my walk to the local park this morning I saw that a milkweed patch (Asclepias vestita, Woolly Milkweed) had burst into bloom over the weekend.
No butterflies flitted by, but several hummingbirds sat guard over it from nearby oaks. The patch looks very healthy in spite of the drought, and I imagine that this local species is adapted to California’s periodic–sometimes very long periodic–dry years. I plan to go back later and check for butterflies. I’ve seen a few butterflies in my backyard but no monarchs.
Seeing the milkweed this morning reminded me of an article in the March 2015 Natural History magazine. Researcher Dara A. Satterfield from the University of Georgia in Athens found that Monarchs in some areas are overwintering in the United States instead of migrating to Mexico. Rather than traveling south, the butterflies spend the winter feeding and breeding on tropical milkweeds planted in gardens. The tropical milkweed is not native to the United States and doesn’t die back as the native milkweeds do. The researchers found that the non-migrating monarchs have much high levels of a protozoan parasite that results in “deformed wings, shorter lifespans, and decreased breeding” when it infects the monarchs. These infected butterflies could spread the disease to healthy migratory monarchs.
The article says that gardeners need to plant milkweed to help monarchs, but it should be the native kinds that grow naturally in the local area. Unfortunately, you can’t just go down to the local garden shop and pick up milkweed seeds. However, the Xerces Society a non-profit group working for invertebrate conservation has a milkweed seed supply finder that can help you find where to buy milkweed seeds that are native to your area of the USA.