Ask Mr. Smarty Plants

If you planted the milkweed to attract butterflies, examine it closely for some very small but very colorful caterpillars. We will use Asclepias tuberosa (Butterflyweed) as an example. It is a larval host for Monarch and Queen butterflies, which means the leaves are there to be eaten by the larvae of those butterflies. The flowers attract butterflies and hummingbirds, but they don't eat leaves. We found this paragraph on our webpage on this plant that we think is illuminating:

"Inevitably butterfly weed will get aphids; you can leave them for ladybugs to eat or spray the insects and foliage with soapy water. Aphids can also be removed by blasting the plant with a high pressure stream of water."

Because we know you are hoping to attract the Monarch, please use no poisons on it. See this article from the University of California Integrated Pest Management on Aphids to help you identify the problem and deal with it. Look on the underside of the leaves, and you will probably see both the tiny aphids, tinier eggs and the honeydew they exude, which is farmed by ants, who may also be present. Remember - NO POISONS! - butterflies die from those, too. If you have found any caterpillars, better just leave the plant alone, the water stream could wash the larvae away, too.