Asclepia is a carefree, long-lived N. American native that is highly resistant to deer and quite drought tolerant. Dense clusters of blazing yellow blooms are produced from early summer through early fall, with even more encouraged by dead heading.
All of these sterling qualities are nearly beside the point for this special plant. Asclepias is the only plant the monarch butterfly will lay her eggs on - thus is it a crucial ingredient to supporting monarch populations. Plant Asclepias and expect your garden to become very popular with a variety of butterflies and hummingbirds. And when the monarch's eggs hatch, her many caterpillars will feed off this plant, which nourishes them to the point they are ready to enter that magical transition from caterpillar to butterfly.
Please don't spray insecticide on your asclepias, and accept proof of caterpillar sustenance - i.e. "damage" - as a clear sign that you and your garden are playing an essential role in the wonder of the natural world. Expect and celebrate evidence of feeding caterpillars - they are the next generation of monarchs!Enjoy!