– Seeds from this Apollo Yellow butterfly plant Asclepias curassavica. This plant has pure golden blossoms and is hardy in zones 8-11 and will bring more butterflies than you can imagine. An added bonus is that this plant is deer proof if that is a problem in your gardens. These perennials grow 4 to 5 feet tall in full sun and sandy soil is best for them. Quite a drought tolerant plant I don’t think that I have ever had to water them. We recommend that tropical milkweed, which can be generally called Asclepias curassavica, should be cut back in the winter and fall months in the southern U.S. and California.