Grown as annuals in the north. Pint plant of Asclepias Curassavica Blood Flower. They blossom in zones 4 to 11 throughout the season and will bring all types of butterflies. These plants are perennials and grow 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 it. 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.