Seeds from this tender perennial Asclepias Curassavica Silky Gold. Grown as annuals in the north. Plants grow 28 inches tall and have flat umbels golden flowers with gold centers, flowers the first year. Plants are loved by butterflies. This is a subtropical plant hardy in zones 9 to 11 is loved by butterflies and those that love cut flowers. 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.