Seeds from Silky Deep Red Asclepias. A tender perennial with bronze tinted foliage. Grown as annuals in the north. Plants grow 28 inches tall and have flat umbels of red flowers with red hoods and gold centers, flowers the first year. Plants are loved by butterflies. Soak seed in warm water for 24 hours sow and lightly cover, germination in 5-20 days. This is a subtropical plant that will flower very well the first year and be loved by Butterflies and those that love cut flowers. Zones 8 – 11. 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.