Lippia dulcis. Tender perennial herb used by the Aztecs to treat coughs, colds and other lung ailments. Leaves are 1000 times sweeter than sugar, but contain too much of toxic camphor to be a sugar substitute. White flowers. Good ground cover or in hanging baskets. Grows 6-12" tall, sprawling to 48". Blooms spring through summer. Sun to shade. Plant in moist yet well-drained soil. Annual except in zones 9-11.