The blue lobelia is a flowering plant with intensely blue flowers. One variety of lobelia, L. siphilitica, is called the great blue lobelia. Its blue flowers can persist for a month or more. The lobelia is also called the cardinal flower.
Great blue lobelia grows in soil with adequate moisture and tolerates "wet feet." It needs lots of organic matter and grows to between 2 and 3 feet high with a spread of between 1 and 1 1/2 feet. It thrives in full sun to part shade and needs little care. Flowers arrive from July until September. Lobelia is a perennial and easily self-seeds.