A patch of Lobelia cardinalis growing in a sunny bog.
Cardinal flower, Lobelia cardinalis (pronounced low-BEE-lee-ah kar-dih-NAL-iss), is a perfect choice for damp-to-wet soil, in full or partial sun. Spikes of bright red, tubular flowers burst into bloom in late summer and fall, delighting both the gardener and hummingbirds. Flower spikes open first at the bottom and work their way to the top over several weeks.
With fertile soil and plentiful water, plants may reach as much as four feet tall. Pinch out the growing tips early in the year to make plants shorter and bushier. These natives are perennial in zones 3 to 9, and appreciate a light winter mulch. They tend to be short-lived, lasting two or three years in the Mary Snoddy garden. I have had limited success in attempting to start them from seed. My preferred method is to plant a few purchased plants and allow them to self-sow, which they do freely. I placed three plants at the edge of our pond, did not prune or deadhead, and in a couple of years they had spread around the sunny perimeter to form an impressive display. They can also be propagated by stem cuttings or root cuttings, or by separating and replanting any “pups” that may form at the plants’ base. If you want yours to self-seed, allow the plants to scatter their seeds before removing spent bloom stalks.
There are two theories on how the Cardinal flower got its common name. One is that the plant was named for the scarlet feathers of the Cardinal bird. The other is that the flower color is the same red as robes worn by Cardinals in the Catholic Church. One cultivar, ‘Queen Victoria,’ has bronze foliage that provides an unusual contrast to the clear red blooms. I understand that cultivars with white or rose-pink flowers exist, but I have not found them in local nurseries.
Plants are moderately resistant to damage by deer. The one thing they will not tolerate is dry soil. This makes them ideal candidates for pond-side or bog plantings. Plants are toxic to humans and pets.
Blue Lobelia (Lobelia siphilitica) is similar in appearance and culture, but instead has beautiful blue blooms. Blue Cardinal flower, or Great Blue Lobelia, is damaged by deer more often than its red cousin.
These Cardinal flowers are self-sown from three mother plants sited next to the Mary Snoddy pond.