Commonly called cardinal flower, perennial lobelia is a easy to grow North American native plant, especially if you have a wet, swampy location for it. The plant has attractive, dark-green to reddish bronze leaves and showy, 3-5′ spikes of brilliant red or blue flowers that bloom from late summer to early fall. Perennial lobelias are useful for difficult wet locations in full sun or partial shade. They make a wonderful choice for landscaping around ponds and streams — anywhere the soil is consistently moist. In fact, lobelia even loves downright wet conditions, making it a top choice for bog gardens. The perennial type of lobelia plants (not to be confused with the low-growing, often blue annual types) are magnets for birds, hummingbirds, and butterflies, so they’re great for wildlife gardens. The foliage is a handsome rich green to sometimes dark reddish purple. The plant produces striking spikes of flowers in all shades of red, pink, blue, and white.
Plant perennial lobelia in a sunny or partially sunny spot with rich, moist soil. In nature, you’ll find these plants in swampy situations so try to match their needs by providing plenty of moisture. In average soil, lobelia can be a little short lived, surviving a couple of years before fading out. In locations with more consistent moisture, it tends to last longer. Lobelia needs humus-rich soil. Mulch with a biodegradable material, such as wood bark or chopped leaves, to add humus to the soil. Add extra interest in your garden by scoping out varieties that have rich bronze or purple foliage throughout the growing season.
Lobelia grows 18 to 24 inches tall and wide, and is relatively deer resistant. It is hardy from zones 3-9. It works well in containers and makes good cut flowers. They are easily propagated to build up impressive colonies by dividing the clumps in early spring, as the new growth is awakening, either using a knife or a pair of digging forks. Perennial lobelias enjoy the same moist soil conditions as primroses, so these – especially the red or pinkish colored varieties – make happy companion plants.