By Susan Harkins

Roger Tory Peterson described this midsummer bloomer as America’s favorite flower, and with good reason. Its blooms are an intense scarlet, which makes it attractive to both us and hummingbirds. You’ll hear Kentucky gardeners refer to Lobelia cardinalis as cardinal flower and red lobelia. Supposedly the name comes from the vestments worn by Roman Catholic cardinals; still others say it’s named for our state bird, the cardinal. The color is spectacular, regardless, as the blooms reflect one of the deepest, truest reds to be found in nature.

With all this natural beauty comes an unfortunate reality: They can be difficult to grow in our own gardens. L. cardinalis isn’t as forgiving as other natives that seem to thrive on our neglect. Providing what it needs is the key to success. But first, let’s take a short botany lesson.

Botany and wildlife

Not only are the red flowers attractive to hummingbirds, but the bloom’s shape plays a part in its success. Each bloom is a long tube, and at the bottom is a few drops of nectar. This shape is perfectly suited to the hummingbird’s long beak and tongue. When a hummingbird visits, it touches its head to the pistil and stamen, (reproductive organs), which stretch beyond the tube’s outer edges.

Culture and propagation

I’m combining these two topics because this is where L. cardinalis is a bit unforgiving. You can plant dozens and they might be gorgeous that first summer, but they might not return the next year—they might never return. Some gardeners love them so much that they treat them as an annual, replanting every year. This species needs good sunlight, but more importantly, moist soil, if you want them to return every year.

Lobelias aren’t true perennials; after setting seed, the stem and root system dies. New plants grow from the plant’s axil (the angle between the upper surface of a leaf and the stem it’s attached to). Although they grow quickly, they remain close to the ground and are obscured by the foliage above. Instead of seeds lying dormant in the soil all winter, you have evergreen seedlings that need tender loving care that first winter.

Keeping the new growth free of debris is vital, otherwise, the small rosettes don’t get the sunlight they require. Unfortunately, many of us add mulch in the fall and winter and unknowingly cover the new rosettes and they starve. Don’t add new mulch to L. cardinalis at this time of year. Instead, look for the new rosettes and remove mulch and debris that cover them. You don’t have to remove mulch from around them, just make sure the new leaves can get sunlight.

Debris is only the first hurdle to jump when trying to cultivate this native in your own gardens. This species self-sows only in moist soil. In Kentucky, that can spell a bit of trouble for gardeners because about the time this flower goes to seed, our climate often dries up. Keep the area moist if you want your flowers to reseed.

Never let them dry out for long. They are one of the few natives that will require additional water during hot spells and droughts. In nature, they grow along streams and ponds, and in swamps and wetlands. They prefer lots of sun but will tolerate and even thrive in shade as long as the soil is moist.

Propagation from both seeds and cuttings is easy. Collect seeds after the pods ripen and split, usually three to four weeks after blooming. It’s common for open blooms to persist toward the top of the stalk while pods near the bottom are ready to drop seeds. Take cuttings of two nodes early in the season so they’ll have time to produce a rosette.

Seeds require 60 days of cold moist stratification. Like many species with small seeds, they need light to germinate, so sow right on top of loose dirt. The seeds are tiny so it’s difficult to control them while sowing. If a new plant tries to bloom its first fall, clip the stalk to encourage more rosette growth.

To increase the chances that your L. cardinalis returns year after year, plant it in good sunlight, keep the area moist, and keep the bed free of debris once you spot new growth. They will thrive in some shade, as long as the soil is moist. It’s not difficult; knowing what to provide is the key. If you’d like a more reliable lobelia, consider Lobelia siphilitica. Its blue blooms are a true blue, the plant adapts well to most gardens, and hummingbirds like it.

Photo credits: Common license via Biodiversity Heritage Library