A stunning, upright stalk of brilliant red blooms earns cardinal flower’s distinction as one of North America’s most recognizable and beloved wildflowers. It is renowned as a standout in the garden or in its natural habitat. This native perennial, botanically known as Lobelia cardinalis, was so admired by early explorers of our continent that it made its way to Europe in the 17th century. The genus is named to honor Matthias de l’Obel, a Flemish botanist. The species name (as well as the common name) reflects the bloom’s similarity in color to the scarlet robes of cardinals.
Cardinal flower is an excellent addition to the pollinator garden. The striking red blooms prove irresistible to hummingbirds, which are cardinal flower’s primary pollinator. In a mutually beneficial arrangement, as the hummingbird sips nectar from within the flower’s tubular base, the anthers dangle above the bird’s head, depositing pollen there, which is then transferred to the stigma of the next visited flower, resulting in pollination.
The flowers are also popular with butterflies that have tongues long enough to access the nectar. This includes several species of swallowtails. In my own garden, I find that the yellow sulphur butterflies are especially fond of the blooms.
Cardinal flower is in the bellflower (Campanulaceae) family. However, the flower is not what we think of as a typical bell-shaped form. Instead, the 1- to 2-inch bloom is bilaterally symmetrical with two lips. The upper lip has two lobes, and the wider, spreading lower lip has three. These blooms are densely borne on erect, unbranched spikes that typically reach 2 to 4 feet tall. Along the stem are interspersed leaves with an irregularly toothed edge. Blooming begins in mid to late summer and extends a month or more, with flowers opening sequentially up the spike.
Flowers are followed by round seed capsules that turn from light green to brown as the seeds mature. The seeds are tiny, numerous, and cinnamon-brown in color, and they remain in the capsules until they finally sift out through small holes in the top. After the bloom season is over, a low rosette of leaves that are 2 to 6 inches long remains evergreen throughout winter. It is essential to keep this rosette of leaves clear of fallen leaves or mulch. If the plant gets smothered or is deprived of sunlight, it will not survive.
Cardinal flower’s preferred habitats are open moist to wet areas, such as stream banks, damp meadows, marshes, roadside ditches, and low woodlands. It has an extensive natural range, occurring throughout much of the eastern half of the United States and into Canada.
Cardinal flower can be grown in average garden conditions, but to keep it happiest, take a cue from its natural habitat and provide ample moisture. It will even tolerate occasional standing water, making it useful for areas with drainage problems. It is also suitable for growing along the edges of ornamental ponds or in bog gardens. It adapts well to container cultivation if adequate water is provided. Cardinal flower prefers garden sites with sun to light shade, though it will appreciate protection from the intense afternoon sun.
In the garden, cardinal flower mixes well with other native plants that require similar conditions. These plants include its relative, great blue lobelia (Lobelia siphilitica), Boltonia (Boltonia asteroides), ironweed (Vernonia spp.), scarlet rosemallow (Hibiscus coccineus), swamp sunflower (Helianthus angustifolius), turtlehead (Chelone spp.), and green-head coneflower (Rudbeckia laciniata).
Though considered a perennial, cardinal flower is often short-lived. Fortunately, it readily and naturally reseeds if conditions suit it. If you want to help it along, simply collect the tiny seeds when the seed capsules are brown and dry. Sow the seeds in flats or directly in the garden, and take care not to sow them too densely. The seeds of cardinal flowers must have light to germinate, so they should not be covered with soil. A cardinal flower plant may also naturally produce offshoots from the basal rosette of leaves. These small plants can be separated from the mother plant in fall or spring and transplanted into the garden.
Seeds and plants are usually available at Cherokee County Master Gardener plant sales and from numerous online sources specializing in native plants. So if you don’t have a cardinal flower in your garden yet, take the opportunity to add it. You will appreciate its beauty, as will the hummingbirds.