Cardinal flower (Lobelia cardinalis) has brilliant fiery red flowers on dense spikes grow up to 4 feet tall to make this one of the showiest wildflowers. The tubular cardinal red flowers last 4 to 6 weeks and are a favorite with hummingbirds, swallowtail butterflies and sulphur butterflies. Lobelia cardinalis is best planted in rich moist soil in full sun to light shade in a formal perennial bed, moist meadow, water garden, or as a container plant for a patio. The basal rosettes need sunlight in the winter so fallen tree leaves should be removed.