Any of several closely related species of the genus Lobelia, perennial plants of the lobelia family, native to North and Central America. All bear spikes of scarlet, lipped flowers on leafy stems up to 5 ft (1.5 m) tall. L. cardinalis and L. splendens, considered to be one species by some authorities, are taller than L. fulgens, the Central American parent species of the garden cardinal flower. The blue cardinal (L. siphilitica) is smaller than the others and has blue or whitish flowers.
Learn more about cardinal flower with a free trial on Britannica.com.
Most of these plant species are found either partially or fully submersed in their natural habitat. Although there are a handful of obligate aquatic plants that must be grown in water (Cabomba sp., for example), most grow and thrive fully emersed if the soil is kept moist.
As a very important note, the taxonomy of most plant genera is not final. Scientific names and classifications have changed often in the past years, creating confusion for most aquarists. Most of the old names are still in use today on some web sites.
Common aquarium plant species: