Castilleja, commonly known as paintbrush, Indian paintbrush, or prairie-fire, is a genus of about 200 species of annual and perennial mostly herbaceous plants native to the west of the Americas from Alaska south to the Andes, northern Asia, and one species as far west as the Kola Peninsula in northwestern Russia. These plants are classified in the broomrape family Orobanchaceae (following major rearrangements of the order Lamiales starting around 2001; sources which do not follow these reclassifications may place them in the Scrophulariaceae). They are hemiparasitic on the roots of grasses and forbs. The generic name honors Spanish botanist Domingo Castillejo.[2]
The species in Castilleja are quite varied in form and lifecycle. The genus includes many species that are completely herbaceous, lacking woody material in their above-ground parts. Though it also includes some slightly woody subshrubs and even a few woody shrubs.[6] They may grow as annual plants, but most of the species are perennial.[7] Their roots are equally diverse in structure ranging from taprootstofibrous root systems. Some species also have modified underground stems called rhizomes to spread short distances.[6]
Stem lengths range from a minute 1 centimeter to as much as 2 meters.[6] In almost all species the leaves are attached to the stems and alternating. The inflorescences are always at the ends of the stems, which may or may not branch.[7] The inflorescence usually have bracts that are brightly colored for the whole length or towards their ends.[6]
Castilleja species are eaten by the larvae of some lepidopteranspecies, including Schinia cupes (which has been recorded on C. exserta) and Schinia pulchripennis (which feeds exclusively on C. exserta), and checkerspot butterflies, such as Euphydryas species.[8][9] Pollinators aid these plants in reproduction, with insects visiting the flowers, as well as hummingbirds for some species.[10]
Castilleja species can play an important role in plant community dynamics and multitrophic interactions. For example, Castilleja hemiparasitic reliance on other plant species may affect competition and dominance among other plant species in its community.[11] Additionally, the foliage of some Castilleja species naturally contains defensive compounds that are sequestered in the tissues of larvaeofspecialist insect species that have developed a tolerance for these compounds and are able to consume the foliage.[8][9] These sequestered compounds then confer chemical protection against predators to larvae.[8][9]
Some species in the Castilleja genus are able to hybridize, especially when ploidy levels match, and hybrids may produce viable seed.[12][13][14] This hybridization potential has been identified as a threat to the genetic integrity of certain endangered Castilleja species.[13]
The author Gregory L. Tilford claims that the flowers of Indian paintbrush are edible. However, these plants have a tendency to absorb and concentrate selenium in their tissues from the soils in which they grow, and can be potentially very toxic if the roots or green parts of the plant are consumed. Highly alkaline soils increase the selenium levels in the plants.[15] In addition Castilleja species will take up alkaloids from other plants when parasitizing them.[16]
^Pennell, Francis Whittier (1951). "Scrophulariaceae". In Abrams, LeRoy; Ferris, Roxana Stinchfield; Vincent, Sylvia; Law, Barbara (eds.). An Illustrated Flora of the Pacific States: Washington, Oregon, and California. Vol. III: Geraniaceae to Scrophulariaceae. Stanford, California: Stanford University Press. pp. 819–820. Retrieved 28 June 2024.
^ abcdeEgger, J. Mark; Zika, Peter F.; Wilson, Barbara L.; Brainerd, Richard E.; Otting, Nick (5 February 2024). "Castilleja - FNA". Flora of North America. Retrieved 7 July 2024.
