Aquilegia, commonly known as columbines, is a genus of perennial flowering plants in subfamily Thalictroideae of the family Ranunculaceae (buttercups). The genus includes between 70 and 400 taxa (described species and subspecies) with natural ranges across the Northern Hemisphere. Natural and introduced populations of Aquilegia exist on all continents but Antarctica. Known for their high physical variability and ease of hybridization, columbines are popular garden plants and have created many cultivated varieties.
Aquilegia plants typically possess stiff stems and leaves that divide into multiple leaflets. Columbines often have colorful flowers with five sepals and five petals. The petals generally feature nectar spurs which differ in length between species. In North America, morphological variations in spurs evolved to suit different pollinators. Some species and varieties of columbines are naturally spurless. In cultivation, varieties bearing significantly altered physical traits such as double flowering are prevalent.
Columbines were associated with fertility goddesses in ancient Greek and ancient Roman religion, and connected to Christian religious concepts. Archeological evidence suggests Aquilegia plants were in cultivation by the 3rd century AD in Roman Britain, and they remain popular in gardens worldwide. Despite often being toxic, columbines have been in use by humans as herbal remedies, perfume, and food. Asian traditional medicine practitioners, Indigenous North Americans, and Medieval Europeans have considered portions of the plants to have medicinal uses. Selective breeding and hybridization of columbines has occurred for centuries, with genetic exchanges between Old and New World species creating further diversity.
Etymology The 1st-century AD Greek writer Dioscorides referred to columbine plants as Isopyrum, a name that is now applied to another genus, Isopyrum. In the 12th century, the abbess and polymath Hildegard of Bingen referred to the plants as agleya from which the genus's name in German, Akelei, derives. The first use of aquilegia with regard to columbines was in the 13th century by Albertus Magnus. In the 16th and 17th centuries, the names Colombina, Aquilina, and Aquileia came into use. With the Swedish biologist Carl Linnaeus's 1753 Species Plantarum, the formal name for the genus became Aquilegia, though limited use of Aquilina persisted in scientific usage until at least 1901.
Several scientific and common names for the genus Aquilegia derive from its appearance. The genus name Aquilegia may come from the Latin word for "eagle", aquila, in reference to the petals' resemblance to eagle talons. Another possible etymology for Aquilegia is a derivation from the Latin ("to collect water"), aquilegium (a container of water), or ("dowser" or "water-finder") in reference to the profusion of nectar in the spurs. The most common English-language name, columbine, is founded in the dove-like appearance of the sepals and derived from the Italian colombino and French colombin, which were in turn derived from columba, Latin for dove.
There are a number of other common names for Aquilegia across different languages. In English, these include granny's bonnet for various species, but particularly Aquilegia vulgaris. An older common name for columbines is lion's herb, from the folk belief that lions fed on it for courage. In French, the word ancolie is the common name for Aquilegia, while individual members of the genus have been called gants-de-Notre-Dame ("Our Lady's glove"). In Italian, amor-nascoto ("love-born") has been used.
Description
Aquilegia is a genus of herbaceous, perennial flowering plants in the family Ranunculaceae (buttercups). The genus is highly variable in appearance. Though they are perennials, certain species are short-lived, with some exhibiting lifespans more similar to biennials and others only flourishing for three to six years. Following a dormant period in the winter, columbines will grow foliage and have a brief flowering period. Some columbines bloom the first year after sowing, others will first bloom in their second year. Later, seed heads will emerge and split, sowing new seed. The foliage lives through the summer before wilting and dying going into the fall.
Aquilegia plants grow from slim, woody rootstocks that comprise the perennial portion of the plants. One or more annual aerial stems rise from the rootstocks each growing season, ultimately drying out following fruiting. Leaves can grow in both basal (from where the plant meets the soil) and cauline (from an aerial stem) arrangements. Leaves emanating from closer to the plant's core are generally borne on flexible petioles, while leaves further from the core generally lack petioles. The compound leaves of Aquilegia are generally ternate, biternate, or triternate. Ternate leaves each divide into three leaflets, biternate leaves divide into three components that each in turn bear three leaflets for a total of nine leaflets, and triternate leaves divide into three components three times for a total of 27 leaflets.
The flowering stems emerge from rosettes during the spring and summer. Each inflorescence appears at the terminus of an aerial stem and can reach long. Depending on the species, an inflorescence will feature one to ten of either cymes (flower clusters) or solitary flowers. Flower morphology varies across the genus, but all columbine flowers emerge from buds that are initially nodding (facing downward). Flowers can be monochromatic or display multiple colors. The typical flower color for columbines is blue in shades ranging into purple and nearly black shades. Blue flowering is especially the norm in European columbines, where only A. aurea possesses yellow flowers. In North America, yellow and red flowers are typical, with blue and blue-purple flowers almost exclusive to high-altitude species.
The perianth (non-reproductive portion) on an Aquilegia flower generally comprises five sepals that look like petals and five true petals. Each petal typically comprises two portions: a blade, which is broad and projects towards the front of the flower, and a nectar spur, which is a nectar-bearing structure which projects backward. The hollow spurs attract pollinators and give columbine flowers a distinctive appearance. Some species possess spurs with hooked, horn-like appearances, while other species can have spurs that are either straight or coiled. Some columbines, such as A. ecalcarata, are naturally spurless. Individuals and populations can also be found with recessive spurlessness within typically spurred species.
Aquilegia are bisexual (featuring both male and female organs) and capable of self-pollination, through either or both autogamy (does not require assistance from pollinators) and geitonogamy (requires pollinators). Autogamy has been observed as the primary fertilization mechanism in A. paui. A. formosa and A. eximia may exhibit adichogamy, where male and female organs do not operate simultaneously to prevent self-fertilization. Fertilization via cross-pollination also occurs in Aquilegia, with pollinators carrying pollen from one flower to the stigma of another.
The reproductive portions of a columbine flower comprise the stamen (male) and gynoecium (female). The stamens, which bear the anthers from which pollen emerges, form a whorl of five around the gynoecium. The total number of stamens varies between species. Aquilegia is the only Ranunculaceae genus where each species has its stamens in a whorled arrangement and has syncarpy (fused carpels) in its gynoecium, with this consistency resulting from the presence of nectar spurs. Generally, there are scale-shaped staminodes between the stamen and female pistil structures. Aquilegia are protandrous, meaning that a flower's anthers release its pollen prior to the flower's stigmas being receptive to pollen. The flowers undergo three stages of anthesis: a premale stage, where the flower perianth is open but the anthers are not dehiscenced (split to expose pollen); the male stage with the perianth present and the anthers dehiscenced, and a postmale stage where the anthers have withered but the perianth remains.
Aquilegia fruit comprises follicles. These follicles have a split on one side and terminate with a curling tip known as a beak. Columbine seeds are generally obovoid with black, smooth exteriors. Columbine seeds are in a dormant state at the point of sowing. Aquilegia seeds remain viable longer than many Ranunculaceae, though germination is faster in newer seeds; in cold storage, A. formosa seeds have remained viable for at least three years. Seed germination is primarily dependent on temperature, with seeds typically requiring a multi-month period of summer temperatures followed by a multi-week to multi-month exposure to winter temperatures (vernalization) prior to germinating once temperatures warm with the arrival of spring. This prevents seedlings from emerging until there are survivable environmental conditions.
The chromosome number for columbines is 2n=14 (seven pairs of chromosomes). Individual plants have been recorded with other anomalous chromosome numbers. It is possible that B chromosomes impact the phenotype and the fertility of the individual plants that possess them.
Phytochemistry
Among Aquilegia that have cyanophores (cells that produce a blue color) like A. vulgaris, the cyanogenic glycosides compounds dhurrin and triglochinin have been observed. Cyanogenic glycosides generally taste bitter and can be toxic to animals and humans. Ingestion of of fresh A. vulgaris leaves by a human was observed to cause convulsions, respiratory distress, and heart failure. A child who consumed 12 A. vulgaris flowers experienced weakness of the limbs, cyanosis, drowsiness, and miosis; all symptoms abated after three hours. Mature seeds and roots contain toxins that, if consumed, are perilous to human heart health.
The presence of the antibacterial flavonoid compound isocytisoside has been observed in A. vulgaris. Polyphenols, primarily flavonoids, are the main component of hydroethanolic extract (produced with a solvent made from a mixture of water and ethanol) from A. oxysepala. These compounds function as antioxidants. A study of A. oxysepala extract found it has a good scavenging effect (a capacity to remove or inactivate undesired substances) on DPPH, superoxide anion, and hydroxyl radicals, but a poor scavenging capacity towards hydrogen peroxide. For all these, ascorbic acid has a superior scavenging effect to the extract.
In flowering plants, the presence of phenylpropanoids can serve as protection from ultraviolet (UV) light and as a signaling mechanism towards pollinators. A study that examined A. formosa flowers determined that the petals and sepals had uniform levels of UV-resistant phenylpropanoids.
Ecology
Despite the plants' toxicity and in the absence of incentives for human consumption, some animals consume the fruit and leaves of columbines. Consumption by mammals is not considered a component of the Aquilegia reproductive cycle but has been observed. In the case of the endangered A. paui, one study cited a personal observation that 30% of all fruit was lost to goat predation.
In the Northeastern United States and Eastern Canada, A. canadensis serves as the host plant for the butterfly Erynnis lucilius (columbine duskywing). In two periods, the first from April to June and the second from July to September, the butterflies lay their eggs on the underside of the columbine leaves. The latterly laid brood overwinters as caterpillars in the plant litter around the columbine. In the Western United States, Bombus occidentalis (western bumblebee) has been observed nectar robbing from A. coerulea by opening or using holes cut in the spurs.