Aquilegia coerulea, commonly called the Colorado columbine, Rocky Mountain columbine, or blue columbine, is a species of flowering plant in the buttercup family, native to the Rocky Mountains in the western United States. It is a moderate sized wildflower that grows in mountainous areas from the foothills to above timberline. The flowers are mainly pollinated by bumblebees and several species of hawkmoths. The species has been the state flower of Colorado since 1899 and with its large, showy flowers is a frequent garden plant and used in the breeding of columbine hybrids. The botanical name coerulea (or caerulea) means 'sky blue'.
Description Aquilegia coerulea is a herbaceous plant with flowering stems that may be when fully grown. They are perennial plants that typically live for four to six years; regrowing from a simple or branched rootstock that is covered in the bases of old petioles, the stems that support individual leaves. The basal leaves, the ones growing from the base of the plant, are always shorter than the flowering stems, just tall. They are compound leaves that are usually biternate, having nine leaflets in total in groups of three. However, occasionally they may be simply trifoliate, divided into just three leaflets, or tripinnate with each leaf divided to three levels with 21 leaflets in total. Each leaflet is quite thin and has three . On their upper sides they are green and , smooth and hairless. They may either be glabrous or , covered in fine, minute hairs, on the undersides. Leaflets most often range in size from , but occasionally may be as long as .
In the wild, blooming can commence as early as late April and might occur as late as early September, though usually plants are not found in bloom earlier than May. Mature plants grow one to ten flowering stems, though averaging three to four, each with three to four flowers. The flower furthest out on a stem opens first and then each opens in sequence downward. The plant flower buds nod, facing somewhat downward. The flowers are large and showy with a diameter of as much as , but more often about . Flowers tend to be smaller on plants growing at higher elevations. They are so striking that the botanists E. O. Wooton and Paul C. Standley enthusiastically wrote of them in their 1915 Flora of New Mexico, The flowers are atop stems, ones that stand perpendicular to the ground, and have five large, spreading sepals that resemble petals in shades of white to deep-blue or occasionally pink in their wild condition. The sepals range in shape from a flattened circle with somewhat pointed ends with the widest part moved toward the base (-) to like a somewhat egg shaped spear head (-ovate). They range in size from 2.6 to 5.1 cenimeters long and 0.8–2.3 cm.
The five petals have very long tapered spurs, ranging from 2.5 to 7.2 centimeters in length, though usually longer than 3.4 cm. The spurs are almost straight, but curve outwards slightly and end in a small knob at the tip. The blades of the petals are 1.3–2.8 cm long by 0.5–1.4 cm wide. Petals are most often white to cream in color at the front with the spurs having the same range of colors as the sepals. The flowers are scented and produce more volatile molecules during the day than in the evening.
The center of the flower has a projecting cluster of numerous bright orange-yellow stamens, 50–130 total. The flowers are protandrous, developing pollen before the stigma becomes receptive. The stamens range in length from 1.3 to 2.4 cm. They surround three to ten unfused carpels with flowers most frequently having six, but varying even on the same plant. If fertilized each of the carpels may develop into a , a dry pod that splits along one side. Each of the pods is round in cross section and is filled with small, smooth, black seeds. Both the number of pods that develop and the number of seeds in the pods decrease for flowers that bloom later on a plant.
The leaves may be mistaken for that of a meadowrue (Thalictrum), but the flowers are entirely different and the species cannot be confused while flowering. Similar columbines in its range include rock columbine (Aquilegia scopulorum), blue limestone columbine (Aquilegia jonesii), Mancos columbine (Aquilegia micrantha), and dwarf blue columbine (Aquilegia saximontana). Rock columbine has leaves that are covered in natural waxes making them blue-green () rather than green. It is found in Nevada and Utah. Blue limestone columbine has much shorter spurs on its flowers, just 0.8–1.5 cm and grows to the north in Wyoming, Montana, and Alberta. Mancos columbine has , very sticky, leaves. Dwarf blue columbine is only found at very high elevations in rocky areas and has strongly hooked spurs about long as well as being a smaller plant.
Taxonomy
Aquilegia coerulea is classified in genus Aquilegia in the family Ranunculaceae. A 2013 study found that it is most closely related to Aquilegia elegantula, Aquilegia skinneri, and Aquilegia longissima, with all columbine species from the Americas likely splitting from their Eurasian relatives in the Middle Pliocene some 2.3–5.5 million years ago. In Utah the species is documented to hybridize with Aquilegia elegantula, Aquilegia flavescens, and Aquilegia formosa.
The first scientific description of Aquilegia coerulea was by the American scientist Edwin James in 1822. Though Aquilegia coerulea was the original spelling by James, it has often been spelled as Aquilegia caerulea as this is more correct Latin. However, the rules of taxonomic nomenclature generally prefer the original spelling and this is the name adopted by the Board of International Botanic Nomenclature. James found the first specimen he collected in a thicket of scrub oak near what is today Palmer Lake, Colorado, while on the Stephen H. Long Expedition of 1820. After James's description seven species, six subspecies, five varieties, and two botanical forms have been described that are considered to be synonyms of the species or one of its four varieties.
Table of Synonyms Name Year Rank Synonym of: Notes Aquilegia advena 1856 species var. coerulea = het. Aquilegia caerulea 1823 species var. coerulea = het. orth. var. Aquilegia canadensis subsp. coerulea 1893 subspecies Aquilegia coerulea ≡ hom. Aquilegia coerulea subsp. albiflora 1918 subspecies var. ochroleuca ≡ hom. Aquilegia coerulea var. albiflora 1895 variety var. ochroleuca ≡ hom. nom. superfl. Aquilegia coerulea subsp. alpina 1918 subspecies var. alpina ≡ hom. Aquilegia coerulea subsp. daileyae 1918 subspecies var. coerulea = het. Aquilegia coerulea var. daileyae 1897 variety var. coerulea = het. Aquilegia coerulea f. glandulosa 1891 form var. coerulea = het. Aquilegia coerulea var. leptoceras 1909 variety var. ochroleuca ≡ hom. nom. superfl. Aquilegia coerulea var. macrantha 1893 variety var. coerulea = het. Aquilegia coerulea f. pallidiflora 1891 form var. coerulea = het. Aquilegia coerulea subsp. pinetorum 1918 subspecies var. pinetorum ≡ hom. Aquilegia formosa subsp. coerulea 1893 subspecies Aquilegia coerulea ≡ hom. Aquilegia formosa var. macrantha 1893 variety var. coerulea = het. Aquilegia leptoceras 1834 species var. ochroleuca ≡ hom. Aquilegia macrantha 1838 species var. coerulea = het. Aquilegia oreophila 1902 species var. coerulea = het. Aquilegia piersoniana 1934 species var. coerulea = het. Aquilegia pinetorum 1910 species var. pinetorum ≡ hom. Notes: ≡ homotypic synonym; = heterotypic synonym
Varieties There are four widely accepted varieties of Aquilegia coerulea according to Plants of the World Online, World Flora Online, and World Plants. Though World Plants additionally lists Aquilegia coerulea var. daileyae as valid as does the USDA Natural Resources Conservation Service (NRCS) PLANTS database. However, in the Intermountain Flora Volume Two, Part A published in 2012 the authors only recognized two varieties, coerulea and ochroleuca. They wrote of the other varieties, "To us, the sizes of the spurs, stamens, and petals are too variable to sort into meaningful varieties."
Aquilegia coerulea var. alpina This variety was scientifically described by the botanist Aven Nelson in 1896. It is known by the common name of Colorado alpine columbine. Though botanical writers such as Robert Nold doubt the validity of the variety. It differs from the other varieties by having much smaller petal blades, only 1.3–1.7 centimeters instead of 1.9–2.8 centimeters. It grows on open rocky slopes in the state of Wyoming at elevations of . It always has pale blue sepals and flowers from June to August. NatureServe has not evaluated the variety since 2001, but at that time they listed it as vulnerable (T3), but they also list it as possibly extirpated from Wyoming and with an unevaluated status in Utah.
Aquilegia coerulea var. coerulea
Five species were described at various times that are considered heterotypic synonyms of this variety. According to the Flora of North America the autonymic variety of the species only grows in Wyoming, New Mexico, and Colorado at elevations of . However, the NRCS PLANTS database lists it in the states of Idaho, Montana, and South Dakota, without giving any specific information about the locations where it grows.
It is distinguished from the two following varieties by having medium to deep blue sepals where they have white, pale blue, or pink sepals. Its sepals range in length from 2.8 to 5.1 centimeters. The petals have spurs that are 3.4–4.8 cm long while their blades are usually 2.0–2.4 cm, though occasionally as short as 1.7 cm. They grow on rocky slopes, near streams, in open woodlands, and in herb dominated meadows. They flower in the summer starting in mid-June and may flower as late as early September. NatureServe evaluated the variety in 2004 and found it to be apparently secure (T4) globally and in Wyoming. They did not evaluate the rest of its range.
Aquilegia coerulea var. daileyae
This disputed variety was described by the botanist Alice Eastwood in 1897. It is a variation where the petals lack spurs and both the petals and spurs are colored deep blue and commonly called spurless columbine, but is also sometimes called Dailey's columbine or star-flowered columbine. Most species of columbine occasionally produce these 'stellate' forms. The spurless columbine may be found in identical habitats to var. coerulea, but only in the state of Colorado. From the foothills to alpine areas forest openings. Part of the reason for its persistances is a lower level of the flowers being eaten by various herbivores such as deer, caterpillars, and aphids.
Colorado resident Anna Dailey collected specimens of the spurless columbine near Evergreen, Colorado and sent them to Eastwood. A genetic mutation causes the petals to be replaced with a second set of sepals. The population continues to reproduce in and near the Reynolds Park open space in Jefferson County, Colorado. They are also found around Estes Park, Colorado near Rocky Mountain National Park. Though lacking parts to produce nectar the flowers are still pollinated by bumblebees, which collect pollen from the plants. When NatureServe evaluated it in 1991 as a variety they rated it as imperiled (T2).
Aquilegia coerulea var. ochroleuca
William Jackson Hooker described this variety in 1864. It had previously been described as a species by Thomas Nuttall in 1834 with the name Aquilegia leptoceras. This species name was also unnecessarily reclassified as Aquilegia coerulea var. leptoceras by Aven Nelson in 1909. It was inadvertently described by Asa Gray as Aquilegia coerulea var. albiflora in 1895 from which it was reclassified by Edwin Blake Payson as a subspecies in 1918. It was not recognized as a distinct variety of the species in A Utah Flora in 1987 and by Alan T. Whittemore in 1997.