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Scientific Name: Delphinium robustum Rydberg
Vernacular Name: Robust larkspur
R-E-D Code: 1-1-2
Description: Perennial herb 1-2 m tall; stems glabrous or puberulent, sometimes reddish at the base; leaves all on stem and withered from the basal 1/5 of the stem at the time of anthesis, petioles 7-13 cm long, blades 10-20 cm long and 7-12 cm wide, palmately divided into 5 main lobes, each lobe further dissected into additional lobes or teeth that are rounded at the apex or acute with a blunt tooth (mucro); inflorescence of racemes that are paniculately branched at the base in larger specimens, 40- to 100-flowered, branches and pedicels with short hairs; sepals ovate-acute, bluish purple or pale lavender, rarely pink, sparsely pubescent, lateral sepals forward pointing, 9-14 mm long, the upper sepal extended basally into a spur 9-13 mm long; petal blades hairy, cleft, 5-7 mm long. Flowers July to September.
Similar Species: Delphinium sapellonis is morphologically very similar, but has yellowish or brownish-purple flowers that are usually glandular and more densely pubescent. Delphinium ramosum is typically a shorter plant with pubescent lower stems and unbranched racemes. Delphinium barbeyi has longer, yellowish hairs on the pedicels, and dark blue flowers with acuminate lower sepals.
Distribution: New Mexico, Colfax, Rio Arriba, Sandoval and Taos counties, Jemez, San Pedro, San Antonio, and Sangre de Cristo mountains; adjacent south-central Colorado.
Habitat: Canyon bottoms and aspen groves in lower and upper montane coniferous forest; 2,200-3,400 m (7,200-11,200 ft).
Remarks: This tall larkspur is an enigma. Warnock (1997) places it in several northern New Mexico mountain ranges. Yet only two counties (Colfax and Taos) are represented by specimens at the University of New Mexico Herbarium. Most tall species of Delphinium in New Mexico are taxonomically ambiguous and need additional study. This larkspur may not be readily distinguishable from Delphinium ramosum in Colorado (Bill Jennings, personal communication).
Conservation Considerations: Appears to be sporadically distributed and population sizes have never been assessed. Its response to forest fire and grazing have not been studied. Some species of Delphinium are poisonous to cattle, so the genus as a whole is sometimes targeted for poisonous weed control.
Important Literature (*Illustration):
*Ewan, J. 1945. A synopsis of the North American species of Delphinium. University of Colorado Studies, Series D 2(2):55-244.
*Warnock, M.J. 1997. Delphinium, pp. 196-240 In: Flora of North America Editorial Committee (eds.). Flora of North America, Magnoliophyta: Magnoliidae and Hamamelidae, Vol. 3. Oxford University Press, New York, New York.
*Beatty, B.L., W.F. Jennings and R.C. Rawlinson. 2004. Delphinium robustum Rydb. (Wahatoya Creek larkspur): A technical conservation assessment. [Online]. USDA Forest Service, Rocky Mountain Region. Available: http://www.fs.fed.us/r2/projects/scp/assessments/delphiniumrobustum.pdf [accessed September 2011].
Information Compiled By:
Robert Sivinski, 1999; last updated 2011