Rocky Mountain Sweetpea - Lathyrus leucanthus
Railroad Canyon, Black Range, New Mexico
May 13, 2014
Whether the Rocky Mountain Sweetpea, Lathyrus leucanthus, is a full species or not is a matter of dispute. Some authorities consider it a variety of Lathyrus lanszwertii. The authorities who wrote "Intermountain Flora" consider the taxonomy of this and other pea species in the region to be problematic, saying that "a settled taxonomy for the complex series of small-flowered mountain [Peas]... will remain unattainable unless differential characters more reliable than those presently known can be found.... The flowers and pods of [these peas are] essentially identical... [but] pubescence..., number and [shape] of leaflets, development of tendrils, and size and color of petals are subject to much variation…."
The BONAP map to the right is for Lathyrus lanswertii. BONAP does not recognize L. leucanthus. On the map, light green indicates that the species is native to and common within the county indicated.
Per Axel Rydberg described the species in 1901 from a specimen he collected in Ojo, Colorado the year before. The species has no scientific synonym but does go by the alternate English Common Name of Nevada Pea.
J. M. Bigelow collected the specimen below while serving on “Lieut. A. W. Whipple’s Exploration for a Railway Route, from the Mississippi River to the Pacific Ocean, near the 35th parallel of Latitude, in 1853-4.” He identified the species as Lathyrus nevadeusis. So goes the life of a specimen sheet, lots of change and annotations over time.
