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    Linnaeus named the Lathyrus genus in 1753.  "Lathyrus" is, according to William Weber, Greek for "very passionate" and refers to the ancient belief in the plantís supposed aphrodisiacal powers.  

   Click for a photograph of a field of Lathyrus lanszwertii.

Lathyrus lanszwertii variety leucanthus
Lathyrus lanszwertii variety leucanthus.    Synonym: Lathyrus leucanthus.   (Lanszwert's Sweetpea)
Fabaceae (Pea Family)

Montane, subalpine. Woodlands. Summer.
Horse Creek Trail, June 25, 2004.

From low to high elevations this is an extremely common pea in the Western San Juans (and from Montana south to New Mexico and west to the Cascades and Sierras).  Although flowers are usually white, they often have tinges of pink and rust, especially as they fade.

Precise classification of this and similar peas is quite difficult.  According to Intermountain flora: "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 specific epithet, leucanthus, is derived from Greek: "Leuc", "white" and "anthus", "flower".  Kartesz, Welsh, and the Intermountain Flora accept the specific epithet, "lanszwertii" for this plant.  Louis Lanszwert (1825-1888), was a San Francisco pharmacist. 

Lathyrus lanszwertii variety leucanthus
Lathyrus lanszwertii variety leucanthus.    Synonym: Lathyrus leucanthus.   (Lanszwert's Sweetpea)
Fabaceae (Pea Family)

Montane, subalpine. Woodlands. Summer.
Colorado Trail above Roaring Fork, June 29, 2006.

Patches of plants with three inch long linear leaves occasionally mix in with the far more common inch long elliptical leaves shown above.

Lathyrus lanszwertii variety leucanthus

Lathyrus lanszwertii variety leucanthus

Lathyrus lanszwertii variety leucanthus

Lathyrus lanszwertii variety leucanthus

Lathyrus lanszwertii variety leucanthus.    Synonym: Lathyrus leucanthus.   (Lanszwert's Sweetpea)
Fabaceae (Pea Family)

Montane, subalpine. Woodlands. Summer.
Little Taylor Creek Trail, May 31, 2006 and Lizard Head Trail, June 9, 2006.

Lathyrus lanszwertii variety leucanthus
Lathyrus lanszwertii variety leucanthus.    Synonym: Lathyrus leucanthus.   (Lanszwert's Sweetpea)
Fabaceae (Pea Family)

Montane, subalpine. Woodlands. Summer.
Robertson Pasture Trail, Abajo Mountains, Utah, June 12, 2009.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Lathyrus lanszwertii