Shasta iris –Iris tenuissima
Range: Northern California foothills around upper end of the Great Central Valley, southern Klamath and Cascade Ranges. From 300 to 6,000 feet elevation.
Original material: Pit River Ferry (today submerged under the eastern arm of Lake Shasta), Shasta County, California, 1912. Named by William Rickatson Dykes for his specimens’ markedly slender flower parts (tenuissima = very tenuous).
Key identifying features:
- Long floral tube; 1½ to 3 inches, tightly enclosed by spathes.
- Floral tube’s upper portion dilated, like the end of an upturned bottle.
- Long, narrow style crests, usually turned back inward.
- Petals and sepals slender and easily broken, their edges often wavy or ruffled.
- Flowers appear rather flat; petals and sepals spread outward.
- Stigma triangular, nearly tongue-shaped.
Flower color: White, cream, pale yellow to golden yellow (the latter perhaps through contact withIris hartwegii), often with darker reddish-brown, lavender or yellow veins; flower tube yellow-green.
Habitat: Shaded, duff-covered forest floor or small sunny openings in oak/pine woodlands.
Name: Comments: The Shasta Iris seems to replaceIris macrosiphon around the northern end of California’s Great Central Valley. Flowers with long style crests and slender, easily broken parts with wavy edges help identifyIris tenuissima, though some flowers have exceedingly narrow parts and others less so.
One name sometimes used for this species – “long-tube iris” – might be more confusing than helpful. Four other Pacifica iris have floral, or perianth tubes as long or longer than those ofIris tenuissima.
Genetic studies confirm thatIris tenuissima andIris chrysophyllaare very close relatives. Their actual relationship and relative distribution in northern California cry out for further study. For years, enthusiasts have used a functional, but less than satisfying device – which we follow here – to separate those growing north of the Siskiyou mountains in Oregon (asI. chrysophylla); from those found south of the Siskiyous in California (asI. tenuissima).
Other features looked at include the floral tube (the diameter abruptly enlarged through most of the upper portion intenuissima, uniform diameter throughout inchrysophylla), the stigma (sometimes finely toothed intenuissima, entire inchrysophylla), and the flower stem (generally longer than 4 inches intenuissima, often shorter than 4 inchrysophylla).
Iris tenuissima purdyiformis: an unusual population
Here is a clear example of how carelessly used labels can cause others serious confusion, unless we keep in mind the difference between a variety and a subspecies. “Variety” is an informal term (like “strain” or “form”), used to recognize that plants are seldom exactly identical. Even within a species, they can come in a wide range of size, form and color. Horticulturalists often seek out particular varieties they especially like to propagate.
Robert Foster noticed that three of his Shasta iris specimens had bract-like leaves wrapping their their stem, something more often seen inIris purdyi, orIris bracteata. So he called the variety “purdyi-like” (purdyi + formis). Unfortunately, in giving them a name he used the Latinized three-part format which is preferably reserved for use when formally describing a subspecies.
Biologists have a strict understanding of the word “subspecies”. Within the entire range of a species, sometimes there are certain local populations that–because of their own slightly different history–have an unusual appearance or genetic makeup compared to the others.
Once those plants, and the ways they differ from all the other populations, are well enough understood, a researcher might designate them as a sub-species, and assign them a three-word Latinized name. The first is the name of the genus, the second of the species, and the third word is that population’s own, unique label.But note –When the third and second names are the same, it simply refers back to the original species – it shouldnot be misinterpreted as implying that all the remaining populations make up a unique separate sub-species.
Dr. Lee Lenz found that the Shasta iris growing along the Feather River canyon near Tobin on highway 70 had bract-like leaves enclosing most of the stem. He eventually designated those populations as representing a unique subspecies, and assigned them their formal nameIris tenuissima purdyiformis.
Occasional specimens labeled “I. tenuissima purdyifomis”from other regions are deposited in several museums. We need to keep in mind that Lenz’s use of the wordpurdyiformis is not a descriptive term used to label any specimen of Shasta iris with bract-like leaves along its stem. It’s a unique name – a name he applied only to plants of a specific population living a little ways east of Paradise in the northern Sierra Nevadas.