■ (SPEC) Iris tenuis S. Watson

1882, Botanical author Sereno Watson Iris tenuis

Iris tenuis. (Sereno Watson, 1882, Cascade Mountains, Northwest Oregon); Section Lophiris, Height 12-14" (30-35 cm); Pale lilac flowers, low yellowish undissected ridge; Coll. Iris L. F. Henderson 1881;

See below:

• * References
• * Synonyms
• * Variations
• * Hybrids
• * Distribution and Cultivation

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References:

Sereno Watson, Proceedings of the American Academy 17: 380. 1882; Iris tenuis. Rootstock very slender (a line or two thick): stems 8 to 10 inches high, with 2 or 3 bract-like leaves 2 or 3 inches long, 2-flowered ; the longer leaves of the sterile branches of the rootstock equalling the stems and 4 to 6 lines broad : bracts contiguous, the longer about equalling the slender peduncles (2 to 4 inches long): flowers "white, lightly striped and blotched with pale yellow and purple; perianth-tube 2 or 3 lines long, the segments naked, slightly spreading, oblong-spatulate, the outer 15 lines long, a little exceeding the emarginate inner ones : ovary 3 lines long. — Discovered by L. F. Henderson in 1881 on Eagle Creek, a branch of the Clackamas River, Oregon.
Garden & Forest 1: 6. 7.March 1888
Lenz followed Clarkson in excluding it from Californicae, and most recently, Clarkson (1958) has created a new subsection for this one species, calling it the Oregoneae. As already pointed out, the appearance of I. tenuis clearly shows little affinity to the Californicae species, no more so than to almost any other iris species. Quite possibly it was only classified with these in the first place because of its occurrence with one of them, I. tenax. Its differences are in foliage, which is relatively, broad, and soft-textured, and which is entirely deciduous in early fall; in rootstock, which while a slender rhizome, produces one to several stolons annually, each of which may be several inches to a foot or more in length, allowing the plant to form a matted colony rather than a tight clump; in stem, which is deeply forked, producing two to three blossoms in thin scarious spathes; in flower, a tiny, flat, dainty one, palest mauve to white, with a few purplish-brown lines, and a golden yellow median ridge on the falls, appearing rather like a flower of I. cristata. The capsule differs in texture, size, and shape, and in the manner of dehiscing, and the seeds themselves are much like those of I. cristata and I. lacustris. This combination of characters gives an appearance much like the small Evansias mentioned, but particularly to the Japanese I. gracilipes in its taller, deeper forked stem. Although there is no actual crest as in the Evansias, the median ridge is very distinctly well out onto the fall. Only in the absence of a true crest does it not resemble the Evansia irises. Described originally as occurring only on the Clackamas River, it has more recently been found also on the adjoining Molalla River, to the west. This limited distribution-so far from I. cristata and further yet from I. gracilipes-is as strange as its midway appearance. Nevertheless, it is a charming plant in the woodland garden and is very hardy.
James 1926; Mayfair 1926;
Bulletin A.I.S. 55: 91. February 1935 with illustration
Starker 1939
B. LeRoy Davidson offered the following notes in the Bulletin of the American Iris Society p, 26-27. "Among irises, as perhaps in few other genera of plants, are found a number of clear-cut species which are singular in being themselves quite non-varying and at the same time entirely distinct from all other irises. This can be taken as an indication that speciation in certain directions has long ago reached its limits, just as in other directions, i.e., the Pacific coast irises, it is still going on. Iris tenuis is one of these anomalies".
Lenz in his recent revision of Californicae excludes it saying: "... an interesting little endemic from Clackamas County, Oregon ... usually... placed with the Californicae, although some authors have done so with hesitation.
Dykes says "at once distinguished from all other irises from Western America by its deeply forked stems."
R.C.Foster in his treatment of North American irises says: "This very distinct little endemic species is so unlike other members of the subsection that it is with some hesitation that I leave it in association with them."
Clarkson (1955) in his study of the Oregon species removed it from the Californicae, saying: "...clearly it does not belong in the subsection with the other members of the Californicae'-a conclusion that anyone who has studied the plants carefully could not possibly question. Iris tenuis differs in almost every respect from other members of the group. In addition to its great morphological differences, it also has a very different chromosome number than members of Californicae, I. tenuis having 2n=28 as contrasted with 2n=40 for all known wild forms of the Californicae. No hybrids involving I. tenuis have ever been found in nature although in places it grows in association with I. tenax.
Smith and Clarkson (1956) attempted to cross the two species under controlled conditions, but in all instances the pollinations resulted in failure."

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Chromosome counts

2n=28, Simonet, 1934; 2n=28, Lenz, 1956; 2n=28, Smith & Clark, 1956. ----

Variations

no registered variations; Photos of large colonies show there is quite a bit of variation from whites to purples. ----

Hybrids

There are no reported hybrids, It maybe possible to cross tenuis with species in the series Chinensis-RP ----

Distribution and Cultivation

Distribution: The distribution of the species gives clues as to its cultural requirements, although plants in cultivation can often tolerate a wider range of variables: The species is found in the following region: Bonap's North American Plant Atlas shows the following map reproduced by permission of Kartesz, J.T., The Biota of North America Program (BONAP). 2015. Taxonomic Data Center. (http://www.bonap.net/tdc). Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2015. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)]
Cultivation;

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-- Main.RPries - 2010-02-23