Iris in many classes can show a beautiful purple staining at the base of their foliage. In cool sunny Spring climates this may extend far up the leaves and sometimes the entire plant may be purple. Many have admired tis trait and tried to enhance it with breeding but result still seem somewhat limited. Certainly a purple foliaged plant would make a great novelty iris.
Most groups show this trait in some members. In the beardless irises this seems to be a possible indicator to separate Iris virginica from its hybrid with Iris versicolor known as Iris Xrobusta. In cool climate countries such as Germany Iris robusta plants may be wholly purple in spring.
A totally purple bearded iris has yet to be recorded but the blue anthocyanin sugars have been known to color stalks and/or spathes in some plants.
The American Dykes Medal 1940 winner Wabash' can be distinguished from the similar 'Bright Hour' because 'Wabash' has purple based foliage.
The Spring 1992 issue of ROOTS has an article and list of purple based foliage irises through 1939 introductions. You can find this article "I.D. Groundwork" by Phil Edinger online at: http://www.worldiris.com/public_html/Frame_pages/Purple.html Note that the previous link no longer works; however you can see it via the Wayback Machine at: http://web.archive.org/web/20140826201903/http://www.worldiris.com/public_html/Frame_pages/Purple.html (which is the most recent snapshot, earlier ones are also available). It also is now available on the HIPS website at: http://www.historiciris.org/articles/id-groundwork-pbf.html as reference material for a new effort to collect purple based foliage information for identification of irises. More information and how to participate at: http://www.historiciris.org/hips-pbf-study/.
We are attempting to develop a list below of Irises with this trait. Please add any that have been missed by commenting in the comment box.