Yellow Walking Iris

Trimezia steyermarkii Foster

(With comments on T. martinicensis and "Neomarica longifolia.")

try-MEEZ-ee-ah mar-tin-ah-CEN-sis stie-er-MARK-ee-eye

Iridaceae

Explanation of name:  Julian Steyermark was a prominent botanist known mostly for work on Missouri plants and later in life on Venezuelan plants.

Natural range:

Recognition:  There is widespread confusion among the names Neomarica longifolia and Trimezia martinicencis.  A third name, Trimezia steyermarkii, is relevant to this mix as well.   The commonly cultivated Yellow Walking Iris with yellow flowers, the petals marked with brown, atop a round or only slightly flattened stalk is often erroneously called Neomarica longifolia in horticultural publications.   True Neomaricas have inflorescence stalks as flat as the leaves.  A large number of photographs in books and on web sites are apparently misidentified.   The common species with the round or nearly round inflorescence stalks belongs to Trimezia, with two similar yellow-flowered species being T. martinicensis and T. steyermarkii.  Dr. Peter Goldblatt of the Missouri Botanical Garden graciously helped straighten out the identities of photographs relating to the present discussion.

From Dr. Goldblatt:

Trimezia martinicensis is very different from T. steyermarkii, the latter has larger flowers, pale yellow spotted with brown, the broad leaves are 2-ranked, as they are in T. martinicensis, which I think has suberect inner tepals, and a smaller, but yellow flower. The tepal limbs of both whorls of T. steyermarkii are spreading and somewhat equal.  

This would place most of the commonly cultivated material usually identified in horticulture as Neomarica longifolia or as T. martinicensis as T. steyermarkii. 

Landscape uses:  Spreading flowering perennial for flower gardens, containers