Trimezia is a genus of about 20 species from the warmer parts of Central and South America and the West Indies in the Iridaceae family. Plants are evergreen or seasonal perennials that grow from either an erect rhizome or a corm and have iris-like fans of leaves and short lived flowers not unlike Cypella with three larger outer segments and three small inner ones. Most are yellow, spotted and banded with brown or purple in the center. Most are summer growers with a rest period in winter. Another related genus sometimes included in this genus is Neomarica. Species probably need the protection of a greenhouse in winter and should not be allowed to dry out completely during this time. The two species pictured below are widely cultivated in the tropics and subtropics.
Trimezia martinicensis is a species from the West Indies with yellow to golden flowers that are marked bronze at the base. According to the description from Clive Innes' book plants grow from 20 to 40 cm. Leaves are narrow, flattened, slender, to about 30 cm. The stems are erect, terete, glabrous. Several short-lived flowers are produced in succession. The outer segments are erect or incurved and the inner segments smaller, folded inwards, yellowish or brownish yellow. Most of the plants grown under this name are really Trimezia steyermarkii. This blog has a photo of what seems to be a correctly identified species. The photos we have had on the pbs wiki in the past illustrating this species have now been renamed T. steyermarkii.
Trimezia steyermarkii was identified by Alberto Castillo in the first photo as the plant blooming for Lee Poulsen in September 2003 in a pot without a label. Alberto states it is a well known Caribbean plant widely used in landscaping in the New World tropics and frequently misidentified as Neomarica longifolia or Trimezia martinicensis. Clive Innes' book describes it as having leaves that are ensiform, thin textured with a prominent mid-rib and yellow flowers with purple and brownish-purple bands. Photos 2-4 from Mary Sue Ittner who notes that individual flowers are very short lived (part of a day), but blooming continues over a long period. Photo 2 shows the plant, photo 3 the open flower, and photo 4 the flower from the side. The final photo was taken by Andrew Harvie.