Tolumnia is a genus of twenty-seven species that spent much of the twentieth century folded into the larger genus Oncidium, identified by the equitant arrangement of their fan-like leaves, each sheathing the next in the manner of iris foliage. In the wild, these miniatures cling to exposed twigs and small branches in dry tropical habitats, experiencing rapid cycles of wetting and drying. Replicating that rhythm is the central challenge of cultivation: the roots need frequent watering, but the growing medium must dry out quickly between sessions. A small bark mount or a tight terracotta pot promotes the necessary airflow.

The flowers are the payoff for this exacting regimen. Sprays of elaborately marked blooms in yellow, orange, red, or white emerge from the leaf axils, each one dominated by a large, semicircular lip that functions like the skirt of a dress, with the column positioned above it like a bodice. Bright light from a south-facing window, warm temperatures, and half-strength liquid fertilizer during active growth keep the plants producing new fans of leaves and, in season, new flower spikes. Watch for mealybugs, scale, and thrips, which find these plants as appealing as any other tropical houseplant.