Iochroma is a genus of approximately 34 species of shrubs and small trees in the nightshade family Solanaceae, native to the forests of Mexico and South America, with the greatest diversity concentrated in the Andean regions. The genus was established by George Bentham in 1845 and is placed in the subtribe Iochrominae, alongside the closely related genera Dunalia, Eriolarynx, Saracha, and Vassobia. As of 2023, the formerly separate genus Acnistus is treated as a synonym.
The plants are distinguished by their showy tubular to trumpet-shaped flowers, which come in a wide range of colours including blue, purple, red, yellow, and white. These blooms are adapted for hummingbird pollination, and the plants are popular garden ornamentals for attracting wildlife. The calyx is cupular (cup-shaped) and inflated in some species; leaves are alternate, simple, and entire. Fruits are pulpy berries.
Many Iochroma species are cultivated as ornamental garden shrubs and container plants. In cooler temperate zones (USDA zones 7–9) they are grown as patio or conservatory specimens, while in warmer zones (9–10) they can be planted directly in the landscape. Most species are not frost-hardy and require overwintering under protection. Plants are often trained as standards to manage their size.
Like other members of Solanaceae, Iochroma species contain phytochemicals of pharmaceutical interest, including withanolides and hydroxycinnamic acid amides, though the genus has not been exhaustively studied. Iochroma fuchsioides has a documented ethnobotanical use among the Kamsa people of the Sibundoy valley in the Colombian Andes.
Taxonomy Notes
Iochroma was established by George Bentham in 1845 and belongs to the subtribe Iochrominae within Solanaceae. The genus is currently divided into three sections (Iochroma, Lehmannia, and Spinosa), with several species unclassified to section. As of February 2023, Acnistus is treated as a synonym of Iochroma, and several former species have been moved to Eriolarynx, Trompettia, and Trozelia.
Distribution
Iochroma species are native from Mexico south to Brazil, with the greatest concentration of diversity in the Andean forests of South America, particularly in Colombia and Peru. They grow naturally in montane forest habitats.
Cultivation
Iochroma plants are valued as flowering ornamentals. In temperate zones (USDA zones 7–9) they are best grown as patio shrubs or conservatory plants overwintered under frost-free conditions; in warmer zones (9–10) they can be used as permanent landscape shrubs. Plants are commonly trained as standards to control size and promote a neat form. Their tubular flowers attract hummingbirds and bees. Several wild-collected forms and garden hybrids have been given cultivar names.
Cultural Uses
Iochroma fuchsioides is used by the medicine men of the Kamsa people of the Sibundoy valley in the Colombian Andes as a diagnostic aid, despite its unpleasant side effects. More broadly, the genus contains withanolides and hydroxycinnamic acid amides that have attracted pharmaceutical research interest, though the genus as a whole has not been exhaustively studied.
