Nematanthus is a genus of flowering plants in the family Gesneriaceae (order Lamiales), comprising around 30 species, all of which are endemic to Brazil. The genus is best known by its common names goldfish plant and guppy plant, which refer to the distinctive pouched orange or red flowers that recall the rounded body of a goldfish.
In their native habitat, Nematanthus species grow primarily as epiphytes on tree bark or in humus-filled rock pockets in humid forest environments. They are perennials or subshrubs with a trailing, branching, and spreading habit, making them particularly well suited to hanging baskets in cultivation. Their leaves are typically small, succulent, and hard-surfaced, often reddish on the underside.
Flowers are notable for their fused petals and highly variable shape. Many cultivated species bear a prominent pouch on the lower surface with a small opening, giving the characteristic "goldfish" silhouette. Other species produce resupinate flowers — twisted 180° when fully open — which may be funnel-shaped and brightly coloured or white and bell-shaped. In nature, the nectar-filled flowers are pollinated by hummingbirds.
The genus was first described by the German botanist Heinrich Adolph Schrader in 1821. It is placed in the subfamily Gesnerioideae, tribe Gesnerieae, subtribe Columneinae, where it forms a clade with the related genera Codonanthe, Codonanthopsis, and Lesia.
Etymology
The name Nematanthus is derived from the Ancient Greek nema ("thread") and anthos ("flower"), alluding to the exceptionally long pedicels — up to 20 cm — of the type species, Nematanthus corticola, on which the flowers hang like pendants on threads. The genus was established by Heinrich Adolph Schrader in 1821.
Distribution
All species of Nematanthus are endemic to Brazil, where they grow primarily as epiphytes on tree trunks and branches in humid forest habitats, or in humus-rich crevices on rocks. No species is native outside Brazil.
Taxonomy Notes
Nematanthus is placed in the subfamily Gesnerioideae, tribe Gesnerieae, subtribe Columneinae within the family Gesneriaceae. Molecular studies position it in a clade together with Codonanthe, Codonanthopsis, and Lesia. The type species is Nematanthus corticola, originally described by Schrader in 1821; as of April 2021, Plants of the World Online recognised approximately 30 accepted species. GBIF lists 31 accepted descendants under the genus.
Cultivation
Nematanthus grow best at temperatures between 18 and 25 °C (64–77 °F); cooler temperatures of 15–17 °C promote a more compact habit. They require bright indirect light — direct sun causes leaf scorch. High humidity is preferred but plants adapt to typical household conditions. The tuberous roots retain moisture, so soil should remain evenly moist and well-drained; plants prefer being pot-bound and are more likely to bloom in that state. Under suitable conditions they can flower year-round. Regular pruning encourages fresh blooms. New plants are readily raised from stem cuttings.
