Columnea is the genus of a group of plants, often called goldfish plants, in the gesneriaceae family. These types of plants can range in style from vining plants to small shrubs or trees. These relatives of the African violet are tropical or subtropical plants that are often found gracing trees in the tropics of Central and South America, though they also can be found in more temperate regions. Columneas are epiphytes, or air plants, that take much of their moisture and nutrients from the air. Though they aren’t parasites, they often rely on other plants — such as the trees in tropical jungles — to provide them with an area to grow on.
The foliage of the columnea is usually dark green with up to 3-inch, egg-shaped leaves and some fuzz. Flowers grow both singly and in clusters with colors including reds, yellows and oranges. The blooms’ petals give the flower a unique shape, with two petals forming a top covering and two rising — one on either side — to resemble a flying fish. It's this shape that gives columnea it's colloquial name — a goldfish plant. Their hanging or trailing nature makes them ideally suited for hanging baskets, though they also work well as groundcover under the proper conditions.
Columnea prefer plenty of bright to moderate light, whether from a window or from artificial light, and well-draining soil. The plants can tolerate some drought, though they prefer even moisture levels. Cool temperatures can be tolerated if the columnea is planted indoors and sits in a window, and underwatering is preferable to overwatering in cool conditions. Less water also is preferable during the plant’s non-blooming periods. Certain columnea species and hybrids require cool night temperatures to bloom, though most prefer warmer conditions.
There is some debate about whether all columnea fit under one general category or if they would fit better if subdivided into one of five categories: bucinellina, columnea, dalbergaria, pentadenia and trichantha. Both sides of the argument have high-profile botanists taking up the fight. A strong argument for consolidation is the simplicity of having every species fall under a single heading. A strong argument for subcategories is that no single characteristic accurately describes all of the 200-plus plants labeled as a columnea.