Nematanthus is a genus of approximately 30 species of plants from South America that are in the African violet family, Gesneriaceae. Some of these flowering plants are perennials, while others are shrubs. They are mostly epiphytic and grow on trees. These types of plants have spreading stems and are generally grown as hanging basket plants. Many species of Nematanthus were previously considered to be in the genus Hypocyrta.
One commonly grown species is Nematanthus gregarious, also known as Nematanthus radicans. This plant grows to a height of 2.5 ft (0.8 m) and a width of 3 ft (0.1 m). The branches are usually 1 foot (30 cm) long, trailing, and covered with small, oval leaves. The 1 inch (2.5 cm) long, orange flowers are pouch-shaped and have what appear to be a mouth, resembling a goldfish. Thus, this species is sometimes known as the goldfish plant.
Goldfish plants grow very well in warm, semi-tropical regions, such as Florida. The plants can suffer permanent damage if the temperature goes below 50°F (10°C) for six hours or more. The ideal temperature for growth is from 65-80°F (18.3-26.7°C). Nematanthus species can be grown as houseplants or in greenhouses.
It is important that the plants are in a humid environment. Grouping plants together can help to bring this about. Often, the plants are placed on rocks with water beneath them, or on slotted trays that hold water. If light conditions are appropriate, the plants can be grown in rooms that are humid, such as the bathroom or kitchen. One can also mist the plants regularly.
The care requirements of Nematanthus are fairly similar to those of African violets. They require diffused or filtered light to thrive, and can grow well under 14 to 16 hours of artificial light per day. Goldfish plants should not be subjected to direct sunlight.
Goldfish plants grow best if kept evenly moist. To achieve this, it is extremely important that their pots have good drainage, usually from a hole on the bottom, so that excess water can drain out. These types of plants should be treated with a complete fertilizer when the soil is wet. If they receive appropriate care, they can produce flowers all throughout the year.
Propagation is generally done from cuttings. Plants in the African violet family grow best with a special artificial potting mix that can be purchased at garden centers. It is usually a mixture of peat moss, sand, and perlite or vermiculite.