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January 2008
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About Gesneriads

Many gesneriads bloom throughout the year, an especially welcome sight on a cold winter day. Whatever is a gesneriad? Almost all individual plants belong to larger plant families. In the case of the African violet whose botanical name is Saintpaulia, the larger family is the “Gesneriads” or Gesneriaceae in botanical Latin. Sometimes the relationship is made obvious by readily apparent similarities in the plant. For example, the Florist’s Gloxinia (properly called Sinningia speciosa) is also a gesneriad and bears a substantial outward resemblance to the African violet. There are many more and this outward resemblance is often not nearly so obvious. Most species are perennial herbs or subshrubs but a few are woody shrubs or small trees.
Some of the characteristics that help to determine whether or not a plant should belong to this family:
(1) The calyces are made up of four or five green or coloured, leaf-like parts called sepals. The sepals are separate; but sometimes they are united forming a cup or a tube.
(2) Inside the calyx is the corolla that is made up of five petals, or occasionally four, which are joined at the base forming a tube. The tube can be flat (as seen in Saintpaulia), elongated (as seen in Sinningia), or it can be two-lipped, consisting of upper and lower lobes of different sizes (as seen in Columnea).
(3) The ovaries are unicelled, enclosing a large number of ovules. It develops into a seedpod or a berry that contains tiny seeds.
(4) Normally there are two to four stamens in the flower, either fused in pairs or in a circle. There is a single pistil.
(5) The leaves are opposite and almost always simple and they may be in whorls of three or more at the same node. Sometimes the opposite leaves may be of unequal size as is well demonstrated in the genus Dalbergaria. The leaves may be green, variegated or they may be patterned with red or metallic hues, the latter is well demonstrated in the genus Episcia.
(6) Gesneriads may be herbs, shrubs, vines and even small trees. Most are terrestrial, but some like orchids, are epiphytes, which grow in the crutches of trees. In their natural habitat, gesneriads will be found growing in conditions ranging from mottled shade to full sun.
(7) The roots are fibrous, arising from the base of the aerial stem. Underground storage structures called rhizomes and tubers are sometimes produced.
The Gesneriaceae are widely distributed throughout the tropics of the world, with a number of species growing in temperate climates, especially at high altitudes in mountainous regions of Asia, Europe and South America. Among the more common varieties, Saintpaulia (African Violets) come from east Africa, especially Tanzania and Kenya. The Lipstick Plants (Aeschynanthus) are native to the Malaysian archipelago and nearby locations in south Asia. Sinningia species, including the Florist Gloxinia, come from Brazil, as does the Goldfish Plant (Nematanthus). The only Gesneriads growing in Europe are some species of Ramonda, semi-hardy alpines from the mountains in the south. These can be grown outside as far north as Scotland. A few relatively obscure species grow in Australia and New Zealand.
Some of the gesneriads grow naturally in moderately moist and shady conditions, with steady warmth. They are often comfortable in typical household conditions, and are good candidates for the new grower. Others grow at high altitudes, in the constant presence of cool mists, and require more specialized and constantly moist conditions. Still others grow on rocky slopes or cliffs, or high up in the rainforest canopy in small deposits of moss or leaf mold. They are adapted to occasional drought, and a grower must take care not to overwater.
This is a plant family of great diversity, and many grow under the same conditions we enjoy. Many of the easiest and most beautiful plants for the home or greenhouse belong to the gesneriad family. Some gesneriads go dormant for a short period of time. These are either tuberous or rhizomatous gesneriads.
Growing conditions:
(A) Columnea requires temperatures of 65 to 75 degrees Fahrenheit and bright reflected light. Keep the soil moist at all times, and provide humidity by placing the plant on a gravel-filled saucer (a humidity tray) or keeping it in a humid room such as a bathroom or the kitchen. These moisture-loving plants also appreciate a daily misting.
(B) The genus Episcia, or flame violet, includes six species of creeping evergreen tender perennials. Provide rich, fast-draining soil and plenty of humidity.
(C) Streptocarpus, or Cape primrose, requires care similar to that for the African violet but prefers more light and cooler temperatures (70 to 75 degrees).
Streptocarpus will grow happily in potting mix designed for African violets. Provide filtered bright light and a humidity tray. Don’t mist Streptocarpus. To encourage bloom, provide a high-phosphorus liquid fertilizer diluted to half strength every two weeks.
(D) Streptocarpella is a subgenus of Streptocarpus and requires the same care but blooms more profusely.
(E) African violets (Saintpaulia) require a south-facing exposure without direct sun. Repot annually, using a soilless mix designed for Saintpaulia; apply an African violet fertilizer regularly, according to package directions. These plants appreciate the use of a humidity tray. Cold water causes leaf spots, so if you’re watering from the top, make sure the water is warm.
(F) Sinningia grows from tubers and requires only moderate amounts of water until the roots are established. Keep the soil damp during the growing season, irrigating with tepid water. Sinningia requires bright reflected or filtered light and cool temperatures (60 degrees). Apply a high-phosphorus fertilizer once a month from the end of the plant’s flowering period until the foliage dies down.
(G) Gloxinia are now included in the genus Sinningia; they require the same care.
Provide bright light: an east- or northeast-facing window works well. Fluorescent lighting is beneficial too. If you use fluorescent bulbs, keep plants 6″ to 8″ from the fixture for 14 hours a day.

A great article that provides information is available at this link.

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