Toronto Master Gardener Factsheet    

The Gesneriad family of plants originate in tropical forests where they have adapted to relatively low levels of light and fairly constant moderate to warm temperatures. It is for this reason that most make good houseplants. A few of the gesneriads are familiar to most people. African Violets were among the first of the gesneriads to become popular. Gloxinia, hybrids of Sinningia speciosa, are as popular today as they were in the mid-19th century, their enormous, showy flowers providing a continual source of fascination for the plant lover. The gesneriads' range of plant habit and flower form is enormous, challenging in diversity that other family of predominantly tropical plants, the orchids. These 'other' gesneriads range in difficulty of culture from easy to challenging but fortunately most of our modern cultivars fall well towards the easy end of the spectrum.

Categories of gesneriads

There are three categories depending on the root structure of the plants.

• The tuberous rooted and rhizomatous plants are adapted to endure seasons of bad weather when the foliage dies back but the underground fleshy or woody roots sprout again when good weather returns.
• The fibrous rooted plants may be either annual or perennial but in either case are dead when the foliage dies back to the soil. This category contains many, perhaps most, of those plants which have potential for the home, including African violets.

Notable Cultivars

• The African genus Streptocarpus has long had hybrids available under the name 'Cape Primrose'. The commonly available Streptocarpus have fairly large, long and narrow leaves up to 30 cm in length which form an untidy rosette. From the base of these leaves arise flowering stalks several inches in length at the top of which are produced one to six very large showy flowers in a variety of colours. A well grown plant may have 50 flowers open at once. Good varieties to try are the 'Nymph' series: S. 'Constant Nymph', the original, has blue flowers with a yellow throat about 6 cm across. S. 'Maasen's White' has identical white flowers with a yellow throat. Other 'Nymph' mutants with larger flowers, smaller habit or different shades of blue are available. While Streptocarpus plants prefer fairly cool temperatures down to 55 degrees at night, they do tolerate normal house temperatures.
• The Episcias have colourful foliage and bright reddish orange flowers. Their natural range is from Mexico through Brazil where they often form a colourful groundcover in tropical forests. They love warmth and humidity and will not tolerate cold. Cultivars of the Episcias are innumerable. Noteworthy are the old favourite E. 'Acajou' with 8 - 10 cm leaves of silvery green and dark tan with many smallish red flowers, and the pink, green and white leaved E. 'Cleopatra'. The former is easy and floriferous, while the latter is quite difficult but very popular because of its most unusual foliage colours. E. dianthiflora and the hybrid E. 'Cygnet' have large fringed white flowers and plain green foliage and are more tolerant of cold than most. The former has small, dainty leaves, the latter bigger leaves and flowers with tiny purple spots. All Episcias produce stolons (runners, as in strawberry plants) and these must be limited in number if good flowering is to take place.
• S. canescens (formerly R. leucotricha) is a curious plant. New shoots sprout on short canes from what may grow to be an enormous ( 25 cm or more) largely above-ground tuber. The four leaves on top of the very hairy canes are covered with soft, silvery hairs. The visual and tactile effect is much like silver crushed velvet. From the centre of the four-leaf rosette grow many pink tubular flowers. S. eumorpha has shiny green leaves and large white nodding flowers, sometimes lined or flushed with lavender or yellow. This is not a difficult plant but it does go dormant.
• S. pusilla is one of the smallest flowering plants of horticultural importance. It may be grown and flowered in a thimble. With delicate lavender flowers held well above the foliage, it is a true miniature delight. It is also ever-blooming and will not go dormant unless forced to. S. 'White Sprite' is a pure white form of this species. Both require high humidity and do well in covered goblets or snifters.
• Pusilla and other similarly sized miniatures have been crossed with larger species to produce many miniature hybrids which have the everblooming habit of their smaller parent. These miniature Sinningias are very popular and are available in many colours. Most grow no larger than 15 cm in diameter, usually less. Some popular types are S. 'Dollbaby' with large nodding lavender flowers; S. 'Cindy-ella' which has purple upper lobes and white lower lobes with many purple spots running into the throat; A. 'Tinkerbells', a very reliable hybrid with many reddish purple tubular flowers produced on a taller growing plant than most; and S. 'Bright Eyes' which has darker and larger flowers than S. pusilla on a plant only slight larger (to 5 cm diameter).

Growing gesneriads

Soil

Any loose, well-drained soilless mix will do. A good quality African violet soil is quite good for such terrestrials as the Sinningias and the Streptocarpus and for the epiphytic genera (Columnea, Nematanthus, etc.). The latter will benefit from the superior drainage provided by the addition of 25% perlite or fir bark.

Fertilizing and Watering

With a growing medium that is low in actual soil, fertilize lightly with every watering. Use 1ž4 tsp of a balanced fertilizer such as 20:20:20 per 8 litres of water. Fertilize less often with a predominantly soil-based medium. Most gesneriads prefer even moisture, neither under or over watered. It is unwise to overpot gesneriads as excess soil, not penetrated by the roots of the plant, will stay wet and may result in rot.

Location

Almost any window will do but east, south or west exposures are best. Protect the plants from hot, direct sun in the summer. Some species such as Sinningia pusilla and many of the Gesneriads will thrive with much less light than most - these very low-light plants do, however, often require the high humidity of a terrarium.

Artificial Light

This is perhaps the best way of growing gesneriads in the house. An ordinary two-tube four-foot fluorescent fixture, available at hardware stores for $15 - $30, will do very well for most gesneriads. Use one each of cool white and warm white tubes. Special plant growth tubes are not necessary but some provide a more pleasing colour of light. Place the fixture so that the tubes are 15 - 30 cm above the foliage. Try to keep up the humidity around your plants, keep cold drafts away and enjoy the beauty resulting from your efforts!

 

Factsheets are produced by the Toronto Master Gardeners in association with the Toronto Botanical Garden. They provide introductory information about a broad range of horticultural topics and are intended for personal use and study purposes. Should your gardening group or organization wish to use multiple copies we ask that you inform the Toronto Botanical Garden at info@torontobotanicalgarden.ca.

Date revised: This factsheet was created prior to May 2005.