Mexico, the Himalayas and tropical Africa, are some of the natural habitats of the plants of the Gesneriad family. Fortunately many of them adapt wonderfully to conditions quite different from those of their birthplace.
This mainly tropical family includes at least 126 genera of over 3000 species, and many more hybrids. The most familiar and widely sold gesneriad is the African violet, but many others deserve attention. If you already grow African violets you will be interested to know that some of these other plantsare quite at home to growwith them, while there are others that appreciate somewhat different conditions.
The forms of Gesneriad plants are varied, ranging from small ground-cover plants to shrubs and trees and include epiphytic and terrestrial species. The requirements of most are similar, and quite easy to provide. Potting mixes should be very well drained, yet moisture retentive. Watering needs to be regular, as most of these plants react badly to periods of drought. Gesneriads are mostly not gross feeders but need light applications of fertiliser regularly.
Almost all need good bright light, but not direct sun, which would possibly burn the leaves. Those plants whose light requirement is least are those which are most suitable as houseplants. This includes African violet, Streptocarpus, Columnea, Episcia and Sinningia (miniatures) and some other less well known plants. The tropical Gesneriads thrive when temperatures and humidity are fairly high, but some are hardy enough to survive a mild winter unaffected. In cold climates many will need winter protection.
These include the Columnea (sometimes known as goldfish plant), the Aeschynanthus (lipstick plant), Nematanthus and Codonanthe. Most of the others are hardy enough to spend all year round outdoors in sheltered locations in a warm climate.
The flowers of the Columnea are in blended colours of red to yellow. Aeschynanthus are normally orange or red. Nematanthus is brownish red red or orange and Codonanthe is white or palest yellow. Most have very long flowering periods and flower at different times of the year.
They should be tip-pruned regularly to promote branching. The cuttings so formed make excellent material for further propagation. Indeed, when a plant becomes old and woody, it is easy to start another one in this way.
A number of very showy gesneriads survive the cold season by retreating into dormancy, when the tops die down in response to cold or dry conditions. They should be kept almost dry whilst dormant. Under the surface of the soil you will find tubers or rhizomes, which then provide a start for the next seasons growth.
As soon as the tubers or rhizomes show signs of life in spring they should be potted into fresh potting mix then given a bright growing spot and adequate water. Depending on the variety, the time of this regrowth can be from June to November in Sydney conditions.
The principal tuberous gesneriads encountered are Sinningias. They can be varying sizes from miniatures like S. pusilla which is ideal indoors in a terrarium where it never goes dormant, to Sinningia speciosa (often known as Florist’s Gloxinia), which does well in glasshouse and shadehouse culture.
Achimenes, Kohlerias and Smithianthas form rhizomes when they go dormant. These rhizomes are underground structures some of which feel like grubs or pine cones. They should be potted up when just coming out of dormancy.
There are other useful plants in the family which do not fit into these categories. Some of these are Streptocarpus, Gesneria, Boea, Episcia, Chirita and Saintpaulia (African violet). Successful culture for them depends partly upon watering techniques as Gesnerias are particularly sensitive to drying out, and Chirita and African violets can easily be rotted by too much water.
Some of these Gesneriads are already well known pot plants; others deserve to be. Try some - to grow them is to appreciate their versatility and beauty.
These plants are natives of South Africa and grow well in the Sydney climate both outdoors and in indoor well-lit positions. The rosette-forming strap-leafed types have many large flowers produced over a long period in the warm months of the year. In colder outdoor conditions they do not normally flower in winter, and the leaves may become yellow and die off at that time. Repotting in spring generally initiates new growth and flowering. Very hot days, especially with low humidity may severely damage flowers, so keep the plant in cool conditions in summer. The branching, bushy Streptocarpus require similar conditions and are even easier to grow and flower.
Always use a very well drained potting mix, and avoid letting the plant dry out, especially during the growing season. A balanced liquid fertiliser will help produce a healthy plant with plentiful flowers.
Propagation is either from leaf cuttings, by division of the plant when repotting, by tip cutting of the shrubby types, or by seed. Hybrid cultivars do not reproduce "true" from seed, but germination is good and an interesting mix of colours can usually be expected.
Some of the most colourful plants in the Gesneriad family are seasonal, dying down in winter when they form scaly rhizomes under the soil. Growth starts again in spring when the rhizomes should be repotted. Place them on their sides and cover with a layer of potting mix. As a guide, plant 6-8 Achimenes or Eucodonias in a 15cm pot, but only 1-2 Kohlerias or Smithianthas.
These plants are not particularly fussy about potting mix, although it should be sufficiently well drained not to rot the rhizomes. Light fertilising and regular watering will encourage good growth. Bright light produces heavy flowering, so the plants are more satisfactory in outdoor positions of light, high shade, or in glass or shade houses. Flowers may be damaged by very high temperatures or low humidity, especially in the case of Achimenes.
Winter temperatures are fairly unimportant as the plants are dormant at that time. Keep almost dry in winter, and in cold regions do not allow the pots to freeze. Strong healthy growth the previous summer will produce numerous rhizomes to replant the following spring, this being the easiest method of propagation.
These heat loving ground cover plants come from Central America. They are usually grown for their beautiful foliage, although they do have flowers. These are small and not long lasting although they are produced in a constant succession in hot humid conditions. Flower colour is mostly red/orange, although some have yellow, lavender or pink flowers. It is important to keep them warm in winter as they will not survive in cold. In Sydney they will need to be grown indoors or in a glasshouse in winter. In summer they make ideal pot plants either indoors or outdoors in warm shady and protected locations.
Potting mix should be rich and well drained. In winter water sparingly, but not allow the plant to wilt. In summer, especially if grown outdoors, water regularly and fertilise with any fertiliser suitable for pot plants.
Growth is rosette like, but from the leaf axils are produced long stems each of which produce another rosette on the end. These (called stolons) can be cut off and rooted separately to produce more plants. A wide flat bowl is an ideal container and is soon covered with beautiful iridescent foliage. Episcias also are delightful hanging basket subjects.
The header photograph of this page is of Episcia 'Toy Silver' with its silvery leaves and tomato red flowers.
The wide variety of plants in the genus Sinningia ranges from very tall or bushy plants growing over a metre tall, to tiny miniatures.(See separate leaflet on Miniature Sinningias). The well known florists' Gloxinia is a Sinningia. Most Sinningias flower profusely in a wide assortment of colours, mostly in spring or summer.
The most obvious characteristic of Sinningias is that they grow from tubers. These are dormant in winter, when they should be kept fairly dry then be planted in early spring in pots of an appropriate size allowing 2-3 cm of potting mix around the tuber. Potting mix should be open and well drained to avoid rotting the tubers should they become too wet.
Bright light is usually necessary for sturdy compact plants and heavy flowering. A sheltered brightly lit outdoor position with high shade is ideal. Plants may be brought indoors for decoration when in flower.
Propagate using cuttings of surplus shoots removed from the tubers in spring. Rooted in a small pots of mix these will soon form tubers and usually flower in the second year, or by seed.
The pink flower towards the top of this page is a hybrid Sinningia speciosa. These are very popular pot plants and are frequently known as Florist's Gloxinia.
Many plants in the Gesneriad family are epiphytes, that is, in nature they grow perched on the branches of trees. They tend to have long trailing branches and are excellent for growing in hanging baskets and pots. The major genera in this category are Columnea, Aeschynanthus, Codonanthe and Nematanthus. Flowering varies according to genus and species.
Columnea needs a protected location as it is sensitive extreme heat and cold. Most of the others are more generally hardy. All suit both indoor and outdoor cultivation all year round, where they can be given bright light but little direct sun. Water regularly, but do not allow to remain flooded as their roots are not accustomed to excessive moisture. Regular fertiliser will help keep the foliage green and healthy and assist production of flowers, which may, according to species, be produced at any time of year.
Repot the plant every year. After flowering prune the trails to induce strong new growth. Cuttings (up to six per 15 cm pot) should be planted during spring or summer in an open, well-drained potting mix. Rooting is rapid, and can be followed by regular pinching to keep the plant compact.
These plants remain small and dainty, flower regularly and are good companions for African violets. They also require good light and humidity, with reasonable warmth. Potting medium should be very open and well drained, and watering is best if regular and even, preferably by wicking. Should extra shoots appear from the base of the plant they can be encouraged, and will eventually take over from the older shoot which may degenerate and can be removed. Propagation is from leaves, seed, or from tip cuttings.
In contrast to African violets, Sinningias have underground tubers. Dormancy sometimes occurs in response to cold or dry conditions. Keep the pot almost dry but warm until growth once again begins. Repotting can be carried out at this stage. Usually pots of 50-75 mm are best for miniatures. Very miniature cultivars thrive best in terrariums.
The Association holds meetings of its Gesneriad Study Group four times per year in the homes of some of its participants. All members are welcome to come to these. Definitely the place for members to learn about growing these great plants. And to actually acquire some of them!