Kent Alpine Gardener's Diary
This entry: 22 January 2016 by Tim Ingram
Temperate and Alpine Gesneriads.
Temperate and Alpine Gesneriads - talk to the East Kent Group of the AGS, 11th Dec. 2015
Ramonda and Haberlea are surprising but treasured plants grown by very many alpine gardeners. In a family - the Gesneriaceae - of generally tender and sup-tropical plants they introduce members from colder, often truly alpine and sub-alpine habitats, which yet retain the more exotic nature of the family as a whole.
Ray Drew has grown a remarkable variety of these plants for many years and written in detail about them in the Bulletin of the Alpine Garden Society Vol. 71, pp. 297-307, 2003. His talk to us brought together all of his experience of studying and cultivating these plants, more and more of which are being grown either in rock gardens or with minimal frost protection in the alpine house.
Ray has talked to us before on the family and began by looking closely at its botanical characteristics, particularly the form of the flowers and cymose inflorescense which delineates its members clearly (in most cases) from other closely related plants, such as members of the Scrophulariaceae and allied families. Horticulturally the Gesneriads are best known for the 'Cape Primrose' (Streptocarpus) and 'African Violet' (Saintpaulia), and other tender genera such as Columnea, Sinningia and the beautiful Episcia. What is surprising though is how many genera also grow in harsher climates, many of which (like the European Ramonda and Haberlea) are relict species resulting from previous glacial periods and isolation in mountainous regions. Ray's article in the AGS Bulletin is the very best place to learn about them in proper detail - and quite a few species are exhibited at the Alpine Shows - but apart from the familiar European plants I was surprised to learn how (relatively) cold hardy many other species are. A few, for example Tremacron aurantiacum and Mitraria coccinea can be grown in the garden given care, and many more with limited protection (often more from summer heat than winter cold). Very many are epiphytic or grow in fine crevices amongst rocks in cool shady aspects. In this way they resemble, and grow with, rock ferns and benefit from similar cultivation in well drained yet humus-rich medium. Like some ferns many alpine Gesneriads can tolerate periods of drought and restore full turgidity in their foliage with the onset of rains, so in cultivation they are better given less rather than more watering. Interestingly, again like the spores of xerophytic ferns, seed retains viability well even though it is incredibly fine and produced in huge abundance.
The list of genera in the family is fascinating: a wide variety of Petrocosmea species, grown especially for the symmetry of their rosettes of leaves as much as flowers; the Chinese genus Corallodiscus, often exceptionally beautiful in flower and leaf but a great challenge to grow; Briggsia, Lysionotus and Chirita - all occasionally seen at Alpine Shows; and of course the unrivalled Jancaea heldreichii of Mt. Olympus in Greece - though some of the Corallodiscus come close. Even in tufa this last species is tricky to grow in the UK but Ray showed a magnificent colony growing at Gothenberg Botanic Garden and Harry Jans famously grows it in his garden in Holland.
A fascinating family to learn more about in some detail and so well described and presented in Ray's talk to our Group.
(This picture is of the Farrer Medal winning plant of Haberlea at the East Anglia Alpine Show at Wymondham last summer):