Some of the most exquisite alpine plants are in the genus Dionysia. In early spring these cushion-forming plants are covered with flowers and are displayed in the Davies Alpine House.
One way that alpine plants can cope with their harsh mountain environment is to form a low mound or cushion, hugging the stony ground or clinging to cliffs. This shape exposes the minimum surface area to the high winds and freezing conditions. The genus Dionysia has some of the most striking examples of this type of growth habit and when they flower in early spring, these plants are covered with tiny blooms. You can see them now in the Davies Alpine House.
Dionysias on display in the Davies Alpine House
Dionysias come from Central Asia, especially Iran and Afghanistan. The cushions are made up of hundreds of tiny leaf rosettes and each one can produce a single flower. Individual flowers look like miniature primroses so it is not surprising that Dionysia is very closely related to the genus Primula.
Left, Dionysia mozaffarianii, and right, D. michauxii.
Dionysias can be hard to keep alive in cultivation. They do not like too much water, especially in autumn and winter, and can easily rot away if there is not enough air movement around them. We grow them in a free-draining soil, incorporating plenty of 3 - 5mm grit (up to 50% by volume) to make sure excess water drains away quickly. The pots are kept in a cold glasshouse in the Alpine Nursery, to keep off the rain. They also like plenty of sunshine so our damp, dull winters are not ideal. To keep the collection going we have to regularly propagate our plants by taking cuttings. Each cutting is a cluster of leaf rosettes joined together by a thin stem. It is inserted into a pot of sandy soil in spring once flowering is over. After a few months they should have produced enough roots to pot them on.
Left, Dionysia cuttings ready to pot on, and right, young plants already flowering.
Young plants are potted on as they grow, into ever wider pots. A thick mulch of grit is used to keep the leaves away from the damp soil surface. Eventually you may be lucky to have a specimen so covered in flowers you cannot see the leaves. The last photo is of a Dionysia hybrid, a cross between D. curviflora and D. tapetodes. Many other Dionysia hybrids have been produced by alpine gardeners around the world, who are all striving to produce that perfect plant.
A Dionysia hybrid covered in flowers.
- Richard -
Several people contribute to the Alpine and Rock Garden Team blog. Richard Wilford is the Collections Manager in the Hardy Display Section at Kew. His responsibilities include all the areas where alpines are grown at Kew Gardens. The three team leaders, Joanne Everson, Graham Walters and Katie Price, each have their own particular parts of the Gardens to look after. Between them, these four experts have over 55 years experience of growing alpines.
Alpines at Kew Gardens are not only grown to create colourful and informative displays, they also play an important role in the research Kew carries out around plant naming, classification, biodiversity and conservation.
Mountains are found on every continent and each range has its own unique alpine flora, but these plants are under threat from climate change. As temperatures rise, alpines are forced higher and will eventually have nowhere to go. The alpine collections at Kew are studied to help us all understand the mountain flora better and make informed decisions about protecting its future.
"Probably the most beautiful glasshouse in the world is the Davies Alpine House at the Royal Botanic Gardens Kew", John Hoyland, Gardens Illustrated, April 2011
Richard Wilford has written a book on alpines, 'Alpines from Mountain to Garden', published by Kew Publishing. You can buy it in the Kew shops or from Kewbooks.com.
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