Alpine and Rock Garden team blog
The Alpine and Rock Garden team looks after a fantastic range of plants from the world’s mountain ranges. This blog includes stories about individual plants, growing techniques and trips to see alpine plants in the wild. You can visit plants from Kew's collection of alpines in the Davies Alpine House, the Rock Garden and Woodland Garden and read this blog to find out how the team gets to grips with cultivating them.
The eight months preceding the opening of the Davies Alpine House in 2006 was a period of frenetic activity. Rockwork was constructed, the beds filled with soil, plants planted and the whole glasshouse cleaned and tidied for the official opening on 11 March. The first photograph below shows the Alpine House in August 2005, when the rockwork had been built been but before any soil or plants had been put in. Around the sides you can see the black pipes that come up from the underground chamber, where air is cooled before entering the glasshouse. These pipes were later cut down to fit in the landscape and fitted with stainless steel bends to direct the cool air over the plants.
The Davies Alpine House in August 2005
There have been plenty of changes over the last five years, with improvements to the plant displays, new rockwork built and the addition of extra features to show different ways of growing alpine plants. More sandstone rocks have been added to provide additional nooks and crannies for alpines, and we have also built a wall of tufa. Tufa is a type of limestone, formed when deposits from water saturated with calcium carbonate build up to make a soft rock filled with tiny holes. Alpines can be planted directly into the rock where the roots work their way through the crumbly texture to find moisture, while the upper part of the plant is kept dry - just what many alpines like. The two photos below show the same area before and after the addition of the tufa, which was recycled from an old garden.
Top, the west side of the Alpine House in May 2006, and bottom, in March 2011
The next two photos show how the tufa and additional sandstone rocks have made a more interesting landscape and fully utilised the height of the surrounding walls:
Left, May 2006, and right, March 2011
Another new feature in the glasshouse is the construction of two dry stone walls, like cairns, to show another way of growing alpines. Plants are grown between the stone pieces, which have soil behind for the roots to reach into. One of these cairns is shown here, with the yellow Verbascum dumulosum in front, which flowers in May.
Stone cairn for growing alpines, in May 2010
The plants in the Alpine House have responded well to their new environment, especially the improved ventilation, the cooler summer temperatures and the higher light levels than in the previous alpine house, all essential for successful alpine cultivation. This is well illustrated by the next two photos showing the cushion plant Draba rigida. It was planted in 2006 between sandstone rocks on a vertical cliff. The first photo is from 2007 and the second from 2011, showing how well it has done. The high light levels inside the glasshouse have ensured the characteristic cushion shape has been maintained.
Left, Draba rigida in 2007, and right, flowering this week.
There are currently 443 accessions permanently planted in the Alpine House landscape and these are joined by the constantly changing displays of up to 100 additional plants brought in from the Alpine Nursery when in flower. Whatever the time of year, there is always something worth seeing
General view of the Davies Alpine House, March 2011
I hope this has given you an idea of how the Davies Alpine House has evolved over the five years since it opened. If you haven't visited recently then now is the time to come along to Kew Gardens and see how it has changed for yourself - over the next couple of months the display of plants will reach its peak.
- Richard -
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The native habitat of Tecophilaea cyanocrocus is the high Andes, where it grows on dry stony slopes from around 2000 to 3000 m altitude. In the wild it flowers in the Southern Hemisphere in spring, from October to November, and here in the UK from February into March. It immediately catches your eye in the Davies Alpine House with its amazing, deep blue flowers.
Tecophilaea cyanocrocus in the Davies Alpine House
With its crocus-like flowers it soon became known as the Chilean blue crocus although this plant is not actually a crocus but in a completely different family, Tecophilaeaceae. As well as the true species, two cultivars are also grown at Kew: Tecophilaea cyanocrocus 'Violacea' has flowers of a slightly more purple hue and T. cyanocrocus 'Leichtlinii' has more white in its petals.
Left, T. cyancocrocus 'Violacea', and right, T. cyanocrocus 'Leichtlinii'
We grow this eye-catching plant in pots in the Alpine Nursery but there are also some growing outside on the Rock Garden. Early each spring pots from the nursery are displayed in the Davies Alpine House.
Cultivation is quite straightforward. We use a free-draining compost and re-pot the corms each year in August. After re-potting, we plunge the pots in a sand bed, and water both the pots and the sand. The sand is kept damp until the corms come into growth, when we water them freely. Watering is eased off as the plants die back for their summer rest. During this resting period, the pots are sprayed over about once a fortnight, as they don't like to be dried out completely.
We keep the pots in a glasshouse to protect them from hard frosts but they will often survive outside in milder parts of the country, as long as they don't get too wet in the summer.
Pots of Tecophilaea cyanocrocus in the sand plunge in the Alpine Nursery
Propagation is mostly by corm offsets, though occasionally we will sow seed in spring. Seedlings are left undisturbed in the seed pots for about three years. This means that when we come to separate them and put them into bigger pots, they have already formed a small corm, which is less likely to suffer damage during repotting. After about five years they should flower and dazzle you with their electrifying blooms.
- Sue -
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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 -
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The Rock Garden at Kew is built with Sussex sandstone and although in recent years there has been a lot of new construction, especially around the Davies Alpine House; some parts of the Rock Garden haven't been touched since the 1950s. Over time the rocks settle, the gaps between them widen letting the soil fall through and in the worst cases the rock can become unstable. The following picture shows some older rockwork, where you can clearly see how the rocks have moved and eroded, becoming uneven and creating wide gaps.
Old rock work on the Rock Garden at Kew
Before we begin working on fixing the rock we have to propagate or move any plants we want to save, so we have something to put back once the work is completed. The next picture shows the area we are working on at the moment. Most of the rocks have been rolled back or taken away, leaving a bank of soil and just the lowest layer of rock exposed.
Rock removed to allow renovation work
The top surface of the lowest rock layer is then levelled using an electric power chisel to break away any lumps and a spirit level to ensure the resulting surface is level. Of course, all the correct safety gear has to be worn - steel toe-capped boots, gloves, ear defenders and goggles!
Chiselling the rock to create a level surface
The rocks are then carefully put back in position so that they fit tightly together. Even then there is more chiselling to do, this time by hand, to make them fit together exactly. This locks them into place and makes them very stable.
Left, a rock being moved back into place, and right, chiseling by hand to fit the rocks together
With a Rock Garden the size of the one at Kew, this work is ongoing and every winter we tackle a different area. It is a long process but worth doing well so the rocks stay in place for hopefully at least another 60 years.
- Joanne -
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Snowdrops are already flowering on the Rock Garden and one of the first to appear is a clump of Galanthus elwesii planted under an old Japanese maple. This species of snowdrop comes from south-east Europe, Turkey and the Caucasus and was named after the plant collector and traveller Henry Elwes in 1875. It is a strong plant, taller than the common snowdrop, Galanthus nivalis, and can have one or two green marks on the inner petals.
Galanthus elwesii on Kew's Rock Garden in early January
The marks on the inner petals vary in size and shape and sometimes they join together to make a fish-like shape.
Flower of Galanthus elwesii
Another form of Galanthus elwesii that is also on the Rock Garden is called 'Three Leaves'. Most snowdrops have two leaves, with the flower stem emerging from between them but as you can see in the next photo, Galanthus elwesii 'Three Leaves' has an extra leaf. This plant is also flowering now at Kew Gardens. There are 14 different species and subspecies of snowdrop growing on the Rock Garden and several cultivars, so over the next couple of months there should be plenty to see.
Galanthus elwesii 'Three Leaves'
Most snowdrops like plenty of sunshine, especially in the winter when days are so short, but in the summer they do not like to be too hot and dry, even though they are dormant, so plant them somewhere that has a little dappled shade once the leaves are on the trees or is shaded from the sun for part of the day, and avoid soil that becomes dry and dusty. You can plant the bulbs in the summer, but if they have been sitting on the garden centre shelves for a long time, they can dry out too much and not come up next winter. Buy them as soon as they appear in the shops and plant straight away. Alternatively buy them growing in pots at a spring flower show. This is the best way to find the more unusual forms.
A range of different snowdrops on display at the RHS February flower show in London.
Moving snowdrops 'in the green' means when they are still in growth, after flowering, so you can be sure they haven't dried out too much. However, digging them up before going dormant can damage the roots so it is best to keep them in some soil when moving them. If you are successful you can have a wonderful display once they become established in your garden.
- Richard -
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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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