Summer in the Alpine House

By: Richard Wilford - 03/08/2011


The main flowering season for alpine plants is spring, but there are many mountain plants that flower in summer. You can see plenty of these now in the Davies Alpine House. But why do they flower now?

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If you explore high enough altitudes in mountains such as the Alps and Pyrenees in July or August, you will reach elevations where summer has only just arrived. There you can find a range of alpine plants in bloom and meadows filled with colour. The following photograph was taken in the Caucasus Mountains of Georgia, in August, and shows a meadow above the treeline that was full of flowering plants, including Aquilegia, Campanula and the purple Geranium ibericum.

 

Alpine meadow in the Caucasus

An alpine meadow in the Caucasus Mountains of Georgia

 

When you grow alpine plants at low altitudes they often flower earlier than they would in their high mountain home, but if you give them enough water and keep them cool, many will keep blooming right into summer. The genus Campanula, the bell-flowers, contains many small, compact mountain plants that flower in summer. Two examples in the Davies Alpine House are Campanula fragilis and C. elatines, both from Italy. Campanula elatines, from the Cottian Alps of north-west Italy, is grown in crumbly tufa rock in the Alpine House because it needs perfect drainage and can easily rot in winter if it gets too wet. This plant flowers right through the summer months.

 

Campanula fragilis in flower Campanula elatines growing on tufa

Left, Campanula fragilis, and right, Campanula elatines

 

The only true summer-flowering Cyclamen is the European Cyclamen purpurascens. It comes from the Alps and further east into Slovakia and Hungary, and often grows in the dappled shade of woodland, in leafy soil among rocks. This species is found further north than other Cyclamen and is used to cooler summers and colder winters than other species, hence its summer growing season.

 

Deep pink flowers of Cyclamen purpurascens

Cyclamen purpurascens in the Davies Alpine House

 

In Turkey, summers are generally hot and dry but growing in limestone crevices in the Taurus Mountains, at altitudes as high as 2,400 m, is Pelargonium endlicherianum. This genus is mainly South African and most species are not hardy, but the habitats of P. endlicherianum can be freezing in winter and this species is hardy enough to survive alpine house conditions, where it too flowers all summer long.

 

Pelargonium endlicherianum flower  Pots of Pelargonium endlicherianum in the alpine house

Left, flowers of Pelargonium endlicherianum, and right, two colour forms on display

 

The Himalayan Mountains, especially the south-facing slopes, are subjected to the summer monsoon, which travels from east to west, dousing the hills and valleys with sometimes huge volumes of water. When the rains arrive the plants get growing, and summer is the flowering season for many Himalayan plants, including lilies, roscoeas and Incarvillea. Planted in the Alpine House is the trailing Incarvillea arguta, with pink flowers on stems a metre or more in length.

 

Pink Incarvillea arguta flowers

Incarvillea arguta, from the Himalaya

 

If you are lucky you may see the wonderful flowers of Tigridia pavonia in the Davies Alpine House. Each large flower only lasts a day and is best in the morning. This plant species comes from Guatemala and Mexico, where it is dormant in the dry winter months. It grows and flowers in summer when the rains arrive. Like all the plants mentioned here, it is climate that determines flowering time, whether it is the warmth of summer reaching the high Alps, the monsoon advancing along the Himalayan ranges, or the wet season arriving in Central America. It means we can keep the Alpine House looking good all summer long.

 

Yellow flower of Tigridia pavonia

Summer flowering Tigridia pavonia

 

- Richard -


2 comments on 'Summer in the Alpine House'

Peter Taggart says

22/09/2011 9:08:23 AM | Report abuse

Pelargonium endlicherianum was unscathed, frozen on a bench with me, at -15 to -18C last winter. (I did once kill it through drought in summer though) I would be glad to try quercetorum.


Dr. Tim Ingram says

24/07/2011 9:26:19 AM | Report abuse

Really interesting to see the Pelargonium. I have grown this well in the alpine house, where it flowered and set seed very reliably. I was tempted to try it outside on a sand bed but it has not been a success and must require the extra heat and protection under glass. Seedlings showed no variation in flower colour so it is fascinating to see the different forms at Kew. I do grow that other disjunct species, P. quercetorum, in the garden successfully, though it is shy-flowering.


About us

Looking north towards the Davies Alpine House from the Rock Garden

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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