Saxifrages by Tony Hale

Saxifrages are a large & important family of alpine plants. They grow mainly in the northern hemisphere in Europe, Asia, North America and the Arctic. There are over 400 species which vary widely and grow in many different habitats, so they have been grouped into fifteen distinct sections. However saxifrages from only three sections are generally found in common cultivation in gardens. These are :-

Porphyrion Section (the sub-divisions within this section are complicated and have been subject to changes in recent years so I shall just state that this section includes the Kabschia, Engleria & Oppositifolia groups of saxifrages that many of us grow & recognise).

Note: the up to date divisions within the saxifrage family can be further explored in Saxbase, the online database of the Saxifrage Society referred to at the end of this article.

Ligulatae Section (better known as the Encrusted or Silver saxifrages)

Saxifraga Section (known as the Mossy Saxifrages)

I shall refer to the common names of these groups by which most growers know them.

Kabschias, Englerias and Oppositifolia

The Kabschias are much admired in early spring for their neat and tidy cushions covered in flowers in shades of red, yellow, white or purple blossom. Typical species in cultivation are S. burseriana and S. marginata from Europe and S. lilacina from the Himalayas.

The Englerias have a more elegant appearance with their vertical flower stems in reddish-purple hues curved over at the top with pendant flowers in similar shades. Their foliage comprises silver or greyish rosettes somewhat similar to the Silver saxifrages. Examples of species grown are S. media from the Pyrenees and S. stribnyi from Greece.

'Allendale Elf' S. grisebachii

The Oppositifolia Group mainly comprise the different forms of Saxifraga oppositifolia which are widespread in the mountains of Europe, North America, Asia and the circumpolar Arctic Regions.

There has been so much hybridising within the Kabschia and Engleria groups by specialist growers over the last 100 years that there are now far more hybrids than species in cultivation. This has multiplied further since new desirable species from the Himalayas and Caucasus have more recently been brought into cultivation and used as parents of hybrids.

Typical hybrids grown by gardeners over the last 50 years include S. x apiculata 'Gregor Mendel', S x boydii 'Faldonside'. S. x irvingii 'Russell Vincent Prichard' and S. x anglica 'Winifred'. It should be noted that the name of the cross corresponds to the parents of the hybrid. For example in the above four cases, the name of the cross indicates that the parent species are as follows:-

x apiculata = S. marginata x S. sancta

x boydii = S. aretioides x S. burseriana

x irvingii = S. burseriana x S. lilacina

x anglica = S. aretioides x S. lilacina x S. media

Note that there were three parents in the anglica cross. This can be achieved by crossing an existing hybrid of two of the parent species with the third species.

The hybrid names such as Gregor Mendel and Faldonside are given because different cultivars can be achieved using the same parents in the same way that children in a family vary from each other with the same parents.

In the last twenty years, there has been a flurry of activity from hybridists both in the UK and in the Czech Republic. Most prominent in the UK have been the Kabschia hybrids raised by Raymond Fairbairn. With one or two exceptions, they have the prefix Allendale, the name of his home town in Northumberland. They now number more than seventy in total and for many of them, Ray like other modern hybridists, has used species which were not generally available in the earlier decades of the twentieth century. Species such as S. poluniniana, S. iranica, S. hypostoma, S. cinerea, S. georgei, S. dinnikii, S. columnaris, S. kotschyi, S. matta-florida, and S. lowndesii are now more widely distributed.

There has been similar activity in the Czech Republic over the same period, primarily from Karel Lang but with hybrids also from other growers including Jan Burgel and Dr. Maixner. Karel Lang has raised about fifty new hybrids, many named after famous painters and composers. Jan Burgel is best known for his hybrids in the 'Your' series such as 'Your Success' & 'Your Kiss' as well as those named after Stage & Film celebrities like Frank Sinatra and Marilyn Monroe.

Encrusted or Silver Saxifrages

Although there are only about ten species of silver saxifrages, there are many more hybrids and cultivars grown in gardens. They flower in June, later than the Kabschias, and erupt into clouds of pink, white & yellow blossom. They are much admired for the beauty of their silver or grey rosettes of foliage as well as the form of their flowers. They vary from the miniature rosettes and flowers of 'Minutifolia', which hug the rocks and screes to the huge, single rosettes of S. longifolia which build in size over a number of years up to 15cm in dia. before they erupt into a wonderful panicle of white flowers sometimes 60cm long. S. cotyledon and the longifolia hybrid 'Tumbling Waters' (below) can produce a similar dramatic effect. Other rewarding species but with multi-rosettes include callosa, cochlearis, hostii and paniculata. There are a number of choice hybrids and cultivars available which give a distinctive display on the rock garden including the following:

'Albertii', 'Baldensis', 'Emile Burnat' (= x burnatii), 'Canis-Dalmatica', 'Cecil Davies', 'Dr Clay', 'Esther', 'Frances Cade', 'Hirtifolia', 'Kathleen Pinsent', 'Monarch', 'Lantoscana Superba', 'Lutea', 'Minutifolia', 'Norvegica', 'Rainsley Seedling', 'Rosea', 'Southside Seedling', 'Tumbling Waters', 'Whitehill'.

Mossy Saxifrages

There are more than seventy Mossy Saxifrage species but only a minority are found in general cultivation due to their demanding requirements. Typically they have soft cushions or mats of evergreen rosettes. The flowers are usually white but sometimes cream, yellow or pink. Those mossy species which have given good results are grown in pots under cover with the following selection recommended:

S. pedemontana, S. vayredana, S. cebennensis, S. exarata inc. ssp moschata, S. pubescens inc. the cultivar 'Snowcap'.

Most mossies in cultivation are hybrids from a few selected species. They are easier to grow in the open garden and provide a rich display of colour in April and May including a range of red flowers. They prefer to be sited in semi-shade otherwise they are likely to scorch in midday summer sunshine.

The following are a recommended selection of mossy hybrids:

'Four Winds' (deep crimson, tall), 'Elf' (carmine, short), 'Gaiety' (pink, med. ht), 'White Pixie' white, short)

Cultivation of Saxifrages

All the above Saxifrages need similar conditions - very well drained soil in a moist, semi shaded site. Kabschias in particular will scorch if exposed to full sun in the middle of the day in the hot summer months. Some are more prone to this than others. It may be necessary to arrange shade netting over the plants as well as regular watering in hot weather. Saxifrages can be grown successfully in rockeries, raised beds, troughs, crevice gardens or pots, provided the criteria for shading & watering are fully met. In winter, saxifrages in pots are best grown under cover, either in glazed frames or in an alpine house to protect from the worst of the winter wet. They do not enjoy wet and cold conditions at the same time. Avoid hot, dry conditions in the alpine house in summer, when I find potted saxifrages are best outside in frames particularly if your alpine house is on the small side.

S. marginata 'Jaroslav Horny'

Website Links

The Saxifrage Society website has an excellent database named Saxbase where the species, hybrids and cultivars are fully listed together with details of their taxonomic relationships.

A large collection of images are shown.

www.saxifraga.org/plants/saxbase

Tony Hale

November 2009