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All About Mossy Saxifrages

May 26, 2020
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Mossy saxifrages range from easy beginner alpines to Farrer medal winning specials! Find out all about them with John Richards’ latest article.

It’s a strange thing about mossy saxifrages.

They have all the attributes of ideal rock garden plants, being easy to propagate, easy to grow, floriferous, long-flowering, attractive and with enough species and varieties to satisfy the most ardent collector, and yet…….. Somehow, mossy saxifrages have, with the odd exception, managed to remain Cinderella plants for more than a century. Why should this be?

Well, whatever else you say about alpine gardeners, most of us are plant snobs, whether we admit to it or not.

The problem with mossy saxifrages is that some of them, mostly colourful hybrids such as ‘Peter Pan’, Pixie’, ‘Red Admiral’, ‘Winston Churchill’ (and there are many, many other hybrids) romp over rockeries and borders of small front gardens and, dare one say it, are undeniably ‘common’, whether the ‘c’ is spelt with an upper case or a lower!

Easy Mossy Saxifrages

Nevertheless, if one is looking for attractive cushion-forming plants which cover the ground, and themselves with flower, within a year of planting, one needs to look no further.  Some of the mossy saxifrage species will do this for you equally well, and I shall start by mentioning a few.

(For the cognoscenti, don’t give up! The charm of mossy saxifrages is that some are superb show plants, and others rare in cultivation and difficult to grow).

In my experience here in the north-east of England, the ‘easy’ species really are very easy. To propagate them, just tear out a tuft from the side of a cushion (reaching well down to make sure you have some stem), and then just tuck it in to any well-drained soil at the same depth, making sure that it doesn’t dry out for the next few weeks. And it will grow away!

Saxifraga rosacea (Irish Saxifrage)

The earliest of my ‘easy’ species to flower is the Irish (and French) native Saxifraga rosacea. In the wild, this grows principally on limestone pavements, for instance in the Burren and Cevennes. It is neat, with creamy-white flowers, and spreads in a fairly discreet manner. The cushion shown is about seven years old.

Saxifraga Pedemontana

Another early flowerer (from mid-April) came as a Turkish form of Saxifraga pedemontana. S. pedemontana is a very widespread mossy saxifrage species. It has different subspecies in the Cevennes, south-west Alps, Morocco, Corsica and Sardinia, Bulgaria and Romania.

It is not recorded from Turkey, but does occur in the Ukraine. In fact, it is likely that most forms of S. pedemontana are good garden plants, although the spectacular subspecies demnatensis from Morocco is now at best very rare in cultivation and may not be very hardy.

Whatever, my ‘Turkish plant’ grows all over my home-made tufa hump and seeds around in a modest way.

I also used to grow Saxifraga pedemontana subsp. cervicornis from Corsica and Sardinia, but this proved less hardy and disappeared after a hard winter.

The French form of this mossy saxifrage, which I have seen at Mont Cenis, is less attractive.

Mossy Saxifrages from Spain

Unlike the last two, most mossy saxifrage species originate from Spain, and more than 30 species grow there, many localised to just a single mountain.

One of the most straightforward in cultivation is Saxifraga vayredana. In the wild, this is only found on the Sierra de Monseny, north-east of Barcelona. Originally, I grew it planted out in a lump of tufa in the alpine house, but although I still have a plant there, it has proved easy to propagate and grow outside, particularly in my sand-bed.

It is late-flowering, from the end of May and into June most years. Out of flower, as in this photo, I find it very similar to Saxifraga exarata, which flowers at the same time, and both form rather yellowish-green cushions sticky with glandular hairs, but the leaves have a sweetly resinous scent, and unlike S. exarata they have no grooves above.

Saxifraga exarata itself thrives outside and has come to dominate one large trough  plagued by ants, which it seems to tolerate.

This is a widespread species from the Pyrenees to northern Greece and is very variable. Some forms have small yellowish flowers, but in plant grown here they are cup-shaped and white.

Perhaps the least attractive of the species grown outside is S. canaliculata, from the Cantabrian mountains of north-west Spain.

This is rather sprawling in habit, although it does have quite attractive leaves. The flowers are lax, but quite appealing when fully open.

Much more interesting is Saxifraga continentalis from north-west Spain and south-central France. In the wild this covers shaded limestone rocks with very little soil, and as these habitats dry out in summer, the plant completely disappears, to reappear again in the autumn.

It behaves in exactly the same way in my garden. Originally planted in a stony scree, it quickly migrated to a flat limestone boulder where it comes and goes in an apparently soil-free medium.

It is a close relative of our native mossy saxifrage Saxifraga hypnoides, but more compact and attractive.

Difficult Mossy Saxifrages

I now come to two species which are less than straightforward in cultivation, but which I can only grow outside, without cover. Saxifraga cespitosa is a very rare British native, from a few sites in Snowdonia and the Scottish Highlands (including Ben Nevis).

At one stage, a single capsule taken under licence from one of the last Welsh plants yielded hundreds of plants at the University of Liverpool gardens, Ness, and many were planted out in the original habitats where I stumbled upon a few, many years ago. Sadly, it is now once again as rare there as it was formerly.

This subarctic species ranges through northern Scandinavia to Iceland, Greenland and Labrador, as well was down the mountains of north America as far as Colorado. I believe it is a Labrador form that has entered cultivation and I have found quite amenable in a trough, although it is very slow and has not grown much.

We now come to a real star and my favourite mossy saxifrage. Saxifrage cebennensis comes only from the Cevennes in south-central France. It forms very tight sticky little cushions with charming white flowers with darker lines, yellow nectaries and red anthers.

I struggled with it in the alpine house, but when propagated and tucked into or under tufa in troughs it has thrived. Because it is the tiniest of species, I have found it to be an ideal inhabitant of a miniature garden I am developing.

Saxifrages for the Alpine House

Saxifraga cebennensis has been confused with the Pyrenean Saxifraga pubescens, but the latter is a much faster grower, at least under glass, where it has become a firm favourite of the Exhibitor, and winner of many Farrer medals, usually in the clone ‘Snowflake’.

I have never tried it outside, but having seen it in the wild in the Pyrenees, at Nuria where it keeps company with Androsace vandellii, I would be surprised if it would succeed.

However, I have found it straightforward in a very gritty mix in a plastic pot plunged in the alpine house, where my cushion has now reached some 20 cm in diameter.

This is indeed the alpine house plant par excellence.

However, S. pubescens and S. vayredana are by no means the only mossy saxifrages I grow under glass. In the mountains of the south of Spain grow a series of species adapted to dormancy during the hot summers there, but unlike S. continentalis, they form tight, rootless, silvery buds.

I have Mark Childerhouse, an enthusiast for all things saxifragaceous, to thank for Saxifraga erioblasta. This is one of several southern relatives I have seen in their Andalucian haunts, where it grows on the band of limestone which is crossed by the northern approach to the Sierra Nevada from Granada.

Others include S. globulifera from similar habitats around Ronda and Ubrique, and S. reuteriana from Grazalema.

I grow S. erioblasta planted out in the alpine house, in a mix composed largely of sand and home-made tufa, and in the partial shade of a large lump of the tufa.

It is a tiny plant, but knowing its native habitat, one suspects it is not that easy to grow, and I am delighted to have succeeded with it to the extent of not killing it, and producing a few flowers.

A fourth species grown under glass (so far) is another very local Spanish endemic, S. genesiana. Again, I have to thank Mark Childerhouse for the gift of this species.

Until recently, this was treated as a subspecies of the Pyrenean S. geranioides, but its only site, Sierra de Monseny, where S. vayredana also grows, is disjunct from the main range.

Like S. geranioides, with which I am familiar in the eastern Pyrenees, this is a large, handsome species with most attractive foliage. I may try it outside in the near future, where I would think it would appreciate a sheltered damp corner.

For a number of years I grew another species under glass. Saxifraga petraea comes from the Lake Garda area where it grows in shady, damp cliff sites in the Cima Tombaea area.

Years ago, a little collected seed thrived when planted out amongst the tufa under glass. It is monocarpic, but self-sowed so regularly that I did not have to worry about replacements. Then, as these things happen, one year no seedlings appeared and that was that!

Three Plant Stars

Space is limited to feature any of the many other stars which have featured during the last, lockdown month, but here are three.

In my admittedly biased view, Aubrieta glabrescens is not only one of the very best introductions from our 1999 AGS MESE seed collecting expedition, but for the alpine gardener it is the best Aubrieta. Like the best alpines, it is not easy to grow well, but is forgiving of mistakes. It originates from the summit of Smolikas, its only home.

Fritillaria pyrenaica is one of the latest to flower, and for some it is a good garden plant. I find it easier to grow in a pot, repotted annually after it has died down, and this year there were over 30 flowering stems.

Finally, Primula halleri arrived as a mistake, as someone is sending this our under various exotic names in the seed exchanges. However, it is proving soundly perennial and a good garden plant.

Image of John Richards John Richards

John Richards has lived in south Northumberland for 50 years and has been a keen grower of alpines, and visitor to the mountains, throughout the half-century. He and his wife Sheila have been in their present garden 30 years and John has been writing this diary about the garden since 2006.

John is Emeritus Professor of Botany at the University of Newcastle, where his research interests centre on the evolution and genetics of plant breeding systems. He is an authority on the genera Primula and Taraxacum (dandelions!). John is an AGS judge, exhibitor and Vice-President and previous President (2003-6).