Geoffrey Charlesworth, author of The Gardener Obsessed and The Opiniated Gardener has written articles for several journals and newsletters for rock gardeners. He shares a garden in Massachusetts with Norman Singer where they grow Saxifrages and other plants.
We have a big garden in western Massachusetts with all kinds of growing conditions possible if you want to go to the trouble of clearing rough woodland and carving beds out of meadow. After 25 years we have arrived at a mixture of borders, woodland gardens, raised beds, and a lot of improvised planting areas and containers with various degrees of overhead protection and lack of it, exposure to all points of the compass and even a 'greenhouse'. The only thing we lack is an English type greenhouse with careful year-round care for show plants. Actually I am not at all interested in showing plants. Outside our local NARGS chapter meetings there are only a couple of shows in the whole of the country the size of Europe that one could even think of visiting. We use the chapter meetings for show and tell but rarely for competitive showing.
This absence of motive contributes to the faint interest anyone has in the US for growing a few difficult plants to perfection in pots on benches in greenhouses. All Americans get a kick out of the shows the English, Scots and Czechs put on and feel some dissatisfaction with their own efforts when they get home to their own common or garden plants. However there is quite a lot you can do in a garden and envy at other people's conditions soon vanishes when you get back to familiar surroundings and realise you can do some things moderately well. So I would like to describe some of the ways we grow saxifrages in western Mass.
I ought to start with the problem of actually getting hold of plants to grow. Unlike the UK there are only a few nurseries selling rock garden plants. In any given State you could only expect one or two at most and you have to remember that most States are as big as European countries. Buying saxifrages from a collection of plants displayed in neat rows is a luxury that is possible only on a rare visit to Grand Ridge nursery in Washington State or some such specialist nursery. There are a number of mail order nurseries (not a large number) that sell saxifrages and from these a collection can be built up slowly. This means Porpophyllums and Encrusted of course as hardly any of the other species can be found anywhere. Seed lists are a good way to get hold of species saxifrages and I belong to all the exchanges likely to have them. For instance, last winter I sowed about 40 sax. acquisitions, and since many take two years to germinate and almost three before you can transplant I always have a lot of pots around.
I have obtained most of my named Kabschias from Siskiyou nursery in Oregon and Rick Lupp's Mt Tahoma nursery with several coming by mail from the Czech Republic. The survival rate is better from Stateside nurseries because they can ship them in the growing medium, whereas the Czechs have to bareroot them and then they are not so easy to re-establish. This was true when I used to get plants sent from English nurseries either by mail or when visiting on vacation. I grow a vast number of things and need to have plants that don't demand too much coddling.
I have found that Porophyllum saxifrages will not thrive in full sun in our relatively hot summers. Mine are grown in raised shady or semi-shady beds with rather fast draining soil (coarse sand in the top layer) or in troughs also located in shady areas. They are near enough to a faucet so that I can water if necessary in droughty periods, but most of the time I don't water at all. It is difficult to generalise about climate but we do get something like 40 inches of rain a year, some of it in the form of an erratically deep snow cover. At some time in the summer we get a period of at least two weeks without rain so there are desperate weeks in most years. Saxifrages are less likely to mind drought than many other genera and less likely to mind cold than nearly any other genus (even fully exposed to weather they live through - 20'F with no problem).
I have tried mossy saxifrages in similar situations successfully, if you don't mind an occasional die back patch after flowering. Some of the mossies will stand full sun but I wouldn't now deliberately plant there, having lost several used as 'edging plants'. Silvers are willing too in full sun but they seem to grow best in much the same conditions as Porphyrions.
We have a number of woodland types (S. pensylvanica for instance) which can compete with the vigorous plants of the woods; a few species have even become weedy in some parts of the garden (S. virginiensis at one time), but mostly saxifrages are among the more precious of our plants. I dare say our collection of saxifrages is not very different from other gardeners' except for those gardeners whose main interest is in the alpine house. We have a fair number of Kabschia but nothing compared to the Czech giants (Karel Nemecek, Holenka, Lang and others). My favourites are not necessarily the newest but rather the ones that have grown into large mats; for instance the many relatives of x elisabethae and x apiculata which are such good growers. But we have a few of the modern treasures such as 'Golden Prague', 'Karel Capek' and 'Vladana'. I grow as many species as I can, mostly from seed, and particularly like S. ferdinandi-coburgi, S. stribrnyi and especially S. caucasica.
As for silvers, I have grown S. longifolia frequently from seed. Usually you get a hybrid even from seed from very good gardeners - assuming the true species makes offsets. I have grown plants from seed collected in Spain that had multiple rosettes. Occasionally a plant will behave as it should, send out a magnificent plume and then die. I have never had self-sowing from such a plant. I have had scraps of material called 'Southside Seedling' too but never the plant one sees pictured in books. The silvers self-sow with great gusto and as I grow several species together, none of the seedlings have reliable names. I leave them hoping to get a good hybrid out of the mess. It would be great to have a readable monograph for gardeners on identification of the Ligulatae section.
Linc Foster's garden was only half an hour from ours. He grew his saxifrages in an alpine house and in troughs close to the house. They didn't get winter cover. He also had some pieces of tufa stacked into a wall around the patio which grew saxifrages very well. He claimed he had no success with mossy saxifrages, but we find we can grow them well enough. The problem is to find enough space for the vigorous ones. The tiny wellbehaved hybrids like 'Peter Pan' fit, into a raised bed with the Kabschia, a large plant of S. trifurcata would overpower small buns. But it is still worth growing. The problem with mossies is the collection of nameless mounds you accumulate after a few years of seif-sowing.
Other favourites which don't fit into the "you-can-find-it-in -a-nursery" kind are bronchialis, exarata and retusa. In fact all the many forms of oppositifolia are worth growing and I try seed of any collection of oppositifolia itself. Some of them turn out to be quite good, amenable plants. Some plants are grown just for the mat or bun since the flowers are either unreliable or plain Janes when they finally arrive.
The garden is surrounded on three sides by State forest, so a good bit of wood cutting goes on sometimes. If we can pick-up a hollow log this can often be used as a container for saxifrages. A good way to close the ends is by building a miniature 'wall' to keep the soil from being washed out. Eventually the mats outgrow the space or the logs rot away, but the effect can be very pleasing for a time.
In late October, after the trees have dropped their leaves and before the first snow arrives, is a good time to enjoy saxifrages outside. The buns and mats are at their best; one Saxifraga longifolia, now 9 inches across, is magnificent, and the first buds are visible on the Kabschia. But whenever there is an open period during winter there is always something to admire in the raised beds, and we sometimes get a flower as early as March.