Tromsø Geophysical and Climatic facts.
Located at almost 70 degrees North, corresponding to a latitude similar to the North Shore of Alaska, Tromsø's location might invite thoughts of an extreme arctic climate. However, a branch of the Gulf Stream provides the coastal areas of Norway, including North Norway, with a moderating influence, giving rise to a climate which in Tromsø, with its proximity to the outer coastline, results in relatively mild winters (average January temperature being minus 4.4 degrees Centigrade) and relatively cool summers (average July temperature being plus 11.8 degrees Centigrade). Precipitation is moderate with a January average of 95 millimetres and a July average of 77 millimetres. However, there is great variation from year to year: the driest July during the last 30 years saw only 2 millimetres of rain, while the wettest had 175 millimetres. In this era of speculation about climatic changes, it might be of interest to note that the only meteorological parameter which has significantly changed over the last 30 years in Tromsø is accumulated depth of snow, showing that there have been fewer days of winter temperatures above freezing. This culminated in the winter of 1997 with a record 240cm of snow on the ground on May 1st. This, I hasten to add, is exceptional.
Inland, towards the Swedish border, far from the influence of the Gulf Stream and the North Atlantic, one finds a more "arctic" climate with much colder winters and warmer summers. Both on the coast and inland there are high mountains with a gradient towards more alpine conditions with increasing altitude.
The only truly "arctic" features of the climate in Tromsø are the two months of "darkness" from November 20 until January 20 (the sun being below the horizon all the time) and the two months of midnight sun from May 20 until July 20, when the sun never sets.
As to the growing season, Porphyrion Saxifrages flower in Tromsø from the end of May until mid or late June, depending on snow depth and the season. However, native Saxifraga oppositifolia has a head start and could bloom in bare spots from late April or early May on. Species and cultivars of section Saxifraga will bloom in last half of June, while plants in section Ligulatae will flower in July. The growing season for alpines can last until the end of September, and occasionally into October.
Brief History of Gardens in Tromsø
One of the earliest descriptions providing evidence for widespread interest in ornamental gardens in Tromsø dates from 1864 when the Swedish botanist T.M.Fries visited the town in the early spring. He wrote about his impressions in the following way: "Now, as early spring arrives, the number of species cultivated are not great, but large numbers of multicoloured auriculas are flowering wonderfully in the gardens in town". The introduction of new plants for cultivation in Europe, alpine and others, which increased dramatically during the first half of the 20th Century, provided a steady, if slow, influence on gardening in Tromsø resulting in plants such as Meconopsis betonicifolia being in cultivation here around 1950, about 25 years after its introduction to cultivation in Scotland and England.
More widespread interest in alpine gardening, including the cultivation of species of Saxifraga, developed slowly. Even today the number of gardeners with a keen interest in alpines in general and Saxifraga in particular is not large, with just a handful of people being seriously interested and knowledgeable. The most noteworthy of persons growing Saxifrages here is Ole P. Olsen in Balsfjord, just outside of Tromsø The opening of the Arctic-Alpine Botanic Garden in 1994, as well as Ole Olsen's enthusiasm, have created a climate for gardening where interest in and knowledge of alpines, including Saxifrages, have every chance of becoming more widespread.
Saxifrages in the wild above the Arctic Circle in Norway
This paper deals only with species growing in mainland Norway, thus excluding Svalbard/Spitsbergen and other high-arctic locations. Norway has a total of 18 species of Saxifrages growing in the wild. Fifteen of these are found above the Arctic Circle, and in the county of Troms. The most garden-worthy of these are: S. cotyledon; S. paniculata (both rare in North Norway); S. oppositifolia; S. aizoides; S. hirculus; S. cernua and S. cespitosa. In addition S. stellaris is quite beautiful, but its requirement for growing in very wet and cool places would make it an object for the extreme specialist. The other species would probably only be of interest to the collector who wants to see every species in the garden. They are: S. hieracifolia; S. nivalis; S. tenuis; S. foliolosa; S. adscendens; S. granulata and S. rivularis.
Focussing now on the species of garden value, S. cotyledon is rare in northern Norway, but still is found on several locations. It almost always grows in steep, rocky places. S. paniculata is rare in the extreme, being found in only two locations above the Arctic Circle. (It is then found again in a restricted area on the West Coast of southern Norway). It usually grows in rocky, steep places, but on the two locations in North Norway they are found on well drained flatter ground. Both are fairly widespread in cultivation, but often introduced to gardens from other populations than the wild Norwegian ones.
S. oppositifolia is widespread in North Norway, and fairly common on limestone. One curious consequence of the cold climate is that this, and many other alpines, can be found growing all the way down to the shoreline. It is a wonderful sight indeed, strolling along some limestone shoreline on a bleak, cold day in May, snow covering the mountain, waves rolling in black and forbidding, breaking against the rocks, and then: the sparkling pink jewels of flowering rødsildre (red saxifrage) as the Norwegians call S. oppositifolia.
The most widespread of all saxifrages in Troms, S. aizoides, is also pretty to behold, although maybe not of the same breathtaking appearance as its pink sister above. It blooms much later, in July and into August, growing in moist, gravelly places and not minding more acid ground. Each flower, despite its small petals, is quite beautiful, but the most impressive thing about the "yellow" saxifrage is its sometimes numerous and very large mats being covered with flowers. A wonderful sight that is made even more striking by the fact that the various plants can have shadings of colour starting from lemon yellow through nuances of bronze all the way to coppery red. It is an easy plant in the cool garden.
In Greenland a natural hybrid between S. oppositifolia and S. aizoides occurs. This plant, S. nathorstii, stabilized through a doubling of chromosomes, comes true from seed, thus constituting a new species. It is one of the more interesting plants in the Botanic Garden in Tromsø This hybrid has never been found in Norway. This is understandable since the two species flower at very different times, and although occasional hybrids may form, another rare event of doubling of chromosome numbers may be needed for stabilization to occur.
Rare and very beautiful is the "marsh" saxifrage, S. hirculus. This again is a very elusive species in Norway being found only in the two northernmost counties of Troms and Finnmark. It is, however, a circumpolar plant and thus found again to the north and east of Norway. From low cushions of dark green, small leaves, the flower spike rises 10-15 cm, carrying relatively large, butter-yellow flowers. It is a good garden plant with us. Its close relative from Svalbard, Saxifraga flagellaris, has the added attraction of red stolons.
S. cernua is a common mountain plant in wet, cool, gravelly places throughout Norway. Not a great beauty it still is a charmer with its good sized white flowers on top a short, wiry stem, and the striking reddish propagules in the leaf axils.
The last of the wildlings I chose to include is again a most beautiful plant: S. cespitosa, of the section Saxifraga, grows only on limestone. Low, neat mats of green leaves, attractive in themselves, support masses of white to cream, fair size flowers on short stems. Being a variable plant in nature, one should look for the better forms for cultivation in gardens and bring cuttings of this not too common plant home if desired. This is also a circumpolar species.
Saxifrages cultivated in private gardens until 1985
Only two groups of saxifrages were really common in gardens around Tromsø until quite recently. These are first the S. x arendsii type hybrids. A number of these are commonly grown and generally do very well in our cool and not too dry, sometimes wet, climate. There has not been much focussed interest on the various forms and cultivars in the sense that no-one I know of has been collecting named varieties. That may change now since there seem to be an international renewed interest in these plants. In particular, the Arctic-Alpine Botanic Garden in Tromsø will soon be able to show about 40 different, named cultivars thanks to the support of Peter Smith. This collection should inspire much interest.
The other species commonly grown would be S. umbrosa and related species and hybrids. S. umbrosa itself is in fact an "old" garden plant in the region as documented material from before 1900 exists. While saxifrages, with the exception of S. umbrosa, had not been staple plants in gardens around Tromsø in the early days of the 20th Century, it is interesting to note that even 100 years ago the really interested gardener here had a number of species growing. Thus the pharmacist P. Svendsen around 1900 lists the following plants from his garden: S. aizoon (probably S. paniculata), S. altissima (S. hostii), S. Andrewsii (S. x andrewsii), S. cespitosa, S. cotyledon, S. cuneifolia, S. Ehrenbergii var. palmata (which I have not been able to identify as to correct name), S. x geum, S. hypnoides, S. rotundifolia, S. sponhemica (S. rosacea) and S. umbrosa. (I am indebted to Professor Brynhild Mørkved of the Dept. of Botany, Tromsø Museum, for this information).
Saxifrages cultivated in private gardens after 1985
This division in the treatment of Saxifraga cultivation in Tromsø may seem artificial, but there really is a division around 1985, due to one person. Ole P. Olsen in Balsfjord, just outside Tromsø had been a plantsman since the 1960s when he worked in the nursery of Bjørk? in Tromsø From around 1970 he started his own garden at Slettmo in Balsfjord and around 1985 he became aware of the "Kabschia" saxifrages and placed his first order with Sündermann in 1986. Since then Ole has been a great spokesman and inspiration for growing the choicer saxifrages within the Porphyrion and Ligulatae sections, in particular. As many of the participants at the Seminar "Saxifrages 2000", and the readers of this article, will know, he has built an extensive international network and is justly famous in his own region and country for his contribution to horticulture, and specifically to growing saxifrages.
Presently many gardeners cultivate Porphyrion saxifrages, but most do it as a "side dish" and no one specializes to the extent that they grow only saxifrages. However, the few that are captured by the charm and spell of these plants and then concentrate on giving them an appropriate "home", will find that the climate in Tromsø is quite good for the successful cultivation of a number of species and hybrids.
Conditions for cultivativation of Saxifrages in Tromsø
This discussion will focus on the three sections of major importance for alpine gardening: Saxifraga, Ligulatae and Porphyrion. I will also list examples of assorted plants from other sections which have proved hardy and good.
One thing should be made clear at the outset: cultivation in pots and in alpine house is non-existent in Tromsø. Every grower cultivates their plants in the open garden without any protection whatsoever. Every observation made on success or failure therefore refer to this situation.
First some general observations on the climate and the growing season in Tromsø. Starting with winter, we generally have a good snow cover from October-November on, until the middle of May. However, due to the proximity to the North Atlantic Ocean and the influence of the Gulf Stream we can, and usually do, experience mild periods during the winter with melting snow, rain and subsequent ice formation. This is of course less than ideal, yet many plants endure without adverse effect. The exception will be plants which can not tolerate wet winter conditions. Typical examples would be Dionysia spp. and Primula allionii and, one suspects, saxifrages such as S. lilacina. When snow finally disappears at the end of May we have one blessing in Tromsø after the snow is gone and the ground is bare, we almost never have frost which could damage early flowers. At that time the midnight sun is already in the sky, and although it can be cold, it almost never freezes. The summer is unpredictable. It could be grey, it could be sunny, it could be wet or it could be dry. But one thing is (almost) always true: the temperature will be on the moderate to cool side, thus causing very little heat and water stress to the plants. This may be one of the major reasons why so many saxifrages are doing quite well here.
In section Saxifraga there are relatively few species grown in gardens, but correspondingly more hybrids, including the x arendsii ones. We can actually dispose of the discussion here with one short statement: the x arendsii hybrids in general cause few if any problems in cultivation in Tromsø. Growing S. cespitosa one has to take care that there is limestone in the soil. Growing S. rosacea and the x arendsii hybrids and similar, one must take care that the soil will not dry out too much, and even in Tromsø full sun may not be the best situation for these plants, half shade being a better choice.
Section Ligulatae next. As mentioned above, two of the ten species in this section are native to North Norway and, not surprisingly, cause no problems in cultivation provided the basic requirements for soil and growth habitat are met. More surprising is the fact that just about any species or hybrid in this section seems to do equally well. I say "surprising" mostly because of the winter conditions that sometimes prevail. Nothing ever seems to bother these plants, sometimes covered in snow and ice for almost 8 months at a time. Come spring they rise out of winter and adverse conditions in prime condition. It is actually a small miracle.
Now for the Porphyrion saxifrages. With more than 100 species listed in this section, and countless hybrids added to that, it is clear that we still have very limited experience in Tromsø even counting Ole P. Olsen's extensive trials. If something very general should be said initially as to hardiness and amenability to cultivation, it appears to us that there is a gradient in the ease with which species, cultivars and hybrids can be grown. This suggested gradient would imply that European species generally are the easier here, with more of the species from the Caucasus and Central Asian region being difficult to grow, and the largest percentage of difficult or impossible species occurring among the Sino-Himalayan plants. It must be emphasized, though, that more extensive trials could modify this tentative conclusion.
Examples of "easy" and "difficult" Saxifrages in Tromsø
Only a fraction of the species and hybrids available have been tried. Thus no extensive listing of easy versus difficult cultivars can be made. Instead I list here some examples of plants which are easily grown, and plants which seem difficult. This then can serve as a general indication to what we can grow and what we can not grow in the open garden in Tromsø.
Examples of some easy species, mentioned at random: S. andersonii, S. aretioides, S. burseriana (most clones, but not all), S. marginata, S. sancta, S. federici-augusti, S. ferdinandi-coburgi, S. juniperifolia, as well as S. iranica, S. caucasica, S. porophylla, and S. sempervivum. And some hybrids which have done well: S. x anglica (many cultivars are good, but not all; an example of difficult S. lilacina giving rise to hybrids which may be easy to grow), S. x apiculata, S. x edithae, S. x elisabethae, S. x irvingii (another lilacina hybrid which is growable) and S. 'Peach Blossom'.
Examples of difficult plants: S. lilacina, S. georgei, S. kotschyii. We actually expect the list of difficult species, and hybrids, to become quite a bit longer, but we just have not had a chance to try that many yet.
As to species from other sections I will only mention a few that are reasonably garden worthy and presently cultivated in Tromsø. From section Ciliatae: S. hirculus, S. flagellaris, S. flagellaris ssp. stenophylla, S. hirculoides and S. parnassifolia. From section Trachyphyllum: S. aspera, S. bronchialis, S. bryoides and S. tricuspidata. Finally, from section Micranthes, S. purpurascens. This latter plant, so far cultivated only by Ole Olsen here, may deserve some additional remarks. Deriving from the Kliuchevskaia Volcano (1100 m) in the Kamchatka peninsula, where it grows in volcanic ash and cold ravines, Ole has grown his plants from seed collected by Jurasek. They are beautiful, distinct plants with dark red flowers and bronze leaves, showing autumn colours. With Ole they grow and flower well, and from year 2000 on will also be seen in the Botanic garden. (For this information I am indebted to Ole P. Olsen).
The Arctic-Alpine Botanic Garden of Tromsø
The Arctic-Alpine Botanic Garden at the University of Tromsø is only 5 years old. Being the world's northernmost botanic garden, one of its major objectives is to show arctic, antarctic, and alpine plants from many parts of the world. The collections are not built on the principles of botanical systematics, but rather on a number of geographical, thematic or botanical themes. Examples are: Himalayan (geographical), Bulbs and Corms (thematic) and Primula (botanical). In the latter category a small Saxifraga collection has been part of the garden since its opening, thanks to the engagement of Ole P. Olsen. At the present time, however, a project to greatly improve and expand this collection is already far advanced. This is largely due to the personal interest and engagement for Tromsø and its Botanic Garden by the Chairman of the Saxifrage Society, Peter Smith. Spurred by his enthusiasm, prominent members of the Saxifrage Society have agreed to help us build a substantial collection. This is of great importance since we are very short of resources, and have a number of unfinished projects and many collections which so far are far from satisfactory. (That said - please remember that 5 years is not very much for a botanic garden anywhere!).
During the summer of 1998, and even more during 1999, extensive restructuring and expansion of the area for the Saxifraga collection has taken place. A large number of cuttings of valuable plants within the three major sections have been donated to the Botanic Garden and are presently being grown on. The first plantings took place in the autumn of 1999. During the summer of 2000 more details and fine structure of the stonework will be installed and planting start. At the present time we expect that about 40 different cultivars in the section Saxifraga, 20 or more different cultivars in section Ligulatae and between 150 - 200 cultivars in the section Porphyrion will make up this collection.
In addition to the plants mentioned above, the area will also display Saxifraga species of the alpine regions of Troms as well as species from the high arctic, including Svalbard and Alaska. In about 2-3 years this Saxifraga collection could become quite outstanding.
Cultivation of a wider selection of Saxifraga in North Norway has a relatively short history. The experience gathered so far in Tromsø suggests that cultivation of this group of alpines in northern Norway could have some real advantages over many other places of more southerly location, due to the climatic conditions. Harsh as they may seem, it is just possible that this is what many true alpines appreciate. Over the next few years it is likely that many more amateurs will be interested in this group of plants. And not least: the Arctic-Alpine Botanic Garden in Tromsø could become the site of one of the more noteworthy collections of Saxifrages grown in the open garden, thanks, among other things, to the positive involvement several members of the Saxifrage Society.