The Native Rhododendrons of Switzerland
Jakob Jenny, Solothurn, Switzerland
Translated from German by J. G. Bacher
The mountains of Switzerland as well as of other European countries have but two species of rhododendron: Rhododendron ferrugineum and R. hirsutum. The first is commonly called the rusty leaved Alpine Rose and the other is known as the hairy Alpine Rose. A third species closely related is the R. Loiseleuria procumbens better known as the creeping azalea, however it is not showy in its flowers.
These rhododendrons are often seen in great colonies and lend a distinctive appearance to the steep slopes on which they are present. (Fig. 9) To the livestock raisers they are considered noxious weeds but the tourist world finds them a charming asset on sightseeing tours. These plants are found growing in the upper regions of Swiss Alps near timberline and above. Along the high passes of the main roads they are found in such profusion that the gathering of flowers for bouquets and souvenirs will not bring on any reduction of plants and baskets of flowers are sent to the low land regions during the blooming season. It is not only the tourists who gather these flowers but in many sections the native population will harvest them for sale to florists. To see the great masses of these shrubs in full bloom is an unforgettable experience as whole mountain sides seem to be sheets of color. The rosy carmine color of the corollas seem to cover hillsides and step slopes with a brilliance never attained in the low lands due to clear atmosphere and ultra violet rays. The flowering period comes according to seasons from late June to July and August. Usually soon after the snow melts the flowers emerge frequently before the ground has even a chance to become green. The lower limit of these rhododendrons is usually near the 4000 to 5000 ft. elevations emerging from the timberline to 7000 ft. or over in some localities. They grow on moist humus, sandy soils and may be found as a ground cover in thin forests. They seem to prefer the north exposures and moraines of early glaciers, yet never on windswept peaks or dry locations. Sunny warm spots are avoided by them due to their sensitivity to frost damage when young. Preferred are shady locations where snow melts tardily and growth is not prematurely encouraged.
It is assumed that in early days rhododendrons were growing throughout Switzerland as there are a few spots in the lower regions where early day survivors may yet be seen sheltered against eradication by laws of conservation. On the Italian side of the Alps a few of these shrubs are found in sanctuaries near Langensee at less than 1000 ft. elevation. The alpine rhododendrons do stand extremely low temperatures in the mountains as their foliage is leathery, tough, and the buds are covered by scaly bracts which serve as a shelter against severest weather. In our gardens the rusty leaved Alpine rose is a great rarity as it will not transplant successfully due to climatic differences perhaps, and the only method is to raise them from seed or cuttings. To be cultivated successfully they must be given the same sort of soil to grow in as they have in their native state. This soil may consist of leaf mould, sandy earth, peat moss and must be lime free. The species sensitiveness to late frosts must be borne in mind for in their native regions they are sheltered by snow until summer time and since they are intolerant to dryness ample moisture must be provided if the plants are expected to do their best. Companion plants of rhododendrons in Switzerland are Junipers, Huckleberries, Vacciniums, dwarf alders Erica and alpine Daphnes. R. ferrugineum is found widely scattered over most of the European regions such as the Jura chain. Here they grow as slender branch plants between 3 to 4 ft. high but are flattened out by the yearly masses of snow in the winter while the foliage remains fully alive towards the tips only. In the spring they grow erect after the snow melts away but always have a gnarled twisted appearance. The upper surface of the leaves is deep green and smooth while the lower side is very scaly, first a light greenish brown, and later with maturity a rusty brown. The form of the leaves is elongated, elliptic, to lance shaped ½ to 2½ inches long and less than an inch wide with the edges rolled slightly over and frequently assuming a funnel shape. The inflorescence is a terminal cluster of flowers of crimson color less than one inch in diameter with the tube of the corolla about the same length. It has been observed that where soils are more than normally acid the color is intensified and for cut flowers one chooses plants with the darker bloom. When the buds are about to open, they are cut and if allowed to flower indoor the color will be much softer than out in the sun. Growth of the plants is very slow and bushes may attain an age of 100 years or more without undue spread, so promiscuous cutting should be avoided. R. hirsutum or hairy Alpine Rose is much more widely distributed than the preceding variety and seems to be tolerant to limestone to a certain extent. Growth seems to be much more compact and it is earlier to flower, but bushes rarely exceed 2 ft. in height. The leaves are more of alight green color, broader than the preceding species and perhaps a bit longer. The flowers are more widely funnel form, a lighter color of crimson hue and while not as profuse in quantity, their larger size is more pleasing. Since the soil requirements are so different from that of R. ferrugineum their companion plants, the two rarely grow together for one often finds R. hirsutum growing on white limestone rock. The light green foliage and brilliant light red color of R. hirsutum growing on a base of white rock produces a stunning picture.
Like most other plants one finds the albino form occasionally, yet rarely are they grown or offered for sale by growers. Collectors of rare forms have also discovered several locations of the Swiss mountains where these white forms have been crossed in nature and brought about a hybrid known as 'Intermedium' a hybrid between the white and red form. In cultivation a report is made of a cross between R. ferrugineum and R. minus in the volume Outdoor Rhododendrons by J. Berg & G. Krussman, Germany. Rhododendron to the Swiss livestock producer is a damnable worthless weed not even of value for fuel, for the branches are too slender, and the natives try to eradicate them. It has been found that pasturing sheep is the most economical method of elimination. It appears that sheep dung is a killing poison to the brush of rhododendrons.
These regions of profuse alpine rhododendrons often shelter the snow grouse, marmots, and the mountain deer. Gall disease occasionally is noted on rhododendron of the Alps.