QBARS - v16n1 The Proposed Rhododendron Garden at Strybing Arboretum

The Proposed Rhododendron Garden At Strybing Arboretum
P. H. Brydon, San Francisco, Calif.

R. 'Avalanche' F.C.C.
Fig. 10.  R. 'Avalanche' F.C.C.
Brydon photo

The organization of the American Rhododendron Society, and the subsequent formation of chapters located in the major growing areas throughout the United States has stimulated interest and prompted the membership to support, or initiate, local test gardens devoted to the culture of rhododendrons. At a recent meeting of the California Chapter of the American Rhododendron Society it was proposed that a section of the Strybing Arboretum be allocated for the culture of Rhododendron hybrids and species.
The site which has been chosen is approximately four acres in size, situated near the entrance on South Drive; it includes the north side of Heidelberg Hill, and also that section immediately surrounding the lake and bounded by the Australian and New Zealand sections to the west and south. Because of space limitations it would be impossible to include all the hybrids and species which could conceivably be grown in the Arboretum: therefore it is planned to grow only those which, in the considered judgment of the American Rhododendron Society, are the very best representatives of the genus for this area.
Early in his career as Park Superintendent, John McLaren realized that the climate of San Francisco afforded exceptional advantages for the successful culture of rhododendrons, and it is due to his foresight that, in the minds of gardeners from all over the world. Rhododendrons and Golden Gate Park have become synonymous. We quote from "Local Climatological Data" prepared by the Weather Bureau: "San Francisco-known as the air conditioned city with cool pleasant summers and mild winters. Flowers bloom throughout the year, and warm clothing is needed in every month." This air conditioning is provided by a combination of sea fog and low stratus clouds carried across the northern end of the peninsula from the Pacific Ocean by westerly winds. The steady movement of air from the ocean ensures an equable climate with few - extremes of heat or cold, and the moisture laden breezes help to create the relatively high humidity that is so conducive to the health of rhododendrons, particularly during the months from May to August, when sea fogs are most prevalent and the plants are making their new growth. Records from the Weather Bureau state that "the sun shines on an average of 66% of the daylight hours in downtown San Francisco"; however. in the Golden Gate Park area, this percentage is considerably reduced, due to the fact that there is greater frequency and duration of fogs in the western or coastal side of the city. The average yearly maximum temperature is 62.7° F. with an average minimum of 50.6° F. Quoting again from the Weather Bureau: "During the entire 88 years of temperature records in San Francisco; temperatures have risen to 90° F. or higher on an average of but once a year and dropped below freezing less than once a year. The highest recorded temperature was 97° F. in September 1939 and the lowest was 30° F. in January 1937. The average yearly precipitation since 1905 is 21.75 inches and 84% of this falls between the months of November to March. with the balance spread out through the remaining seven months of the year.
From these records it can be readily understood that we have an extremely unusual climate in the Strybing Arboretum, one that is eminently suited by nature for the growth of rhododendrons. The soil is quite another matter. Here the natural conditions which prevailed prior to the 1870's were anything but ideal, and it is difficult for those who live in San Francisco to visualize the shifting dunes and barren lands which have now become the world-famous Golden Gate Park. The reclamation of the sandy wastes was a task equaled only by the vision of such men as William Hammond Hall, first Superintendent of Parks from 1871 to 1882, and John McLaren, who was Superintendent from 1887 to 1943. They had the inherent love of green. growing things, and the determination to create, and bring to fruition a dream which we now enjoy as a reality. The way was not easy and disappointments were many. Their initial problems were 1) to tie down the constantly moving sand: 2) to provide a growing medium for trees and shrubs: and 3) to select species sufficiently hardy to withstand the ocean winds and thrive in a soil predominantly sand. Barley was sown and harrowed in with the hope that a cover crop might immobilize the shifting dunes. When the annual grass failed to hold against the steady pressure of summer winds they next tried a sowing of the native yellow lupine ( Lupinus arboreus ) but with the exception of a few well protected locations, this proved of no avail. Success was finally achieved by importing seed of beach grass ( Ammophila arenaria ) from Europe, where it had proved effective along the seashores of Denmark, Holland and Great Britain. This robust grass sent down its vigorous roots to firmly anchor the sand, and even when the crowns were buried to a depth of one or more feet by blowing sand, the tough persistent foliage would push its way to the light and continue to thrive. Once the terrain had become stabilized, loam by the trainload was hauled into the park from surrounding areas, and in time it was augmented with animal fertilizer from the street sweepings and corrals of the horse and buggy era. A wide variety of trees and shrubs were planted, including those suggested by European foresters as being the most likely to survive. Yet, of the hundreds that were tried, it remained for our native Monterey cypress ( Cupressus macrocarpa ) and Monterey pine ( Pinus radiata ) to "do what came naturally"; make themselves at home in the rugged conditions which were similar to their native habitat on the Monterey Peninsula. In addition to these two native species, Eucalyptus globulus , the common blue gum and Eucalyptus viminalis , as well as species of Acacia and Leptospermum , proved to be of inestimable value. Today the windbreaks in Golden Gate Park are predominantly of these species.
Coincident with the development of Golden Gate Park, plans for an Arboretum were in the making, and as early as 1870, a plot of 12 acres was set aside for this purpose. However, it was not until 1937 when funds from the Helene Strybing Bequest became available, that construction of the Strybing Arboretum & Botanical Garden was begun, and the late Eric Walther became its first Director. Mr. Walther was extremely fond of rhododendrons and gathered together a fine representation of the better hybrids and quite a few first-class species. According to the records, there were 85 hybrids and 70 species in the Arboretum at one time and they were mostly located in the area designated as China, Japan, and Himalayas. The allocated space was much too small for the number of plants acquired and before many years had elapsed, the plants became hopelessly tangled, and in many cases misshapen from drawing up to the light. About 50% of these can be salvaged, and to them will be added some 65 hybrids and 24 species recently donated to the Arboretum by Mr. Marshall P. Madison, President of the Strybing Arboretum Society. This gift is certainly appreciated, since most of the plants are clonal forms imported directly from the estate of the late Lionel de Rothschild at Exbury, England, and represent many of his finest creations. Seedlings of some 60 species of varying ages are presently in the nursery, and in time will augment the plantings to form the nucleus of the collection.

A shady path in the proposed Rhododendron Garden
Fig. 11.  A shady path in the proposed Rhododendron Garden
Brydon photo

As was explained earlier, the area selected for the Rhododendron Garden is situated around the lake near the entrance on South Drive. No major changes in the existing topography are contemplated: indeed, none are required, for this is one of the most attractive sections of the Arboretum. Over the years under shrubs have crowded together, necessitating their removal. and much has been accomplished by clearing away surplus material, opening up vistas, and relocating paths so that visitors might view the new plantings without obstruction. The soil in the area is comprised of silty loam in varying depths. to which has been added humus materials consisting of decaying leaves, peat moss, and pulverized vegetation from the underbrush. This loose friable material overlies the original sand dunes and, as is to be expected, provides a well drained medium for the culture of rhododendrons. To the south of the lake a grouping of Monterey cypress ( Cupressas macrocarpa ), Douglas fir ( Pseudotsuga menziesii ), and Lawson cypress ( Chamaecyparis lawsoniana ) temper the wind, and in their lee are planted over 50 named varieties of the deciduous Knaphill Azaleas, Exbury Strain. Across the path, and to the west of the azalea planting, is a long, curving border, with an eastern aspect ideally suited for a large group of rhododendrons which have been propagated by Mr. Jack Spring from imported British and Dutch hybrids. The windbreak behind this border includes three magnificent specimens of Torrey pine ( Pines torreyana ) and a nearby handsome tree, over 40 feet high, of Metrosideros tomentosa ), sometimes called the New Zealand Christmas Tree, since in midsummer it is resplendent with terminal clusters of rich crimson flowers. Not far off, and to the foreground, is another New Zealander, Fuchsia excorticata , a tree fuchsia 15 feet high with a distinct trunk some 6 inches in diameter at the base. To the north, a brook meanders along the path side and drops gently to the lake below. Tree ferns ( Cyathea medullaris ) and chain ferns ( Woodwardia radicans ) are well established along the banks, and here and there Gunnera chilensis makes a splendid contrast with its handsome leaves. Overhead. a canopy of redwoods ( Sequoia sempervirens ), alders ( Alnus rubra ) and cluster pines ( Pinus pinaster ) allow a filtered light to penetrate, creating ideal conditions for the large leaved species in the Falconeri and Grande series, and allowing ample head room for years to come. Here also, we hope to plant members of the Arboreum Series.
There are few places in the United States where species and hybrids of the Maddenii Series do better than in Golden Gate Park. This is evidenced by the glorious displays of R. 'Fragrantissimum', R. 'Princess Alice', R. maddenii , R. crassum , R. nuttallii , R. burmanicum , etc. which delight the visitor in the spring. We look forward to the time when we can concentrate all the available species of the Maddenii Series and their near relatives in the Edgeworthii, Boothii, Cinnabarinum and Moupinense series along a broad border, some 400 feet long, which parallels South Drive. There is enough protected area on the north slope of Heidelberg Hill to accommodate quite a few of the Fortunei and Thomsonii series, and in front of them the smaller members of the Neriiflorum Series will be used to skirt the path. In this immediate area there are several magnificent specimens of Magnolia campbellii , one of which is over 35 feet high, and, at the time of this writing, laden with flower buds. Throughout the area, such smaller rhododendron species as are found in the Glaucum and Lapponicum series will be planted along the paths to feather down the larger plants and provide contrasting foliage patterns. The many species in the Triflorum and Heliolepis series will be spotted along the fringes where they will benefit from additional light, so that flowering wood might be initiated and delight us with their mass displays.
From the above account it is obvious that we have a long way to go, and while it may be some years before we can enjoy specimens such as are seen in the older gardens of Great Britain. at least we are investing in the future so that others might have the pleasure of seeing mature plants of these magnificent rhododendrons in full flower. Wm. Hammond Hall and John McLaren began with a dream and acres of shifting sand some 80 years ago. Today we have a tremendous pride in Golden Gate Park, and with a little patience and a touch of perseverance, the Rhododendron Garden in the Strybing Arboretum should become a center of interest for rhododendron enthusiasts from all over the world.