JARS v37n3 - The Grandia Subsection

The Grandia Subsection
Arthur W. Headlam, Bentleigh, Australia

The Grandia subsection, which is generally noted for the stature of the plants and the size of the leaves, with plastered or fine woolly indumentum, is well represented in the National Rhododendron Garden at Olinda, Australia, as well as in many private gardens in the surrounding Dandenong Ranges. Some 25 miles from Melbourne a relatively mild climate prevails making one of the hazards in many other countries, sensitivity to frost, of little consequence. It is more important to ensure that plants are adequately protected from summer sun and hot northerly winds.

Because most of the rhododendrons in this subsection in Australia were originally grown from seed, it is not surprising that there are many variations from one plant to another in color, shape, and the size of the flowers, in foliage, in habit and other characteristics.

Another characteristic, not necessarily confined to those raised in Australia, is the fact that it often takes up to twenty five years or more for plants to flower when raised from seed. It may be of interest that Peter Damman, Convenor of the Species Group and a resident of Olinda, a few years ago moved to a new property, only a mile from his original home, and part of the transfer to the new eleven acre spread involved the lifting and re-planting of his extensive collection of species, many of which were 25 years old. It is interesting that most flowered for the first time the year after the move from his original garden, virtually just on the other side of the road.

Should growers have similar problems, it may well be worth while to try and see if a move, even a short one, would achieve results, but it must be remembered that moving rhododendrons of this age is no small task, the one previously described involved a considerable amount of hard work, even with the aid of mechanical equipment.

A friend who decided to try this method of including a reluctant R. grande to flower, dug a trench around the perimeter of the plant in the spring, with the idea of moving it in the fall, but when the time for the 'operation transplant' arrived, he decided that the job was beyond his ability and filled in the trench. The plant flowered in the following spring, presumably the trenching and consequent root-pruning was sufficient to induce it to flower.

Climatic conditions and sitting generally have a considerable influence upon the size, health and general well being of any rhododendron. In a well sheltered fern gully where the forest floor is continually damp and covered with a thick layer of humus, plants will, given adequate filtered sunlight, invariably do better than a similar plant in a more exposed and drier position. The rich acid volcanic moisture retentive soil of the Dandenongs, combined with an annual rainfall of 50 to 60 inches and mists and fogs during summer months, all help to create ideal conditions. To try and grow any of the large leafed species in Melbourne, only 25 miles distant, is quite another story. Even with careful sitting, adequate watering and mulching, the plants are not to be compared with their counterparts in the Dandenong Ranges. Melbourne's higher temperatures, which usually exceed 100° F., on a number of occasions each year, atmospheric pollution and restriction of a free wind flow by houses and buildings, are probably the main contributing factors.

R. grande , under favorable conditions, may grow into a tree of up to 30 feet, carrying leaves 6 to 12 inches long by 5 inches broad, deep shining above with the main nerves strongly impressed. The new growth is very striking, usually silvery white and sometimes tawny below. The eight lobed flowers are produced in a rounded truss of up to 25, pale rose in bud, opening to white or creamy white with a purple blotch, or pink.

R. sinogrande , with its tree-like habit, may reach a height of 30 feet in cultivation and even more in the wild, carries the largest leaves of the genus, which may be up to 3 feet long by 1 foot broad, shining with nerves impressed above, whilst the lower surface carries a silver-grey or fawn plastered indumentum. It is well represented in the National Rhododendron Garden at Olinda, with forms raised from seed from Brodick and Trewithen, as well as many plants kindly donated by members and nurserymen. The 8 to 10 lobed creamy-white to pale yellow ventricose campanulate flowers, up to 3 inches long with a purple blotch, are carried up to 20 or more to the truss.

It is interesting that R. sinogrande flowered, probably the first for this species in Australia, at Kenron Park, the garden of Mr. and Mrs. Charles Carlsson, in 1966. The parent plant, imported by Bert Chandler & Son's Nursery, from Hillier's of Winchester, England, in 1955, had at this time not flowered. However, Mr. Carlsson's plant, grown from a cutting from the original import, produced seven trusses of clear yellow flowers with a crimson blotch. The northern form, R. sinogrande var. boreale , has flowers of a soft pale yellow with a crimson blotch.

A popular rhododendron in the National Rhododendron Garden at Olinda and in many private gardens in the surrounding Dandenong Ranges is R. mollyanum , named by Dr. Cowan for the Duchess of Montrose. However, under the new classifications this plant takes the name of R. montroseanum . As to its origin, according to the R.H.S. Year Book, 1962, The Rating of Merit of Rhododendron Species by H.R. Fletcher. "This is another of Kingdon Ward's introductions under the numbers 6261 and 6261A, and for a long time masqueraded under the name of R. sinogrande . It seems to be hardly any less hardy than R. macabeanum , and is much more variable". R. montroseanum was photographed on Saturday morning and it was noticed that on each successive day it faded slightly, and by the following Saturday had faded to a pale blush pink. Nevertheless, it was still an attractive flower.

R. giganteum , as the name implies, is generally looked upon as the giant of the genus, and may reach up to 80 feet in the province of Yunnan where it was collected at 9 to 11,000 feet. The leaves are up to 16 inches long by 8 inches broad, elliptic or oblong-elliptic, are dark mat green and glabrous above, with a thin grey or fawn indumentum below. This species, under the new classifications, becomes R. protistum var. giganteum , and carries flowers in a compact truss of up to 25 or more, long tubular campanulate, deep rose-crimson with a slightly deeper crimson blotch.

An interesting event in Australia was the flowering of this species in 1971, after a wait of 44 years: This rhododendron was imported from England (Gill's), in 1927 by Bert Chandler and Son's Como Nursery at The Basin in the foothills of the Dandenong Ranges, and was originally planted on a slope in the nursery, but it did not thrive in this position and was subsequently moved by the late Bert Chandler to a site by a stream in a deep fern gully which, overshadowed by eucalypts and other native trees, permitted filtered sunshine to penetrate and provided a good protection against strong winds, particularly the hot winds of summer.

In 1971, six flower buds were formed and they were anxiously watched as the season progressed. Although some frosts do occur at The Basin, they are few and certainly not as severe as those in the U.K. and parts of the U.S.A., and in due course the trusses carrying up to 25 flowers opened, deep rose-crimson in color, and were greatly admired by many visitors who called to see and photograph them. Unfortunately, Bert Chandler, who died at the age of 90 years, did not see the flowers which he, for so many years looked forward to with great anticipation. It is interesting that the leaves had only some time prior to the flowering, developed a thin grey indumentum. It has been reported that R. protistum var. giganteum suffered severe leaf burn during the hot and dry summer of 1981/2, but following good winter rains, it appears to be recovering. It would be most unfortunate to lose such a fine specimen which is now 54 years old. However, as an insurance against such a contingency, some years ago John Chandler grafted a scion from this plant, which is doing particularly well and should reach the flowering stage in the not too distant future.

Extensive inquiries have revealed that the only other R. protistum var. giganteum to flower is a plant grown by Arnold Teese, a nurseryman and past president of the Society. A number of scions were imported from England in 1964, and one was grafted to a vigorous understock. It is now 6 feet high with a similar spread and has flowered for the past three successive seasons, providing an excellent example of how the flowering time may be shortened by grafting to a suitable understock. The leaves which carry a narrow marginal band of tawny indumentum, also suffered some damage during the hot and dry 1981/2 summer, but this plant also appears to be making a steady recovery.

There are a group of three plants in the species area, labeled R. protistum (ex Trewithen), but being raised from seed, it may well be some considerable time before flowers are produced and it can be definitely established if they are, in fact, R. protistum var. protistum .

There are 7 plants of R. sidereum , a large tree or shrub of up to 20 to 30 feet, with leaves 10 inches long by 2 inches broad, oblong-elliptic to oblong-oblanceolate, dark mat green above, silver grey to fawn below. Flowers are up to 2 inches long, 8 lobed, campanulate, creamy white to clear yellow with a crimson blotch. This species is rather late flowering and was collected N.E. Upper Burma, Yunnan, 9 to 10,000 feet.

R. magnificum , a tree of 60 feet in its native habitat, which may reach 30 to 45 feet in cultivation, carries leaves 18 inches long by 8 inches broad, oblong to oblong-ovate, mat green above and covered below with thin white or greyish-brown indumentum. Flowers are produced in trusses of up to 20, about 2 inches long, tubular-campanulate, rosy-purple, allied to R. protistum and R. giganteum .

R. macabeanum , which grows to a large tree, is well represented in the garden at Olinda, not only in the species section, but in other parts of the garden, making a spectacular display in the spring with their large trusses of up to 25 or more deep yellow flowers. The new foliage in the spring is particularly attractive with its silvery new growth. The leaves, up to 12 inches long, are dark green above with a greyish-white tomentum below.

A truss from one of the 14 plants in the new area was exhibited in the non-competitive section of the Australian Rhododendron Society's early Show in October 1977, and created considerable interest. R. macabeanum is very popular in the Dandenongs, in private gardens as well as the National Garden, because of its attractive flowers, its hardiness and generally very stable habit of consistently producing an attractive display of deep yellow flowers.

This brings to an end the description of some of the Grandia subsection in the National Rhododendron Garden at Olinda, the development of which originally commenced in 1961. Progress has steadily continued and in 1975, the Australian Rhododendron Society began the development of the second and final 50 acres.

A great deal of preparatory work has been necessary, clearing the scrub and undergrowth, removing rocks, grading the surface and forming roads and access tracks, and, finally, a very necessary requirement of providing an adequate water supply. Further financial assistance was received from the Government, without which, the considerable undertaking would have been far beyond the limited resources of the Society.

The development of the final 50 acres of land has given the Society the opportunity of achieving its ultimate goal, the formation of a permanent species garden in an area where growing conditions can only be described as ideal. With sufficient timber protection, particularly for the large leafed members of the genus, and with well drained, acid moisture retentive soil, combined with a climate in which the growing of the most tender species such as plants of the Maddenia subsection present no problems.

Many of the large leafed species were lifted with a ball of soil as large as could be handled, the largest probably being R. sinogrande var. boreale , nine feet high, which must have weighed ¾ of one ton. Some 650 species were planted, watered and settled in the new area in time to get the benefit of the spring rains.

As there is often some considerable variation between plants of the same species, wherever possible, they were planted in groups of three, this was done for two reasons, firstly in the event of a death, all would not be lost, and secondly, if there were any great variation, the poorer form could be disposed of and replaced from plants propagated from the selected forms.

There are, in fact, in most instances, far more than the three as planned for the species due to the generosity of members and nurserymen in donating plants, and as space presented no problems, all donations were gratefully received. A project of such magnitude will not be achieved in a few years, it is a long term one, but with careful selection and propagation, should create considerable interest for rhododendron enthusiasts for many years to come.