JARS v54n1 - 'Rhododendrons Down Under'

'Rhododendrons Down Under'
Rhododendrons in Australia And the October 2000 International Conference, Melbourne
Barry Stagoll
National Secretary, Australian Rhododendron Society Inc.

Australia is a dry continent. Even in many of those parts which enjoy relatively abundant precipitation by Australian standards, extended periods of below-average rainfall and shortages of water for irrigation purposes are by no means uncommon. Hot summers are also typical of most parts. Not the sort of place likely to present good conditions for growing rhododendrons, which typically have their origins in moist environments, with relatively cool climates? Well, yes...and no.

Australia is also a vast continent, and there is considerable diversity in regional climatic environments ranging from moist tropical mountain rain forests and seasonally wet monsoonal regions in the north; through dry grasslands, deserts, drought-tolerant native forest and "bushland"; all the way through to wet, cool temperate rain forests in the south.

In the northern rain forests of Queensland, Australia has two known species of endemic rhododendron, both of Section Vireya . Quite similar to one another on casual observation (and only distinguished as separate species earlier this decade), the small, localised populations of Rhododendron lochiae and R. notiale are more southerly-growing brethren of the many vireya species found in Papua New Guinea and West Irian.

However, the purpose here is to discuss rhododendrons in cultivation in Australia. They have long been popular garden subjects, the first (as far as historical records can attest) having been imported in the 1830s, as part of the general movement to establish European-styles of garden (typically "English" gardens), and the ornamental plants popular in such gardens. As many historians and writers have recounted, for early settlers no doubt this had its first origins in a desire to relieve some of the anxieties of life in an isolated setting, accentuated by the unfamiliar - even forbiddingly different - appearance of the Australian landscape and individual Australian species, by supplanting it around settlements with a more familiar landscape.

However, contemporary evidence makes plain that, at least by the third or fourth decade after the initial white settlement, those who could afford to indulge in the hobby of acquiring desirable ornamental plants from throughout the world, both types long-grown in gardens and newly-discovered types, were prepared to do so for its own sake with all the gusto of like-minded citizens in the northern hemisphere. Numerous Australian gardens, both private and public, had quite extensive collections of rhododendrons by the late nineteenth century, and sufficient interest prevailed amongst Australian collectors and nursery proprietors for a reasonably constant flow of imports of additional examples of the genus through the years since.

Rhododendrons today are grown widely, despite the exigencies of climatic conditions which are often not particularly benign towards them. The most accommodating localities for growing cooler-climate "Asiatic" rhododendrons are those such as found generally in the island State of Tasmania in the south (echoed by certain coastal districts of the southern mainland State of Victoria, across Bass Strait), and the more southerly portions of the series of mountain ranges which run north to south along the eastern seaboard of Australia and then sweep westward into Victoria. Other districts in the south can also be nominated as inherently suitable, particularly those, such as the Adelaide Hills in South Australia, offering the temperature-moderating advantage of higher ground. In aggregate terms, the territory in which conditions are reasonably well-suited to rhododendron-growing is quite extensive, and includes many districts in quite close proximity to major population centres. Occasionally, summer temperatures can range a little high for total comfort - but this has its compensations, as for instance the fact that plants of Subsection Maddenia can perform much more to their potential than in many other parts of the rhododendron-growing world.

But the growing of rhododendrons is not confined to such localities. Rhododendrons which would far prefer to be elsewhere are grown, with a sometimes surprising degree of success, in much less benign "fringe" environments by Australian gardeners prepared to persevere in the cause of having them on hand to enjoy. Within the Australian Rhododendron Society, efforts have been made over recent times - partly by polling members - to accumulate some more rigorous information on the spread of rhododendron growing. Some of the locations reported have challenged what were conventional, established notions about likely success with the genus. Many sites have to contend with high summer temperatures, and conditions can often be made more difficult for plants with shallow root systems, and which tend to wilt readily when transpiring rapidly, by exposure to drying winds.

Some of the credit for successful results in the "fringe" areas can be claimed on behalf of Australian hybridizers. Over the years many hybrids have been originated in Australia, many of which have been developed with the deliberate objective of delivering greater tolerance to higher temperatures than those experienced in the typical habitat of rhododendrons in the northern hemisphere, whether in the wild or in cultivation, and also to emphasize early-season flowering (because late-season blooms tend to be quickly spoiled as the season warms up). Indeed, hybridizing activity has been considerable in the rhododendron field, so much so that the country would rate well up-scale internationally on a per-capita basis.

Of course, vireya rhododendrons are also widely grown. In northerly districts (Queensland for instance, but also lower-altitude districts in New South Wales, beyond the adaptability of cooler-climate rhododendrons), aside from a somewhat limited selection of evergreen azalea types, vireyas reign. Although adopted to an extent by the nursery trade, they are still mostly a plant grown by enthusiasts. But they have a big range from which to choose, with regular addition of new hybrids, both Australian-developed and imported.

In the field of vireyas also, former conventional wisdom about the growing conditions required has been largely dismissed. Once, it was considered that, as a generality, they could not cope successfully in the open in the cooler climates of southern Australia, where they would be best enjoyed as potted plants kept in sheltered conditions rather than planted out in the garden. However, it's now clear that, like many other plant species collected from rain forests in elevated situations in the tropics and from sub-tropical areas, vireyas can be acclimatized to temperate localities. This is provided they do not encounter frosts.

They succeed very well in the ground, or, depending on their individual preferences, as epiphytic subjects, in the south, even being found growing happily in gardens at lower elevations and within reasonable proximity of the moderating influence of the sea in both the north and south of Tasmania (in Hobart, we're talking about a location on about latitude 43-on this measure about equivalent, say, to mid-coast Oregon).

Members of the Australian Rhododendron Society Inc., established around forty years ago, have participated in the establishment of several large gardens open to the public throughout the year which feature rhododendron plantings. In other areas where groups of society members are active, close relations are maintained with public botanic gardens, especially in connection with the areas they devote to plants of the rhododendron genus.

The society's Victorian Branch was responsible for establishing and planting out the National Rhododendron Gardens at Olinda, on Mount Dandenong near Melbourne, Australia's second-largest city. Work on the gardens started in 1960, on a site which was made available for this purpose by the State Government of the day.

The Illawarra and North West Tasmania Branches also established large gardens, open to the public, which are planted primarily with plants of the rhododendron genus. In the case of the Illawarra garden, at Woolongong in New South Wales, vireya plantings dominate. The South Australian Branch provides support for the azalea and rhododendron plantings in the Mt. Lofty Botanic Gardens (managed by the Botanic Gardens & Herbarium), and the Southern Tasmania Branch has a close relationship with the Royal Botanic Gardens of Hobart.

To return to the subject of the National Rhododendron Gardens, Olinda, these gardens of over 40 hectares (100 acres) are now officially the responsibility of Parks Victoria-the government agency which manages State National Parks as well as an extensive network of parks and gardens throughout greater Melbourne. They still benefit greatly from the voluntary contribution of expertise and assistance, including gardening labour, by Rhododendron Society members. They include the most extensive and diverse plantings of rhododendrons (and many other plants including plants from genera with reasonably close affinity to rhododendrons, from the largest magnolias to the smallest heaths) in a single garden anywhere in Australia. In fact, it hosts the official Australian collection of rhododendrons under the aegis of the Ornamental Plant Collections Association Inc . The records indicate nearly 500 species, including major recognised sub-species and/or varieties, are represented, over 60 being from Section Vireya . At least 1350 different rhododendron hybrids are recorded.

A feature is the "Australian hybrids" section. A substantial number of the rhododendron hybrids originated in Australia are represented here. An exercise is under way, with the support of the gardens, to acquire examples of those plants not represented, with the aim of maintaining a much more comprehensive collection in the future.

The gardens also offer a unique landscape, combining select trees and plants exotic to Australia with a large variety of indigenous Australian trees and smaller species, forest fern gullies typical of the locality, and magnificent distant views across the "Blue" Dandenong Ranges.

Particularly impressive are the large stands of Mountain Ash ( Eucalyptus regnans ), the world's tallest flowering plant. Under the shelter of these trees, large numbers of "big-leaf" rhododendrons are thriving, many having produced their first flowering less than fifteen years after being established there. Olinda is one of the relatively few gardens around the world which have an extensive collection of these magnificent members of the rhododendron genus, including many mature specimens planted in the early days. The climate is such that the growth rates achieved have been a good deal faster than those experienced in many of the northern hemisphere gardens where such plants exist. The good blooming years get progressively bigger and better.

The National Rhododendron Gardens are open daily throughout the year and enjoy a high level of public visits, as well as attracting a steady stream of visitors with special interests in recreational gardening and professionals in ornamental horticulture.

Visitors attending the "Rhododendrons Down Under" Australia 2000 Conference, in October 2000, will enjoy the opportunity to view and appreciate the National Rhododendron Gardens, as part of this event. The gardens will be featured, with a complete morning session being devoted to a guided inspection.

One of the many positive aspects of an event such as the conference is its expected spin-off for the gardens, as it will bring to them authorities capable of contributing valuable insights and expertise relevant to its future management, development, and promotion. Of course, it's clear that private enthusiasts, as well as those involved with horticulture in many different ways as professionals, also make good use of such opportunities for extending and reinforcing their networks of contacts to mutual potential future advantage.

The conference excursions will also incorporate opportunities to view a variety of other gardens in the Mount Dandenong area, and to visit Melbourne's famed Royal Botanic Gardens, established in 1846.