The Rosemoor Exotics

Senior Garden Supervisor John Lanyon takes us on an exotic tour of this lovely Royal Horticultural Society garden, and introduces us to those rarest of rare palms, Juania australis. Photo by Dick Endt of NZ.
John E. Lanyon, Senior Garden Supervisor, Rosemoor Garden
Chamaerops No.29 Winter 1997

Juania australis cultivated at 'Landsendt', New Zealand by Dick Endt, who kindly supplied the Photo

This article examines the palms and other exotic plants cultivated at BHS Garden, Bosemoor, including methods of cultivation, background to Rosemoor, and its climatic conditions.

I was asked to write an article for your publication about the palms and 'exotics' we grow at Rosemoor, so I will concentrate first on the palms, and digress to other plants later.

'Exotics' is an ambiguous word, as many of the plants we cultivate in England are technically exotic and, from my understanding of the main interests of palm enthusiasts such as yourselves, most of these would bore you to tears. I believe the plants you want to hear about are subjects which have a tender streak, together with substance and character, and I will try to satisfy this wish.

First let me introduce Rosemoor. The estate is set in a large river valley near Great Torrington in North Devon. The original eight acre garden was created by Lady Anne Berry, and in 1988 she donated this garden, together with a further 32 acres of sheep-grazed pasture, to the Royal Horticultural Society. On acquiring the estate the Society commissioned a master plan to develop the site, the vision being to create a national display garden to demonstrate as many facets of horticulture as possible, in a similar manner to their garden at Wisley in Surrey. This work commenced in 1989, and the aim was to complete the major construction work within a ten year period.

Initial construction concentrated on providing the correct infrastructure, including the building of a new Visitor's Centre, car park and path network around the estate, with the new garden areas being developed simultaneously. Below the Visitor's Centre the formal theme gardens have been constructed, and these include two rose gardens, a Herb Garden, Foliage Garden, colour theme gardens, Cottage Garden, Winter Garden and, currently under construction, the first of three Model Gardens which are to be on a similar scale to an average domestic garden.

As you move away from the Formal Gardens the plantings become much larger and less formal, and include large areas of shrub plantings, the Stream and Bog Garden, and arboreta areas. It is these new arboretums which then knit into the original garden. Lady Anne S main interest is plants, and her garden is full of interesting and rare subjects. In particular there are interesting collections of rhododendrons, New Zealand plants and dwarf conifers, as well as NCCPG National Collections of both hex and Corn us.

Rosemoor's climatic and growing conditions are very demanding, especially in the newly created areas. Being situated on the north coast of Devon, the garden has an average annual rainfall of 100cm and is subject to cold northerly winds. The valley tends to accentuate all the weather conditions, acting as a frost pocket as well as a funnel for the strong, north and west winds. This can affect garden plants dramatically, and even hardy plants can be killed outright by these stressful conditions. As the garden matures though, the growing conditions are improving as more shelter is created. In a similar manner, the soil at Rosemoor has never been cultivated extensively and therefore it is still a very fragile silty clay loam. To make this into a good garden soil copious quantities of organic matter need to be incorporated.

The plant which triggered this article is Juania australis (Juania or chonta palm), a typical solitary stalked, pinnate leaved, pleonanthic (not dying after flowering) palm which is closely related to Ceroxylon This plant is endemic to the Juan Fernandez Islands and is now restricted to Robinson Crusoe Island, situated just off the coast of Chile on a similar latitude to Santiago. Because of its natural distribution it is very vulnerable, and this is probably also the reason it has never been widely cultivated and is today a rare palm, both in the wild and in cultivation.

Lady Anne has travelled the world extensively, and now lives in New Zealand. On one of her trips she visited a garden in Argentina where Juania was being cultivated and it is from here that she tells us the seed of our plants originated. For this reason we are not sure that it is definitely Juania we are cultivating - it could be a closely related species. The seed was germinated at Rosemoor and had been growing on for a number of years before I joined the staff.

One of my first development projects was to create a tropical border and the Juania, which had by now grown into good specimen plants, at last had a use and were planted out into this area. Each autumn these palms are carefully lifted and containerised before the first major frost occurs. We soon had a dilemma however as each year these palms were growing larger, and glasshouse space more limited. We decided therefore that it was time to try leaving one out over the winter. A shelter was carefully constructed around the best and most established plant, but unfortunately we then experienced the coldest winter for some years, -9 deg.C and frozen for a number of weeks, plus other cold spells. To be honest though, the Juania did not even try, and even mild, early frosts had already caused considerable damage. In addition to this we have given a plant to Tresco Abbey Gardens on the Isles of Scilly, which has not yet had the chance to prove itself, and a pair to Glendurgan, a National Trust Garden in one of the mildest areas of Cornwall. Unfortunately they also had a cold winter (typical!), but I am glad to say the Juania got through and look as though they may grow away if the weather is kind for a couple of years. We are now aiming to keep the remaining plants for a number of years, as they can be bedded out each summer into the tropical border. In the same tropical border Chamaerops humilis (European Fan palm) is planted out permanently, and does best under an evergreen Euonymus fimbriatus, as here it is sun-baked during the summer and during the winter months such evergreens help to shrug off cold weather and keep tender plants sheltered and dry. A Chamaerops in a more open position suffered some frost damage last winter. The last palm used in this area to add to the tropical effect is Trachycarpus fortunei (Chusan palm). This is without doubt the hardiest and easiest palm I have grown. Here we have used it to give the all-important permanent framework to our tropical area and it fulfils this task admirably. The two plants used were moved from another area and the check and stress imposed on them from being moved, together with the sunny conditions, has encouraged these plants to flower earlier than normal. The flower spikes are incredibly large, with golden yellow flower trusses and it is a real joy to be able to see them at such close quarters.

In a neighbouring area known as the Stone Garden, two Trachycarpus wagnerianus have been placed. This area of garden is gradually being planted with very neat, precise plants which look well against the slate stone paving. This palm is without doubt one of the very best recent introductions into general cultivation; it is so near it almost seems to be unreal. Each leaf is a rich fresh green, small and really widespread, curving back with age. The leaves are held quite rigidly, almost spring-loaded, and look like a child's hand reaching out for help. We grew these plants in containers for a number of years in a heavily loam based compost which they seemed to really enjoy. Be warned though, those spring-loaded leaves can snap off easily.

Another palm bedded out each year and used in front of Rosemoor House is Butia capitata (Jelly palm). At the moment this slow growing plant fits into a 45 litre pot, but soon we will have to find it a more permanent position as it is becoming difficult to manage in this way. This season we have grown the climber Rhodochiton atrosanguineum over it and the effect of this fine tender climber running over the grey foliage has been quite outstanding.

A recent development at Rosemoor was the landscaping of a gully around the underpass which joins the two parts of the estate together. Here the plantings are of a woodland nature, focusing on foliage subjects. In particular many ferns and bamboos have been used. Amongst this planting is our last group of palms; Trachycarpus fortunei. Here, in these much cooler conditions, the leaves produced are much more luxuriant and a good dark green. Bamboos also look particularly well in this situation, and are particularly dramatic when raised up on the rocky banks. Many species and forms have been used, the most striking of which at present is Phyllostachys vivax 'Aureocaulis'. This is a vigorous species from eastern China, and this form has golden yellow canes with an occasional green stripe. Another bamboo which gives a good exotic effect is Indocalamus tessellatus. This plant is similar in appearance to the dreaded Sasa, with big paddle-shaped leaves. It grows to 90cm, and produces an evergreen effect which is irreplaceable amongst the giant five-ton boulders we have used in this area. It does run, but luckily is relatively tame in comparison to Sasa.

The rockwork referred to above relates to the Stream and Bog Garden, where luxuriant foliage abounds. In the stream we have planted a rare and very exotic marginal called Thalia dealbata It was carefully placed in one of the warmest pockets where it gets plenty of sun to help it grow away in the spring. Before planting, this plant had been potted very deeply in its container several times so that when planted the crown would be well below the frost level. It is additionally protected by the running water. Thalia is in the Marantaceae family, and the best known plant of this family is the 'Prayer plant', a common house plant. From the United States and Mexico, Thalia dealbata is a typical herbaceous perennial growing to some 3m tall. The paddle-shaped leaves are held on long slender stalks which are terminated by a spike of purple flowers.

In the areas surrounding the Bog Garden at Rosemoor the soil is actually very dry. Here it is impossible to grow most bog plants, so we are always striving to find plants which give dramatic foliage effect but can tolerate these conditions. Aralias are particularly good and we have recently planted Aralia bipinnata, a deciduous, woody plant which grows from a terminal bud in a manner typical of the genus, with leaves to 80cm long. To say this plant is armed is the understatement of the year; there seems to be a good sharp spine in every available space. We have also been experimenting with the herbaceous species of Aralia. These are very interesting foliage plants and at present we have established two species, A. cachemirica and A. continentalis. The former is part of Lady Anne's original collection, and we propagated it both by dividing the original plant and from seed. Herbaceous Aralias grow from a typical clump-forming herbaceous rootstock. This species attains a height of some 2m each year with us. The stem is stout and upright and the typically doubly pinnate foliage is large and bold to 80cm long.. This growth is crowned each year by a 30cm long spike of ghostly white flowers which look just like ivy flowers, followed by purple fruits which set in the autumn. The general appearance and stature in the autumn of these plants always reminds me of the Pokeweed (Phytolacca acinosa).

Another group of plants we have used around the estate is Acacias. A. dealbata has been planted against the wall of Rosemoor House where it benefits from the hot, sunny situation. This plant has now reached the eaves of the house - some 30ft high - and early each spring, when the weather is kind, it is festooned with canary yellow mimosa flowers. Acacia dealbata subalpina is a plant we obtained from an Acacia specialist. This quite obviously is a mountain form of the previous species and is probably the most outstanding individual plant we have. All the growth habits of this plant are condensed to one third of the normal species. It seems to be very hardy as it is free standing in a cold part of the garden and suffers very little frost damage. The last Acacia of note which we have now established is A. pataczekii. This is the same as the famed plant next to the Alpine House at the Royal Botanic Gardens, Kew. A Tasmanian endemic, it is hardy and only produces adult type foliage which is a really metallic blue and looks just like Eucalyptus foliage.

Although Rosemoor has difficult growing conditions, we strive to grow plants which are normally seen in warmer climates. This is achieved by (a) using the different microclimates around the garden, (b) having a good knowledge of which plants are worth experimenting with, and (c) a good understanding of the particular conditions which these plants need to succeed. The best time to see many of these subjects is in the late summer when most are at their luxuriant best.

Postscript. Dick Endt of Auckland, who kindly supplied the photograph, writes about Juania: '...they are growing well at our place. I have another batch of seedlings at present, now 3 years old, which can be shipped to Europe if needed. They are 40 or 5Omm above ground level and the price is US$40 each plus airfreight and handling.' Contact Dick at 'Landsendt', 108 Parker Road, Oratia, Auckland 7, New Zealand. Or fax him on ++64 9 818 6914.


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