Woody Plant Trials at Wisley

The Woody Plant Committee discusses Indigofera howellii.

Last Friday, 'fresh' off the plane, I went to a meeting of the RHS Woody Plant Committee at Wisley. After the business was over, we went out to inspect the trials of woody plants that are currently in progress.

Trialling plants for their garden-worthiness is a major function of the Royal Horticultural Society's work, conducted over all classes of plant. As wide an assemblage of material as possible is procured for each trial, and this is then grown together, with every entry receiving identical treatment. The trial is judged at intervals by the appropriate group from the Trials Committee - sometimes visiting every week or fortnight during the flowering season - and each entry is assessed for its qualities by a panel of experienced horticulturists. The aim is to see which plants perform best and can be granted the Award of Garden Merit for their all round performance: an AGM is an accolade to the plant and a commendation to gardeners. It has nothing to do with novelty, just steady garden performance, so can be won by any cultivar that achieves the standard required.

Clematis 'Purpurea Plena Elegans' dates from Elizabethan times: its extant AGM is likely to be renewed.

The Woody Plant Committee delegates the work of assessing trials to a few of its members who also sit on the Trials Committee, but is responsible for ratifying any awards made, so this was an opportunity for us to have a look at the plants and get an idea of their merits for ourselves. We started with the Clematis viticella trial, grown on the Portsmouth Field. Two plants of each cultivar are grown up a secure wire frame - there are about forty cultivars in the trial. Although many had passed their peak the diversity of flower size, shape and colourin this rather diverse group could be appreciated - but also their vigour, foliage character and resistance to disease, which are all equally important in an assessment. With Raymond Evison, the well-known Clematis breeder and nurseryman from Guernsey, as our Chairman, we were able to be particularly well informed about the background of the cultivars, while our trials members brought us up to date on the relative standings of each cultivar to date, two years into a three year trial. Many of the cultivars are very familiar, but it was good to see some new ones too. I particularly liked 'Evipo036', sold as Confetti, with richly pink nodding flowers (right), a view which was widely shared.

After lunch we went to the other end of the garden to see the trials of Weigela, Indigofera and related legumes, and Buddleja. I skipped the weigelas and only skimmed through the buddlejas as I needed to get home before the effects of an overnight flight took hold.

Buddleja davidii is a species I have reservations about. Spectacular though a bush of, say, 'Pink Delight' or 'Ellen's Blue' is, or the pleasure of seeing a wildling covered in butterflies, I can't easily forgive the problem of the lingering dead brown flowers at the base of the inflorescence, turning the bush dingy before it's really got going, and the invasivity of the species is a major problem. While it has advantages for insects the dominance of the plant causes a diminution in the diversity of everything else. The trial is however a spectacular demonstration of the diversity of B. davidii in gardens, with some other species as well. My favourite, as it was last year, is a short-growing cultivar named 'Camkeep' and sold as Camberwell Beauty (left, above). Although it is a fairly ordinary colour it has the great advantage of having branched inflorescences: this has the benefit of somewhat obscuring the objectionable dead flowers as the side shoots develop and open their buds. The phenomenon is also seen in the more familiar, but much taller cultivar 'Dartmouth' (visible at the right of the image above), and another one I noticed in the trial, 'Antoinette'.

Indigofera is a much less familiar genus, but contains some excellent garden plants - and many that in my opinion are only for collectors. I. heterantha is probably the most widely grown, forming a big bush if unpruned, or coppicing vigorously from the base if cut back in spring, and bearing masses of bright pink flowers all summer. Equally striking, but much less well-known is I. howellii, formerly grown as I. potaninii, which produces its long inflorescences from April to the frost in autumn (see top picture). I have never been terribly impressed by the usually grown stock of I. pendula, which seems a bit 'thin' and underwhelming, and this was very evident in the trial as it was growing next to a greatly superior form, with a more concentrated display of brighter-coloured flowers (right). This has, as yet, no name by which to distinguish it, but its desirability has been demonstrated by the trial and a name will be applied in due course.

A rare Agapanthus

In 1998, or thereabouts, I was sent a packet of seed of Agapanthus walshii, by Barbara Knox-Shaw, of Elgin near Cape Town. It germinated well and seedlings were potted up. Quite a few were given away and I kept some for myself. Most of them died, and since I came to Colesbourne in 2003 I have had a solitary plant, growing slowly in the greenhouse, and never flowering until now. It is potted in a mix of loam and a lot of grit, fed every week in summer with Phostrogen (it's a one-size fits all regime in the Colesbourne greenhouse).

The common Agapanthus in the area around Cape Town is A. africanus - the first of the genus to be discovered and grown in Europe. It is a winter-growing, evergreen plant, and has a reputation for being very tricky to grow: the name, however, is ubiquitous in the horticultural trade, but this material is always one form or another of A. praecox. This is a summer-growing evergreen species that, while somewhat tender, is at least amenable to ordinary pot cultivation and provides many of the best Agapanthus cultivars as selections or hybrids. 

Agapanthus africanus has open-faced flowers held outwards in the umbel, like most members of the genus. It was not surprising then, that when an Agapanthus with pendulous, rather tubular flowers, was discovered at the Cape in 1918, it should be regarded as a new species. It was named A. walshii. Recent studies have shown, however, that africanus and walshii are very closely related, with the result that in their study of the DNA weight of Agapanthus (2003), Graham Duncan and Ben Zonneveld treat this plant as A. africanus subsp. walshii. It is a rare plant in the wild as well as in cultivation, and the largest known site (which Barbara and Graham took me to see in 2004) is being encroached on by what is known in South Africa as 'informal housing' - a shanty-town anywhere else.

The forms of A. africanus are all winter-growing in the wild, which poses problems in the low-light conditions of northern Europe. I have found however, that my plant of subsp. walshii has remained apparently growing, though always very slowly, through the year. It has produced just one fan of neat, short, green leaves, with no sign of an offset, and the current scape has arisen direct from its centre. This worries me rather, as Graham Duncan, in his excellent account of the plant in Curtis's Botanical Magazine, August 2004,  reports that it is prone to die after it flowers. At Kirstenbosch he gets round this by feeding flowering plants heavily with a fertiliser made from concentrated chicken litter, so I must try to find something similar, at least in effect.

I have been surprised at how tall the inflorescence is - I had been expecting something more in proportion with the fan of leaves - but illustrations of wild plants show that it always greatly exceeds the foliage. Although the leaves show no wax, the scape is strongly waxy. The pendulous flowers are very reminiscent of A. inapertus in their tubular shape and posture; they are said to vary in shade of blue in the wild, and white forms are known.

A nice find in the herbaceous border

Female Slow-worm, Anguis fragilis.

Jim Archibald

Dionysia archibaldii

The sad news that Jim Archibald died yesterday has just reached me. Widely recognised as one of the greatest contemporary plant hunters, for nearly fifty years he was at the forefront of plantsmanship, issuing his first seed list in 1962 and then from 1964-75 running The Plantsmen nursery with Eric Smith. In more recent times he and his wife Jenny were best known for their seedlists full of the choicest plants, often available nowhere else, mostly in the range that is often broadly classified as alpine, though dryland and mediterranean might be more accurate. The descriptions and notes were always meticulous and the JJA catalogues are a mine of information. Only this morning I was looking for some information from them, but didn't have the right issue so thought how useful it would be to have them available online or on CD. Not least of the pleasures of reading an Archibald catalogue were Jim's commentaries on matters, or bodies, horticultural. They did not always endear him to the establishment that was the target of his swipes!

Both a scholar and a grower, Jim Archibald's knowledge of plants was both learned and practical - his article 'Silken, sad uncertain queens' on Oncocyclus Irises, in the AGS Bulletin in 1999, demonstrates this to perfection. Although many of the seeds in their list were wild-collected, many were also grown in several large greenhouses at the Archibalds' home in south Wales under immaculate conditions. The contribution Jim and Jenny have made to horticulture has been assessed by Bobby Ward in his book The Plant Hunter's Garden (2004)  and what is probably the first of many tributes to Jim is available on the Scottish Rock Garden Club's website at http://www.srgc.org.uk/smf/index.php?topic=5879.0 .

The image of Dionysia archibaldii is by Jim Almond, borrowed from his site Alpines for the enthusiast. The plant was discovered by Jim Archibald at high atitudes on Zardeh Kuh peak in Iran in 1966, and although difficult to grow has been maintained in cultivation ever since. It was named in Jim's honour by the Norwegian botanist Per Wendelbo.

Breeds of Gloucestershire sale

Once I had crawled out of bed this morning I went down to the annual Breeds of Gloucestershire livestock auction at Cirencester Livestock Market. The best excuse is that I am still looking for a new Silver Sebright cock (see my post of 7 May 2010) - I was certainly not in the market for anything four-footed - but no excuse is really needed. There was a pen of Silver Sebrights in the poultry sale, but I didn't think they were up to standard, so left them well alone.

Gloucestershire has three unique traditional livestock breeds, the Cotswold sheep, Gloucester cattle and Gloucester Old Spot pigs. Cotswold sheep are large, producing wool with a long staple, and big joints of rather fatty meat. With lean meat being generally preferred and wool at a very low price they are now kept more for ornament than anything else - although the Colesbourne flock does a very good job at 'mowing' the grass in the park. A topknot of wool is always left on the head of a Cotswold sheep to show prospective purchasers its potential quality. The other two breeds are both the source of name-protected food.

Single Gloucester cheese has the status of Protected Designation of Origin (like champagne or Parma ham), and must be produced in Gloucestershire on farms that maintain a herd of Gloucester cattle - a bit of a weasel-worded description if you ask me. It is a naturally-coloured hard cheese (unlike the annato-coloured Double Gloucester,which long since escaped to the realm of mass production) with a light taste and texture. The cattle are typically black or reddish, with a white stripe along the back from the tail: as a breed they almost died out after the war, but are now kept in reasonable numbers once again.

Most famous of the three is perhaps the Gloucester Old Spot pig, a traditional large, fat breed that used to be especially associated with the apple orchards of the Severn valley, where they were turned loose to feed on windfalls: it was said that the spots on the skin were derived from bruises where the apples had hit them. As a source of well-flavoured pork they are much prized - we had some Old Spot sausages at the Colesbourne Inn last night - and Old Spot pork has just been given protection in the category Traditional Speciality Guaranteed, implying that the pork has been raised from pedigree animals in the county using traditional methods. Interest in the pig auction seemed to be particularly keen (right).

Newent Dahlia 41

Views from an African garden

Mt Meru from Moivaro

I got back yesterday from my brief trip to Tanzania, where I was helping my old friend Charles Foley prepare a technical report. We were busy at work each day, so I had no chance to get out into the bush and there are no dramatic tales of any sort to tell.

Charles and his family live just outside the northern Tanzanian town of Arusha, well-known as the 'safari capital' of the country, on one of the numerous parasitic cones that pimple the lower slopes of Mt. Meru. The site has a magnificent view of the southern slope of the mountain to its jagged summit, Africa's fifth highest at 4,566 m (14,980')  (above). The vista is always verdant, comprising a mixture of small plots of cultivation (mostly maize and bananas), planted trees and remnant native forest, up to the montane forest cloaking the mountain's slopes (now fortunately included within Arusha National Park). Below the park boundary the greenery conceals the homesteads of a bustling human population, whose mostly gentle noises can be heard from the house - children playing, the chopping of wood, the crowing of a cock - hundreds of cocks at dawn, and at night the barking of a multitude of dogs. But it is the sound of an African village, with only an occasional engine, or blast of a radio to place it in the modern era.

Arusha is noted for its temperate climate and abundant moisture - hence the verdancy - but at this time of year the weather is not at its best, with much low cloud and distinctly chilly temperatures, not what one would expect from tropical Africa at 3 degrees south of the Equator. The Foleys' home is at about 1400 m, well-exposed to the breeze, but sometimes not very far from the cloudbase; sitting inside on Sunday we gradually added layers of clothing to keep warm. Fortunately the clouds thinned sufficiently on Monday afternoon for the upper part of Kilimanjaro (about 70 km away) to become briefly visible (right), but both mountains were rather coy of their appearances.

The compound, which Charles and Lara share with Eddy Husslage and Mary Strauss, covers several acres, and contains a charming mixture of native and ornamental plants. Most of it is native grassland with some surviving indigenous trees, amongst which Erythina abyssinica and the Sausage Tree (Kigelia africana) are especially noteworthy. Most striking on this visit, however, was the flowering of the grass Melinis repens, whose fluffy pink inflorescences light up in the evening sunshine.

Melinis repens

The grassland contains a rich diversity of herbs, including several species in the large legume genus Crotalaria. They may be low-growing annuals to small trees, but all have inflated pods in which the seeds rattle - Crotalus is the generic name for rattlesnakes. Most members of the genus are yellow-flowered, but a few are blue, including C. polysperma, which was in flower this week.

Mary and Lara have added a lot of additional plants to the grounds however - native, ornamental and culinary. There are productive vegetable patches and fruit trees such as coffee, banana and citrus are joined by real exotica such as Litchi chinensis, currently flowering for the first time. Whether the climate is warm enough for it to produce a crop of lychees remains to be seen; it is certainly not cold enough for apples or pears to fruit, though in Arusha town I saw several peach trees flowering well.

Litchi chinensis

Visiting in the dry season meant that the flowering ornamentals were not at their best, but there was plenty to admire and for the sunbirds to work through in their endless quest for nectar and small insects. The South African Tecoma capensis (Bignoniaceae) is seldom out of flower and always attractive with its orange or salmon-pink flowers, while its relative Podranea ricasoliana (left) has magnificent big pink trumpets with hairy throats.

Being on a slope of a hill built up of very free-draining volcanic ejecta means that the garden does not grow the lusher sorts of tropical foliage plants well - but succulents thrive. Several aloes were in flower, including this attractive yellow-flowered species (below). I shall have to sit down with the Flora of Tropical East Africa to try to get an identification for it.

Twenty years ago, when Charles and I first worked in Tanzania, the country was just beginning to emerge from its most desperate period of poverty and goods of all kinds were scarce and hard to come by: we were advised to buy any toilet paper available, for example. Now, in Arusha at least, there is a burgeoning African middle class in addition to a large expat community and one can get whatever one wants, at a price. One of the products of this increasing affluence is the existence of numerous roadside nurseries, producing a wonderful diversity of all kinds of plants.

Roadside nursery in Arusha, Tanzania

African interlude

The whirligig of time, or perhaps the wind of change, has brought me to Tanzania for a few days. Limited internet access, plus the fact I've forgotten my camera cable so can't download pics makes it difficult to post from here, but I am enjoying the scenery, plants and people.