Kent Alpine Gardener's Diary
This entry: 17 May 2014 by Tim Ingram
The Changing Face of Classification
The Changing Face of Classification
One of the biggest changes in understanding the classification of plants has taken place in relatively recent years with the ability to determine evolutionary relationships much more accurately by the sequencing of DNA. In 1978 the publication of 'Flowering Plants of the World' (edited by V.H.Heywood) described the then known 250 000 species of flowering plants in some 300 families, a really wonderful summary of plants around the world, very accessible to the gardener as well as professional botanist. Now some 40 years later just over 500 plant flowering plant families and over 400 000 species are recognised, and the newest understanding is described in the updated book, 'Flowering Plant Families of the World'. Both of these books are fantastic compendiums of information and the result of a huge amount of careful research and scientific criticism ever since the time of Linnaeus and before (see for example 'The Naming of Names' by Anna Pavord). For anyone who really wants to know about plants they are essential volumes for the shelf, and yet at the same time - because of the immense amount of information and background to botany and taxonomy - hard to assimilate without wide experience of growing and studying plants.
Combine these with 'The Art of Plant Evolution' by W. John Kress and Shirley Sherwood (Kew Publishing, 2009), which succinctly summarises the latest evolutionary understanding of plants using the extraordinary beauty of botanical illustration, and you have a marvellous exposition of the Plant World for anyone who looks at plants beyond their place in the garden alone. Alpine plants constitute perhaps 12 000 or more of these species, across some 2000 genera and 100 families (see the preface to 'Alpine Plants - Ecology for Gardeners' by John Good & David Millward) and so they are of no small interest taxonomically, let alone in many other ways too.
My excuse for describing these books in what is just an alpine growers diary is that it is really impossible to separate the two: growing these plants in the garden is intimately linked to understanding them in scientific ways too. The result is a far richer view of the world and one which must have strong implications in conserving and understanding these plants properly, something which is very much part of the AGS and likely to become more relevant than ever in years to come.
Probably few AGS members will think of plants in quite this way but it does underlie our cultivation and study of alpines and so is worthy of more consideration. In 'The Art of Plant Evolution' well over 10% of the plants pictured can be loosely described as alpines or of interest to alpine gardeners. The picture of Trillium decumbens by Lawrence Greenwood is rather different from traditional botanical painting, with a background of leaves as strong a feature as the plant itself. Some of his paintings were exhibited at the 5th and 6th Rock Garden Conferences in 1981 and 1991. Thirty years ago trilliums were classified in the large and broad Liliaceae, almost all of which of great interest to gardeners. In 'The Plantsman' Vol. 11, p. 89 (1989) Brian Mathew describes the 'Splitting of the Liliaceae' into just over 20 smaller and more uniform family units; the trilliums, along with Paris and Scoliopsis, being included in the Trilliaceae. Now they are often included with genera such as Heloniopsis, Veratrum and Zygadenus in the Melanthiaceae, but certainly from a gardener's point of view the former designation is much easier to accept. Reconciling the ways gardeners and science view plants is never likely to be straightforward, and if your interest is in both there is always likely to be a divide of sorts, which is not to say that the two are not also complementary (thus the very title 'The Art of Plant Evolution'). For the gardener trilliums are simply so distinct and special, and because they are slow to propagate and grow and relatively expensive, require patience and interest to really become features of the garden. They vary from petite species like T. hibbersonii - here in our garden - to the larger and very garden worthy sessile types such as T. chloropetalum - here in Mike and Hazel Brett's garden - and which can often begin to self seed sigificantly when well established.
These plants never fail to attract attention from visitors to the garden, and now that many more are being raised from seed, rather than destructively lifted from the wild, they are becoming much more reliable garden plants.
Fritillarias, which alpine gardeners of all growers must have the greatest knowledge of, are clearly close to lilies themselves and there must be a few instances where actually deciding in which genus to place a plant causes some debate. Other genera in the Liliaceae itself - Erythronium, Nomocharis, Notholirion - are pretty clear cut, at least to the gardener, and Calochortus and Tulipa, although very similar ecologically, are separated in their New and Old World distributions.
Early classification of Paeonia placed it in the Ranunculaceae and close to Glaucidium, but now it is regarded as closer to crassulas and gooseberries in the Order Saxifragales - and within its own monogeneric family Paeoniaceae. Gardeners could certainly be excused for simply admiring the genus on its own terms! These are illustrated in 'The Art of Plant Evolution' by a painting of Paeonia mlokosewitschii by Jeanne Holgate. Almost all species come from Europe and Asia but there are two intriguing members from the western USA, P. brownii and P. californica, of great interest to the plantsperson, even if not to gardeners in general. I can at least show a picture of the former in leaf (a plant that came from Potterton's Nursery) but it has so far not flowered in the sand bed in our garden.
One of the most striking of more recently introduced plants in the genus is P. iranica from the Elburz Mtns in Iran, which Jenny Archibald says 'rendered Jim absolutely speechless when we found it' (JJA 19199 Paeonia sp. nova - see Jenny Archibald, Exclusive Seeds, January 2011 seedlist - online in the Archibald Archive on the Scottish Rock Garden Club website). There is more information about, and pictures of this plant on the Paeonia 2013 thread of the SRGC Forum. Jim and Jenny Archibald held one of the finest collections of species peonies in cultivation, from which they collected and distributed authentic seed. This included another very rarely grown species, P. parnassica, which has the deepest coloured flowers of any that I have seen. The genus also includes P. tenuifolia (and related species) with uniquely finely cut foliage, here shown en masse in a garden in the Czech Republic last May - a truly stunning plant!
One of the most beautiful of all portraits in 'The Art of Plant Evolution' is Gentiana occidentalis by Marjorie Blamey. Gentians of all flowers sum up alpine plants in many eyes and have a world wide distribution (especially rich in the Chinese mountains), and described by the Czech botanist Josef Halda in his finely illustrated monograph 'The Genus Gentiana', as well as in a number of books written for gardeners over past years.
Gentians are classified closely to Amsonia and Asclepias in the family Apocynaceae - compare for example the twining Tweedia caerulea (the hand coloured picture below is taken from the 'Floricultural Cabinet' of the 1830's) - and also the Rubiaceae, all in the distinct Order Gentianales.
As garden plants they can be wonderful in some gardens or shy flowering and difficult in others. In all cases they are worth any effort to please. The autumn flowering species and cultivars, particularly hard for us to grow well in the south-east, are probably the best of all where suited, as shown here at Edrom Nursery on the Scottish borders.
There can be few more brilliant stars than the spring gentian, G. verna, which Joe Elliott famously grew in thousands at his Broadwell Nursery in the Cotswalds, and maintained in dedicated troughs of this plant alone to provide plentiful seed. In Nature this is greatly variable and with a huge range from N. Africa and Europe to the Caucasus, into Asia and as far east as Mongolia; but also in Upper Teesdale in England and the Burren in western Ireland. This picture shows a purple flowered variant in Vladimir Staněk's garden (in which are also grown pure white and palest ice-blue forms).
Gentians do make the loveliest of subjects for botanical illustration, and here is an example by Peggy Dawe at the recent London AGS Show, one amongst a number of fine paintings exhibited.
For gardeners one of the most well known families will be the Scrophulariaceae, which has included genera such as Digitalis, Penstemon and Veronica, as well as others such as the hemi-parasites Pedicularis and Euphrasia. Many of these have now been reassigned to smaller groupings or, in the case of the first three, placed in what was initially the much smaller related family, the Plantaginaceae. The veronicas include very many wonderful small alpine species, as well as being close to the S. Hemisphere hebes (indeed some botanists prefer the family name Veronicaceae), and here are three quite contrasting examples: V. oltensis, V. bombycina (another plant in Vladimir Staněk's garden) and V. pyrolifolia (a young plant in our garden). The latter is particularly fascinating, a Chinese species nicely photographed by Tim Lever in his report for the Merlin Trust (the Yunnan Highlands, Echoes of Home - see www.merlin-trust.org.uk), but why is it given the specific name pyrolifolia rather than pyroliflora?
In contrast to plant families that have been divided into smaller groupings, another familiar one, the Lamiaceae, has grown significantly with inclusion of plants from the Verbenaceae. This family is exquisetely illustrated in 'The Art of Plant Evolution' by dittany, Origanum dictamnus, never an easy plant to overwinter in British gardens, but with many good related species and hybrid cultivars.
These are just a few examples drawn from plants described in one particular book, but of interest to anyone who views plants in the detail expressed in the AGS Bulletin and Journal since its inception. Plants can be grown and compared individually as they are at the Alpine Shows themselves, but also more generally, taxonomically, ecologically and in their geographical distributions. The end result is something more than the sum of the parts.
The yellow Iranian Paeonia described above has now been fully documented by Jānis Rukšāns and Henrik Zetterlund and named Paeonia wendelboi in honour of its original discoverer Professor Per Wendelbo (see the Journal of the Alpine Garden Society Vol. 82, p.230 (2014).