Kent Alpine Gardener's Diary
This entry: 04 October 2014 by Tim Ingram
A Day at Kew
I expect all those who visit Botanic Gardens such as Edinburgh and Kew stand partly in awe and partly in envy when viewing the rock garden and alpine plants. Inevitably these are more appreciated individually than en masse and members of the alpine societies must find this botanical representation of the plants especially appealing. At Kew the rock garden is divided into areas planted with species from the different continents (or regions) and amongst those that you will recognise are always unusual and rarely cultivated species that most gardeners would hardly consider for their gardens. If, though, it is this natural diversity that captures your imagination then these more 'oddball' species are often those that are most fascinating. They show how much more there is to know about plants however long you have grown and studied them.
In a Mediterranean climate, where autumn through winter into spring is the growing season, and summer drought enforces dormancy, autumn flowering bulbs are common. They are virtually absent in the British flora so gardeners are likely to only think of planting bulbs - rather than seeing them flower - in the autumn. Once you grow the autumn cyclamen and colchicums of course this all changes, and before long these are joined by crocus and sternbergias and nerines, and occasionally rarer autumn genera.
In the Alpine House at Kew I was especially struck by the autumn Scilla talosi from Crete. The pale nearly white flowers with hints of blue, and black anthers, give this rather beautiful detail. In 'The Flowers of Crete' (Fielding and Turland, 2005) this is described as endemic to rocky places on Dia island (off the northern coast), and close to, but more vigorous (and polyploid) than the widespread pinkish-blue to lilac S. autumnalis. Compare the two in the pictures below.
I have never grown either of these and they are too tender and special for the garden but do make fascinating plants in the alpine house. Add to these the spring flowering S. persica (in our garden) as well as the much more widely grown garden plants S. siberica and S. mischtschenkoana, and you begin to see the true diversity of this genus - and there are so many other species of interest which will grow well in the garden.
More surprising was to see Cyclamen graecum and C. africanum growing and flowering outside on the rock garden, a sign of the relatively mild (and hot) climate at Kew, and in the case of the former the benefit of planting in rocky crevices just as it does in the wild. This is where a rock garden really does score in enabling plants to be grown so naturally.
Here are a few more examples.
The zauschnerias (it's quite hard to think of them more correctly as epilobiums, even though the similarities in their spreading habit, flowers and seed are obvious) give the most vivid colour in the autumn rock garden. In their native California 50 or more selections are grown but fewer flower reliably in the cooler British climate except under glass. When they do they can be spectacular: the plant above is Z. canum ssp. latifolium at Kew, a high altitude form of the species, with rather distinctive rounded leaves compared with the linear foliage of other forms. The picture below shows 'Western Hills' (?) in a Kent garden and illustrates the dramatic but invasive nature of these plants given a dry stony situation. Underplanted with spring bulbs such as tulips, and associated with strong shrubby sages and rosemary and deep rooting Eryngium bourgatii, this habit can be used to advantage.
Just across the path from the zauschneria at Kew is the Californian Wax Currant, Ribes cereum ssp. cereum. This is a species I have not come across before and it makes a beautiful specimen in a rocky crevice.
Both of these genera are nicely discussed by the American horticulturist M. Nevin Smith in 'Native Treasures - Gardening with the Plants of California' (2006), a book dedicated to Wayne Roderick, whose name will be familiar to keen alpine plants-people.
(the plant above this book is the shrubby American sage, Salvia apiana, growing on a raised bed).
It is easy to view plants from the more parochial perspective of British gardens and gardeners (even though there is nowhere in the world where such a diversity of plants is grown) but reading this book gives an impression of the very distinct and fascinating flora of California (especially a chapter on the native oaks, which vary considerably), and the strong interest there is in growing and conserving many of these species. Apart from very familiar plants such as ceanothus and Californian poppies, this flora is little known in cultivation in the UK by comparison with the similar climatic regions of the Mediterranean and South Africa. The ribes are a good start and we have grown R. speciosum for many years, a spectacular if prickly small suckering shrub wreathed in small crimson fuchsia-like flowers early in the year. Several others would be well worth garden room: Golden Currant, R. aureum, and Nevin Smith's personal favourite, the Sierra Gooseberry, R. roezlii.
In the garden these Californian natives can associate contentedly (because they naturally experience similar climates and ecology) with Mediterranean genera such as cistus, phlomis and smaller sub-shrubs. This picture shows Scabiosa minoana, Dianthus fruticosus and Phlomis pitcheri at Kew. few gardens will have rocky shelfs like this, but, at least in the warmer counties, these would grow equally well in gravelly raised beds or 'berms', and suit our dry garden in Kent.
Maybe the extraordinary Spanish Dorycnium fulgurans or Moroccan Arenaria dyris would not engender much interest except from those of botanical bent, but the S. African Kniphofia caulescens is certainly well worth a spot in any garden! This plant of the Drakensberg experiences the opposite to a Mediterranean climate - warm wet summers and dry cold winters - but the adaptability of plants, and adventurousness of gardeners, and most of all the variable British weather, allows all of these to grow together in the same garden as at Kew - with a touch of 'green-fingers'!
In my description of the Autumn AGS Show at Rainham I commented that showing plants like this can be regarded as theatre. The Rock Garden and Alpine House at Kew are even more theatrical, especially where plants are displayed in the latter as they flower (this was just as true in the previous glasshouse and I have many slides of the wonderful mixes of species in previous years). There is a definite skill in growing and showing off plants like this, but it certainly helps to have such a good backdrop!
Here Rhodophiala bifida really draws the eye but it needs the company of other plants to provide contrast. Though hardy in the garden, species of rhodophiala never give a display like this outside (or at least not for us).
Allium callimischon ssp. haemostictum is a little more understated; a curious onion in which the flowering stems look like old dry foliage until it comes into growth in the autumn, but very pretty close-up. In the garden a nice plant for a trough where this detail can be observed closely.
The low warm light of autumn is a particularly lovely time to view the Rock Garden, as leaves begin to turn and late flowering genera such as Persicaria (here P. mollis from the Himalayas) and Salvia (S. uliginosa from S. America) come into their own. The scale of the rock garden is such that these are displayed beautifully.
In some ways a complete contrast to growing rock plants - but in others with great similarities - is this outdoor desert garden nearby. This of course is pure theatre and all the plants will need lifting and protecting over winter, but the idea of creating a naturalistic scene like this is close to sand and rock gardening, and there are many alpine growers who do grow succulents and cacti too. There is a particular appeal in combining plants as they do in Nature in this way, and the third picture shows a simple combination of Aloe and Pelargonium.
A whole day at Kew is still hardly time to take in more than a small part of the garden but not far from the Rock Garden is a planting of drought tolerant perennials and grasses, dominated in the picture below by the especially fine Miscanthus nepalensis. This is less hardy than the large number of selections of M. sinensis, but has done well in a sheltered spot in our garden even through the cold winter of 2011/12. The miscanthus revel in a long hot growing season, which is why so many have been bred in continental Europe, and they must be amongst the most spectacular of grasses, pampas not-with-standing: the third photo shows M. sinensis 'Cosmopolitan' in our front garden now.
Two more plants to finish with - first here is the 'Afghan Hound' (Helianthus salicifolius) of an earlier entry flowering; perhaps not as showy as other sunflowers but eye-catching none-the-less. And second a very nicely trained Abutilon 'Cynthia Pike' on the wall of the Kew Gallery.
The excuse, if one was needed, to go to Kew was to listen to one of the Horticultural Lectures held nearly every week from September to March - in this case Tim Pankhurst of Plantlife talking on 'Why Rare Plants are Rare?' Those people who live nearby are incredibly lucky to be able to listen to speakers such as Mike Nelhams from Tresco, Fergus Garrett and Richard Mabey, amongst others, and including a good number of talks by Kew Diploma Students on their travels around the world. Hopefully we might invite some to speak to our AGS Group down in Kent in the future too...
For my mystery plant in October I have to show one from Kew and this is a plant that I have seen for several years on the rock garden but never anywhere else...
(details of the mystery plants from August and September to come in the next entry... plus a little horticultural excitement courtesy of Great Dixter.)