Kent Alpine Gardener's Diary
This entry: 20 August 2015 by Tim Ingram
Some highlights of summer
'Summer, as my friend Coleridge waggishly remarks, has set in with its usual severity.'
This rather wonderful use of words applies universally because in our garden in the south east, until recently, the severity was actually high temperatures and lack of rain, what most people look for in summer - which impinges on a nurseryman maintaining plants: in the north the severity has been precisely the opposite, cool and dull weather with a lack of sunshine. As far as the plants are concerned, weather, which is transient and variable, is less important than climate which does have geographical logic. The highlights in our garden in summer then are very different from those in many other gardens, and more to the point these plants are those that have generally succeeded well with us over a good number of years and so are suited to our climate. It may be a simple truism to state but this does have relevance to a Society of gardeners because we are not all the same - our gardens and the plants we grow are the result of situation and inclination as much as tradition and comparison. Even just a few miles from us on the north and east coasts of Kent, members in our AGS Group grow plants outside that we have never succeeded with for any length of time because of the moderating effect of the North Sea (not generally regarded as especially warm but a heat sink in the winter months). There are always surprises though, and hardiness or lack thereof is obviously not simply a consequence of temperature or rainfall and the alpine gardener of all gardeners is probably most aware of this and most likely to experiment and succeed with plants that others give up on.
Scabiosa (Lomelosia) cretica
This species, a gift from Margaret Wilson and Peter Jacob whose garden at Walmer on the east Kent coast is relatively mild, is an interesting example. I hadn't expected this to be very hardy but it has grown well now in our colder garden for four or five years, in a sheltered spot. It turns out that the name is misleading because the type specimen - named by Linneaus - came from further west in the Mediterranean when the Cretan endemic (S. minoana) was also included under that name (see 'Flowers of Crete' by Nicholas Turland and John Fielding). Perhaps the latter would prove to be just as hardy though we have grown it and lost it, and this group of shrubby scabious are very attractive plants.
This fascinating relative of the yuccas has been fully hardy in our garden for many years - not always flowering every year, but when it does extremely striking. It also grows in the much colder winter climate of Denver and it is worth noting this comment from Robert Nold in his hugely informative and valuable book 'High and Dry': 'The distribution of H. parviflora in thw wild, Coahuila and Texas (the Big Bend area, and northeast almost to the Oklahoma border), is worth contemplating for those who believe that habitat always determines hardiness'. There is a rarely grown pale yellow form of the species too and it is small enough - similar to the smaller species of yuccas - to associate well with dryland alpines and subshrubs in the garden.
This rare species of Cardoon endemic to Morocco has never set seed in our garden so though long lived and hardy we have so far not managed to propagate and distribute it: we should move a plant, if we can, to a hotter more exposed spot. It was grown originally from seed supplied by Jim and Jenny Archibald and I can do no better than direct you to this entry on the Scottish Rock Garden Club Forum.
Cynara are surely amongst the most aristocratic of thistles and the much better known C. cardunculus can make an astonishing specimen. This too though has only very rarely set seed for us except in particularly hot summers, so we hope that this year may be one of these. The second picture is a smaller and spinier form of C. cardunculus grown at the Chelsea Physic Garden and obtained from Graham Gough at Marchants Plants. It is still considerably more robust than C. hystrix and, as a species, more widely distributed. These plants again highlight the value of wild collections of seed, and often of individual gardens and specialist nurseries in maintaining horticultural diversity, especially of natural species of plants.
Cynara cardunculus (Chelsea Physic Garden form)
On the whole lilies, which are summer growers, are not so effective in our garden even without the ravages of lily beetle. However, the winter growing and early flowering L. candidum does grow well - a fertile form that was grown from seed from Jim and Jenny Archibald. And also so does the beautiful Greek species L. chalcedonicum. Species lilies, in particular, are often so elegant and appealing - there is a fascinating group devoted to them on Facebook: https://www.facebook.com/groups/388428798013664/?fref=ts - that it would be exciting to discover more species tolerant of our drier garden. This plant grows in semi-shade beneath quite a large specimen of the New Zealand Sophora tetraptera. The picture was taken in 2014, a much wetter year, and this hot dry summer has not been so much to its liking but even so it is a good lily for drier situations. It was interesting to read Jon Evan's recent observations on the Discussion pages too and his picture of L. leichtlinii, which suggests we should be more adventurous in trying a wider range of species. They are truly wonderful plants to have in flower in the summer garden.
Acanthus is a genus of extremes. From N.W.Africa come the extraordinary woody species A. sennii and A. eminens which have recently come into cultivation. Most familiar though are the robust garden plants A. mollis and A. spinosus, very striking but often over-dominant and free seeding, difficult to remove because of their tendency to grow so easily from root cuttings. And then the diminutive A. dioscoridis which is quite a variable plant and associates well with other dryland alpines and bulbs. We have grown two forms of this, one with the typically cut leaves of the genus - var. perringii - and the second, pictured below, with smooth-edged leaves. This does run steadily but is attractive and unusual for its short spikes of pink flowers in summer not much more than 30cm or so high. It combines well with sedums and eryngiums in a bed also devoted to bulbs, emerging and growing after most of the bulbs have flowered and are going dormant.
In this same bed we have recently planted this Mediterranean grass - particularly ethereal and rather beautiful - which grows to 1.5m or so and catches the lightest of breeze, which makes it nearly impossible to photograph. This movement even on what seem the stillest of days gives it immense attraction in the centre of the lawn looking from our dining room. In recent years we have been planting more bulbs into the lawn generally and allow the grass to grow long and flower into summer, so ornamental grasses such as Oryzopsis in the beds around continue this theme and take some of the formality away from the garden, giving it more of a meadow-feel which is a typical plant community at this time of year.
There are so many Labiates of interest for hot and dry situations. Along with species of Sideritis we have been steadily growing more origanums, stachys, thymes etc., an interesting family of plants to explore in more detail. This one needs especially poor sandy/gravelly soil to overwinter successfully; it is planted here in 6 inches of pure sharp sand along with that other demanding alpine Onosma albo-rosea. The flower stems are used for making a herbal tea which I must try sometime!
Lotus (Dorycnium) pentaphyllus
This curious little subshrub, so much like clover, has the same strong attraction to bumblebees - insects described in fascinating detail by the entomologist Dave Goulson in his recent book 'A Sting in the Tale'. We first saw this at Michael Wickenden's nursery, Cally Gardens, Gatehouse-of-Fleet, in the SW of Scotland. Unlike the more robust and ever(silver)green Lotus hirsutus which is a widely grown and valuable small shrub for hot situations, L. pentaphyllus dies back to the ground in winter and must be very little seen in gardens. Like the Labiates its attraction to bees makes it a worthwhile addition to the garden - good to watch in high summer.
Centaurea cineraria (gymnocarpa)
Centaurea is a large genus with many potentially good species for warm dry gardens. This species, from Italy, is a particularly fine foliage plant for the hottest of spots. The form we have may be 'Colchester White' which was selected at Ramparts Nursery in the 1960's or 70's by Mrs Desmond Underwood who specialised in growing silver and grey foliage plants. It has never flowered for us, though ordinary forms can have plentiful small mauve flowers. Few plants, other than the rather tender Artemisia arborescens, have foliage as white-silver as this and it combines well with maquis-like plantings of cistus, salvias and other Mediterranean plants.
Eryngium giganteum 'Silver Ghost'
This form of the very familiar biennial eryngium was introduced by Martyn Rix, Jimmy Smart and Dick and Ros Banks from near Trabzon in Turkey in 1982. It differs from 'Miss Willmott's Ghost' in having longer, more spiny and deeply cut floral bracts, if anything even more silvery and ghost-like in the evening garden. Growing here with lavender.