Monday, 30 August 2010


In our Christmas crackers last year we all found a packet of sunflower seed saved by my mother from plants she had grown, with the promise of prizes for various categories of sunfloweriness next season. These are some of the progeny from my packet, a nice mixture of warm colours. Note the pollen (and pollinators) - these will set seed, unlike the pollen-free F1 hybrids that are now so common, and which must lead to much frustration among those trying to grow sunflowers for bird food.

Friday, 27 August 2010

Evening light

Malus 'Discovery'

Dahlia 'Arabian Night'

Ligularia 'Britt Marie Crawford'

Sedum x rubrotinctum 'Aurora'

Aeonium, variegated

Calamagrostis x acutiflora 'Overdam'

Wednesday, 25 August 2010

The varied colours of Agapanthus

Agapanthus 'Northern Star'

Agapanthus is one of my favourite genera and makes a really valuable contribution to the garden at this time of year. Over the years I have built up a selection of different species and cultivars with considerable diversity of flower colour, shape and inflorescence character; this gallery gives a sample of some of them. Many have come from Pine Cottage Plants in north Devon, where Dick Fulcher has a wonderful collection and nursery specialising in Agapanthus.  The fabulous blue 'Northern Star' (above) is one of his selections and is hardy in the British climate.

Agapanthus 'Sarah', an evergreen cultivar derived from A. praecox and thus better suited to pot cultivation in the UK. It has extra perianth segments, giving it a distinctive appearance.

People seem to expect Agapanthus to be tender. Some are, some aren't. Evergreen species and cultivars, mostly derived from A. praecox, are usually not hardy (although they often survive a normal British winter in a defoliated state), while those derived from deciduous species, especially from A. campanulatus, are usually completely hardy anywhere in Britain, except perhaps the interior Scottish Highlands. Some of these are the Headbourne Hybrids, raised by Lewis Palmer at Headbourne Worthy in Hampshire: many of the named clones are still worth growing, but the name has been bowdlerized by the medley of seedlings sold under the Headbourne Hybrids name. There are intermediates in hardiness, where long-term survival depends on conditions: A. inapertus is hardy in some southern English gardens, but not at Colesbourne. Its narrow pendulous flowers are very distinctive and its influence can be seen in several hybrids, such as 'Midnight Cascade' (below). A. inapertus 'Graskop' (above right), a wild find in South Africa, was for a long time the most darkly desirable and greatly coveted Agapanthus, but now seems sadly small and bright!

Agapanthus 'Midnight Cascade' - probably not very hardy, but I haven't tried it outside yet.

Agapanthus caulescens is another deciduous species that has been used in breeding and selection and seems to be moderately hardy. It can give some interesting flower colours with a purplish hint: this is particularly obvious in 'Liam's Lilac' (left), a Dick Fulcher selection that has been hardy here for several years.

One of the great myths of gardening, endlessly trotted out, is that Agapanthus need to be crowded in a pot (or even in the ground, which seems strange) before they will flower well. Just try it. Crowding almost always means starvation, and aggies are greedy feeders - flowering performance almost always diminishes rapidly once the plants begin to feel starved. They do flower best when properly established, however, but establishment does not need to mean crowded.

Agapanthus 'Loch Hope', currently flowering extremely prolifically at Colesbourne Park (with Phlox 'Natural Feelings');  it is one of the cultivars selected at the Savill Garden in the 1970s and still a superb hardy garden plant. I bought a plant of it from there in 1983, from which this patch is derived. 'Windsor Grey' (below) is another from this stable.

Agapanthus 'Windsor Grey'

Colour varies in all the species, with whites and pale blues occurring occasionally in natural populations (e.g. the pale A. campanulatus subsp. patens, right), and there are innumerable white cultivars in all groups. The one illustrated below is a hardy deciduous plant and I like the yellow-green tips to the buds, but I don't have a name for it. It came from a Dutch friend's garden.

Green-tipped buds are also visible in 'Enigma' (right), an evergreen derivative of A. praecox that I grow in a pot and keep frost-free and dry in winter (even hardy clones dislike being frozen in wet pots in winter), but it is usually admired for its bicolored blue and white appearance. Another bicolored A. praecox, but with a much taller scape ('Enigma' is quite short), and less intense colours, is 'Selma Bock' (below). It has huge heads (when fully expanded) and is a stunning plant for a tub on a terrace.

Agapanthus 'Selma Bock'

Monday, 23 August 2010

Gladiolus watsonioides

Gladiolus watsonioides with Helichrysum nandense on Mt Kenya, October 2007

One of the plants whose flowering I most look forward to each year is Gladiolus watsonioides. This is an old friend from East Africa whose acquaintance I first made on Kilimanjaro in 1990, but have since met on other mountains. It is found only on the higher mountains of Kenya and Tanzania, growing in the forest and high altitude heathland at altitudes of up to 3900 m, making it the highest-growing wild Gladiolus. When growing above the forest it experiences frost almost every night of the year, as well as the unchanging pattern of equal day and night length through the year (Mt Kenya almost straddles the Equator): it is a pattern well characterized by the great Swedish botanist, the late Olov Hedberg, who described the climate as 'winter every night, summer every day.' In these conditions it grows almost year-round and flowers are always to be found, it seems.

In cultivation it is also of uncertain pattern, so in consequence I grow it in the cool greenhouse where its shoots may emerge at any time. Flowering, however, always seems to take place in late summer.

The plant I became familiar with on Kilimanjaro is a slender plant, with small, pale orange-red flowers, generally growing in openings in the upper forest: pretty but not spectacular (left, above). The species was first named from Kilimanjaro specimens in 1886, so when a larger and far more spectacular Gladiolus was found on Mt Kenya it was not unreasonable to give it a separate name, G. mackinderi, in honour of Sir Halford Mackinder who made the first ascent of the mountain in 1899. In my experience this represents a much more robust plant, typically growing in the high altitude heathland (as in the top picture, and above right), with larger, brighter red flowers, very different in appearance to the rather weedy Kilimanjaro plants. For the first time I have plants from both mountains flowering together in the greenhouse and I'm fascinated to see that the differences I know in the wild are also evident in cultivation (as these were obtained from British nurseries I cannot be accused of collector bias!). In the wild it seems that there is a continuum in flower size between these extremes, justifying the view that they are all forms of one species. For gardeners, however, there is no doubt that it is the Mt Kenya form that is the one worth growing.

Gladiolus watsonioides showing the difference between forms from Mt Kenya (upper plant) and Kilimanjaro.

Sunday, 22 August 2010

A Japanese screen

My friend Tomoko Miyashita has sent me pictures and some comments about the useof  the cucurbit Momordica charantia (Bitter Gourd) in Japan, where it is often used, as she does (above), as a fast-growing sun-screen to shade homes from strong westerly sunshine. This year she has planted two cultivars, the traditional green-fruited form, and a new white version, along with the equally fast-growing plant Cardiospermum grandiflorum.

She writes of the Momordica: 'This is not delicious vegetable at all but I am quite happy with this natural curtain.' Although its bitterness is not to my, or her, taste, it is a surprisingly popular vegetable in Asian cuisine and is usually available from Asian shops in this country.

Seeds of Cardiospermum grandiflorum, Heartseed: the heart-shaped white mark on the seed gives both its English and scientific names, but it is clearly intended for turning into a Micky Mouse face, as Tomoko has done here.  The fruits of Momordica charantia are in the immature stage at which they are eaten. When ripe they turn orange and split to reveal red seeds, at which stage they are very decorative, but it needs a hot summer to perform well.

Saturday, 21 August 2010

An Impatiens Tea Party

Impatiens rothii

On the principle of a Snowdrop lunch, where enthusiasts gather to discuss their plants, yesterday afternoon I held an Impatiens Tea Party, for a few enthusiasts of this undervalued genus.Well, most of it is undervalued: Impatiens walleriana, the ordinary Busy Lizzie, is the world's most popular bedding plant, and as such is highly valuable to the horticultural trade, and apparently valued by those who plant it.

The focus yesterday was, however, on unimproved, wild species of this genus of about 1000 known species. They show extraordinary diversity of flower shape and coloration, as well as plant habit. Most are perennial, some are hardy and most not, with a few annuals. Most are from the tropics and subtropics of Africa and especially Asia, with just six species native to the Americas, and one in Europe.The genus fascinated Sir Joseph Hooker, who studied it intensively in his years of 'retirement', and his study of the African species earned Christopher Grey-Wilson his PhD. His monograph Impatiens of Africa (1980) remains the standard work, but there is no single treatment of the Asian multitudes. Their diversity, and the difficulty of making a decent herbarium specimen that retains some hint of the complexity of flower structure, gives taxonomists a sever challenge, and I am sure that there are many more new species to be discovered. In recent years the genus has had major champions in Britain and the United States: Ray Morgan from Swansea, whose book Impatiens, the vibrant world of busy lizzies, balsams and touch-me-nots came out in 2007, and Derick Pitman of Sacramento, 'Mr Impatiens', who runs a website devoted to the genus, with galleries showing a huge number of different species.

One of the more recent species to be named is Impatiens namchabarwensis, described in 2005. The principal author was Ray Morgan, who told us yesterday how it had been found by a Swiss traveller in the Tsangpo Gorge, and who had sent Ray a few seeds. Of these, six germinated, and from these the whole stock in cultivation is descended. With amazing blue flowers it caused a great deal of excitement - the idea of a blue Busy Lizzie loomed in the minds of the breeders - and it rapidly became widely offered in the horticultural trade, sometimes under the false claim that a dwarfer strain had been selected. I got a plant from Ray in 2004 and it soon became evident that it was a very prolific self-sower, as it still is in a dampish border at Colesbourne Park (right, with Roscoea purpurea and Persicaria runcinata). Discussing this yesterday, others in the group said that while it self-sows freely in their greenhouses, it doesn't do so outdoors for them.

Prolific seeding is one of the demerits of some species in the genus, notably I. glandulifera, but when happy most species will produce self-sown seedlings. Among these is the Ethiopian I. rothii (pic at top), which provides a few seedlings for distribution each year. It has proven hardy here over the past five winters, dying down to large tubers like those of I. tinctoria, to which it is related, and emerging in spring to form a wide bush topped wth salmon-pink flowers.

African species are my particular interest, having become familiar with and fond of them during my work in African forests. Most grow in cooler, montane forests, and do not enjoy summer heat. With cooler damper weather, and shortening days, they are now coming towards their peak, especially I. kilimanjari, I. pseudoviola and their hybrids. One of my favourites is I. hoehnelii, in the form from the Cherangani Hills of north-west Kenya (left), which has quite large pink flowers shaped somewhat like butterflies. None of these is hardy (although seed sometimes winters outdoors to germinate in spring), so cuttings have to be taken each autumn and the plants overwintered in a cool greenhouse. There are several hardy Asian species, of which I. omeiana is the most familiar, and the list is growing as people experiment with them.

The 'Impatient Gardeners' gather cuttings of one of the nicest hardy Chinese species, the white form of I. arguta (Roy Lancaster, John & Lynsey Pink, Derry Watkins, Ray Morgan).

Thursday, 19 August 2010

Sustainable snowdrops

Galanthus 'Hippolyta'

This week we have been busy lifting dormant snowdrop bulbs from the garden and nursery. The bulbs are in perfect condition, plump and full - an ideal state for moving them around. When replanted they will soon push out new roots and quickly establish, growing next year as if they had never been moved.

The clump shown above, of the Greatorex hybrid double 'Hippolyta', is typical. It has been in the ground for several years and the bulbs have multiplied well, so there are several layers of them in the clump. If one tried to divide it in growth, as popular custom sugests, you would rip off most of the roots while trying to disentangle the bulbs, leaving each plant in a disadvantaged state for the growing season and resulting in a smaller bulb than if it had been left undisturbed. Last year's roots are still cleartly visible here, showing how long they persist: while not really active, these are very much alive and fleshy.

A clump like this is extracted from the ground in its entirety: at this time of the year the bulbs just fall away from the clump. Then they are graded, with some flowering-size bulbs being retained for sales while others, plus some offsets are replanted in the original (but widened and deepened hole) at a reasonable spacing. These will quickly develop to form a fine flowering clump again within a year or two. A few other smaller bulbs are taken off for replanting elsewhere. This system makes the offtake of bulbs from Colesbourne very sustainable: the spring display is not affected, and indeed enhanced, while providing a stock of bulbs to appear as potted plants on our sales table next February.

'Hippolyta' in flower - only five months or so to go... (for those who are feeling snowdrop-deprived)

Wednesday, 18 August 2010

Monday, 16 August 2010

Salanova® lettuce

Each spring I am the grateful recipient of a box of seed samples from the Dutch vegetable seed company Rijk Zwaan. This is a major breeder and producer of vegetable seeds, with a strong international presence, but as with so many companies its name seldom appears on the produce we buy.

Among the assortment for the past few years have been packets of Rijk Zwaan's recent development in lettuce, the Salanova ® series. What makes them special, in commercial terms, is that they have been bred to have large numbers of small leaves, that fall apart with one cut across the base, thus making them extremely useful for the packed salad market, or for easy preparation in the kitchen (see the Colesbourne-grown specimen, right). A special gadget has even been developed to allow the cut to be made in just the right place.
As a major commercial entity, the Salanova lettuce has a website of its own, and is the subject of a major promotional campaign - under the unfortunate slogan 'Taste the nova way of living'.

The  easy preparation is indeed convenient - and the lettuces are nicely tasty - but I like them for their ornamentality. We grow them in containers outside the cottage door (top picture, red and green multi-leaf butterhead), enjoying their appearance before thinning them out for a salad, and in the vegetable garden they are also very decorative (above, red and green incised-leaf grown in a shallow crate). I think the green multi-leaf butterhead (below) is my favourite, not only for its culinary qualities, but for the tight, beautifully arranged head of leaves in growth, giving a suggestion of the 'quartered' shape of an old-fashioned rose, which increases as the head matures. Cultivation is as easy as for any other lettuce and I find that if a late sowing is grown in crates in the polytunnel they can be picked late into November.

Saturday, 14 August 2010

Friday, 13 August 2010

Radcot House

Yesterday evening the Oxford & District AGS Group visited the garden of Radcot House, near Faringdon, Oxfordshire, home of Robin and Jeanne Stainer. Approaching from Faringdon one gets a brief but wonderful view of the broad sweep of the upper Thames Valley - a gentle landscape, made up of a patchwork of fields, woods and hedges. Radcot is at the centre of this, at the end of an ancient causeway across the Thames and, as our host explained, the village has had a long history, but 'going downhill from Domesday'. Adjacent to the garden is  the site of a Norman fort once held for Matilda, and Radcot House itself was the focus of a Civil War siege, ended when a Parliamentary shell came through the roof and blew up the beer supply. The main part of the current house dates to 1648, but incorporates earlier elements.

In this setting the Stainers are busy making a beautiful garden of about 2.5 acres, with the stated aim of giving a feeling of space. They inherited some great features, including a long allee of beech hedging and some fine tall but narrow yew hedges, that immediately provide the walls for garden rooms, and some noble old fruit trees provide continuity with the past. Much of the garden is designed to be seen and enjoyed from a sitting position - a diversity of seating is provided throughout - which gives a rather different perspective to normal ambulatory viewing. Seated in a beautiful pavilion (below), for example, one is surrounded by the swirling patterns and colours of the prairie-style planting around.

Elsewhere there are more formal borders, planted for vibrant colours, mostly in the blue, pink, purple spectrum, but with here and there a bright, enlivening flash of yellow or orange, and all leavened by plenty of grasses, but equally there are quiet areas, such as the area around the long formal pond where there is minimal planting. I was taken by the beauty of the lawns of fine grass, which reflect the effort that has gone into the garden as much as the borders do.

The photographs in this post were kindly supplied by Nigel Birch, as I had stupidly left my camera at home.

The garden at Radcot House is open for the National Gardens Scheme on Sunday 22nd August and 19th September and is well worth a visit.

Thursday, 12 August 2010

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.

Wednesday, 11 August 2010

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.