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Graham Rice on Trials

Updates on trials and awards from the Royal Horticultural Society by Graham Rice

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  • Trials reveal plants to avoid (as well as AGM winners)

    Graham Rice on 31 Jul 2009 at 12:11 PM

    Kniphofia 'Flamenco' - as it was when first introduced. Image: ©Benary Samenzucht GmbHOne of the interesting things about the Wisley trials is that not only do they highlight plants which are deserving of an Award of Garden Merit (AGM) but they also highlight plants which are unusually poor  and so serve as a warning to gardeners not to grow them. The Kniphofia trial, one of the season's most colourful and interesting trials, is a case in point.

    Most kniphofias are intended to be propagated by division so that the plants are guaranteed all to be the same. But the trial also includes four entries of kniphofias raised from seed - and these are just not worth growing. The varieties are ‘Border Ballet', ‘Flamenco', ‘New Hybrids' and ‘Royal Castle Hybrids'. ‘Border Ballet', raised by one of the great British plant breeders, the late Ralph Hurst, and ‘Flamenco', which received an award from the European flower trialling organisation Fleuroselect, used to be excellent - but not any more.

    The trouble is that over the years the quality of the stock has deteriorated so much, now the heights and colours and the flower power of the individual plants are far too unpredictable. There are twelve plants of each variety in the trial and last time I checked many weren't flowering at all. ‘Flamenco' was just one that disappointed - the picture (above, from its raiser) shows how good it once was.

    The lesson: grow named kniphofias propagated by division. This is the last year of the trial so there'll be some award winners to tell you about in the autumn.

    Begonia 'Sensation Red' - withdrawn from the trial with mildew. Image: ©RHS TrialsAnother trial which revealed some plants to steer well clear of was the trial of begonias for pots and baskets - which I have to say is absolutely spectacular and well worth a visit. It's been sprayed against mildew but in spite of that precaution two varieties have already been removed owing to severe mildew infection. So if you're thinking of growing the new ‘Martha White' ("bad mildew, plants looking v poor" say the judges' notes) or the popular ‘Sensation Red' ("very bad mildew ") - beware: last week they were taken away and disposed of.

    With this in mind, the judges decided to cease spraying the begonias and so make it easier to assess which really are susceptible to mildew and which are not. And growing almost a hundred varieties together is a severe test. We'll see how it goes...


  • Clematis trial is impressive

    Graham Rice on 27 Jul 2009 at 03:35 PM

    Clematis trial at the RHS Garden at Wisley. Image: ©GardenPhotos.comGrowing a trial of climbers can be difficult, especially if there are a lot to include, but the staff looking after the trial have come up with good solution for the more than sixty varieties of Clematis viticella and its hybrids.

    Each variety is grown on a tall narrow wire mesh column, guided up to the top about 2m/7ft from the ground, then as the shoots stretch up and beyond they're guided back down again. The result is that the flowers stand out from the supports, from the foliage and the stems making them easy to examine and it's also easy to quickly assess just how much bloom each variety is producing. I have to say that I was sceptical when I first saw it all in place, but it really seems to work.

    The one that stood out for me when I looked was Jenny (‘Cedergren'), for although it was less prolific than some the blue flowers, each with an almost white stripe down the centre of each petal, were lovely.

    So far, and we're only half way through the first year of assessment, the panel of expert assessors has been especially impressed by mix of the familiar and the less widely grown.

    Clematis 'Purpurea Plena Elegans' in the trial at the RHS Garden at Wisley. Image: ©GardenPhotos.comSome old favourites, and existing AGM winners, like ‘Madame Julia Correvon' (wine red) and ‘Purpurea Plena Elegans' (double purple, left) have been well received. The more recent favourite ‘Polish Spirit (purple-blue), another existing AGM winner, was noted as flowering all the way down the plant. Less widely grown varieties that were much admired were ‘Viola' (violet blue), the dainty ‘Odoriba' (white with a pink rim) and ‘Walenburg' (cream, edged magenta-purple) as well as ‘Poldice' (white with a purple rim) which I'd never seen before.

    This is a group of clematis that's ideal for growing through other plants like a climbing rose or shrub rose. They're easily managed, you simply cut them back hard every winter or early spring and pull out all the old growth. Seeing them all growing side-by-side in this trial allows you to choose exactly the variety that's ideal in your own garden.


  • Buddlejas in bloom

    Graham Rice on 20 Jul 2009 at 01:19 PM

    Buddleia trial at the RHS Garden at Wisley. Image: ©GardenPhotos.comThe trial of buddlejas at Wisley is located about as far from most of the other trials as it's possible to be. While almost all the other trials are on the trials field, beyond the double herbaceous border and Battleston Hill, the buddlejas and some other shrubs are through the Pinetum at the opposite end of the garden. But it's well worth the walk.

    I took a look just a few days ago and the colour and the scent and the bee buzzing were overpowering. Some varieties were in full flower, some were just getting going while only a few were still to open their first buds.

    There are over one hundred and twenty buddlejas in the trial and the ones that struck me as especially impressive were: ‘Blue Horizon' and ‘Darenth Valley' (white), both with a very upright habit so neighbouring plants are not smothered; ‘Dart's Papillon Blue' in a lovely cool blue shade; and the vivid hybrid ‘Miss Ruby'.

    It was especially interesting to see the very short varieties. The grey-leaved ‘White Ball' was just knee high and covered with white flowers while Peacock (‘Peakeep') with its large cones of vivid purple flowers was the same height.

    Buddleia Peacock ('Peakeep') and 'Pink Delight' at the RHS Garden at Wisley. Image: ©GardenPhotos.comPeacock (‘Peakeep') is one of the British-bred English Butterfly Series, from East Malling in Kent. These are supposed to be noticeably shorter than other buddlejas but while Peacock (‘Peakeep') was about 60cm/2ft high and one of the best on show, Marbled White (‘Markeep'), friom the same series, was more than twice the height and reached 1.68m/56in.

    The other significant dwarf entry in the trial is Lo and BeholdTM 'Blue Chip', a new multi-species hybrid from the USA, which came second in the visitors' favourites vote last year. The odd thing was that while so many other entries were looking spectacular and most of the rest showing plenty of colour - on Lo and BeholdTM 'Blue Chip' there was not a single flower open and only the very first signs of buds.

    Unfortunately, the two new dwarf buddlejas from Thompson & Morgan are too new to be included in the trial and with this being the trial's last season there's no chance for them to be added.

    But right through the summer this trial will be worth a look. And with coloured foliage weigelas growing alongside, and some lovely specimen trees and summer heathers to appreciate on the way, be sure to take a right turn out of the restaurant and enjoy the stroll.


  • Brilliant begonia

    Graham Rice on 07 Jul 2009 at 11:10 PM

    Been a busy week... I've been covering all the new plants on show at the Hampton Court Palace Flower Show over on my RHS New Plants blog. But today, after three early hours dodging the showers at the Show, I headed off to Wisley to dodge the torrential showers rather less successfully judging some of the flower trials.

    Begonia 'Bonfire'. Image: GardenPhotos.comA dozen judges plus our cheerful and efficient secretary, with umbrellas and raincoats in varying states of efficiency, spent the day looking at kniphofias, begonias for containers, amaranthus, alstroemerias, cortaderias, and Triphylla fuchsias. You can tell from that range of plants that there's some exceptional plantspeople on the committee. And there was one plant that stood out from the hundreds we looked at - and amongst the kniphofias and the cortaderias in particular there were some real stars.

    But one hanging basket of Begonia ‘Bonfire' was absolutely stunning.

    There are two main types amongst these begonias for containers: there are the familiar big and blowsy double flowered types - and in recent years these have been joined by a new range of more elegant varieties derived from B. boliviensis and ‘Bonfire' looks to be the best of these