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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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  • Alpines, clematis and peas on the trials this week

    Graham Rice on 29 May 2009 at 08:57 PM

    Roscoea cautleyoides 'Early Form'. Image: GardenPhotos.comLots to see on the trials field at the RHS Garden at Wisley at the moment. I was judging perennials on Tuesday and took the opportunity to take a look at all the other trials on the Portsmouth Field at Wisley.

    Alongside the bergenias at the bottom of the Portsmouth Field is the trial of Roscoea. Recently moved from a private area near the Alpine House, these are  hardy perennial Asian woodlanders with orchid-like flowers and one very obvious feature was apparent. Some plants were in full flower while others were just emerging.

    In full flower and looking very impressive was R. cautleyoides ‘Early Form', it was the most colourful of all the plants in the trial and was not only making fat clumps but spreading at the root.Roscoea cautleyoides 'Early Form', spreading quickly. Image: GardenPhotos.com

    At the other extreme ‘Beesiana' and R. scillifolia were just emerging. This is actually rather a good thing, it proves that roscoeas can be colourful in late spring with other spring woodland flowers and also in summer when the spring woodlanders have faded.

    At the same end of the field, though a little higher up, the trial of Clematis in the Viticella Group was romping away. These are clematis derived, at lest I part, from the late flowering C. viticella which is pruned hard in spring for a late display. Another trial newly moved from less public area, some of the plants had already romped to the tops of their 2.1m/7ft supports and now shoots wave in the air by 60cm/2ft beyond. These included ‘Royal Velours', ‘Jorma', and ‘Södertälje' which are clearly the ones to choose if need a really vigorous plant.

    A friend had just been remarking that her snap peas produced so few tendrils that they had to be tied in so I took a look at the trial. It's true, some had relatively few tendrils and were not self supporting, the trials staff had used soft twine to stop them falling over. One variety, though, produced far more tendrils than any other the others and that was ‘Sugar Lace'. The interesting thing about this is that you can cook pea tendrils. You can sauté them, or cook them with mushrooms and finely chopped leeks.

    Three pea varieties had already begun to flower, an indication of those which will be the first to crop and these were ‘Sugar Ann', ‘Sugar Bon and ‘Norli'.

    Sempervivums on the roof of the Trials Field shelter. Image: GardenPhotos.comFinally, if you take a look at the shelter in the left hand corner as you come down the steps to the trials field - you'll see the sempervivums from the recent trial settling down well on the roof.

     
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  • After the downpour at Wisley - Iris and Kniphofia

    Graham Rice on 26 May 2009 at 10:28 PM

    RHS Tall Bearded Iris trial. Image: ©GardenPhotos.comArrived at Wisley for today's trials assessment session soon after the thunderous downpour - and just look these irises!

    This is the Tall Bearded Iris trial just an hour or two after the torrential rain early this morning. Every flower was still beaded with rain drops and yet - they look spectacular. As soon you start to walk down the steps towards the Portsmouth Field at Wisley where the trials are planted - they just leap out at you. My advice: get down there and see them, make a note of the ones you especially like and check in the RHS Plant Finder which nurseries list them.

    Now - notice that plant at the back? You can hardly miss it. That's the best early flowering Kniphofia (red hot poker) by a million miles - Kniphofia ‘Atlanta'. Today it was genuinely spectacular and was a real star of the Kniphofia trial.

    Kniphofia 'Atlanta'. Image: ©GardenPhotos.comTurns out another branch of the RHS is looking into the origins of Kniphofia ‘Atlanta' and Dr Christopher Whitehouse is leading the investigation: "We know that Neil Treseder of the famous Treseder's Nursery in Truro found it growing in the garden of the Atlanta Hotel in Tintagel in 1962. However, we believe that it was obtained from a Surrey garden 10 years previously where it probably grew under another name.  Although the Atlanta Hotel has been re-developed and Treseder's closed down many years ago, to resolve this conundrum we're looking to find other plants that may have originated from the Atlanta Hotel in the Tintagel area. We'd like people to send photographs of their May-flowering Kniphofia to rhsherbarium@rhs.org.uk to help us in our quest."

    Got that? Please, send any photographs of your May-flowering Kniphofia to rhsherbarium@rhs.org.uk and please be sure to give the name you have for it and where you obtained it.

    Thank you!
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  • AGM update – and sempervivums

    Graham Rice on 16 May 2009 at 01:13 PM

    Sempervivum calcareum 'Sir William Lawrence'. Image: ©GardenPhotos.comHere we bring you lots of early news of the plants which have been awarded the much prized RHS Award of Garden Merit or done well in the trials. Six months ago a full list of the plants awarded the AGM in the previous year was published, new on the scene is a list of plants which have received an AGM more recently.

    Some have already been covered here, but over the next few weeks I'll be looking at the others as well as checking in on the current trials.

    For three years the trials field at Wisley was home to over three hundred sempervivums - houseleeks. These neat, sun-loving, drought tolerant little plants are enjoying something of a revival, in part because this trial revealed their vast variety, how easy they are to grow and how good they look against a gravel mulch.

    Regular assessments over the three years of the trial narrowed the choice of the best to seventeen (plus one only suited to growing in the Alpine House. You'll find them listed in the May 2009 supplement to the AGM list.

    Sempervivum 'Delta'. Image: ©GardenPhotos.comSome of the AGM winners are old favourites like S. calcareum ‘Sir William Lawrence' which I especially liked for its tight and even clusters of prettily coloured rosettes (see first picture) and the deep red ‘Othello' while lesser known varieties like the olive green and red ‘Delta' (second picture) and ‘Spider's Lair' with small, rounded heavily webbed rosettes were also honoured.

    Grow these sempervivums as specimens in small pots or terracotta troughs, in larger troughs, as green roofs, in raised beds, on rock gardens, at the edges of gravel drives and as slowly spreading ground cover on poor soils. Just give them sun and good drainage.

    See the May 2009 AGM supplement to the AGM list

    RHS Plant Finder nurseries list the sempervivums I've mentioned, click the name for sources:
    Sempervivum calcareum ‘Sir William Lawrence'
    Sempervivum ‘Delta'
    Sempervivum ‘Othello'
    Sempervivum ‘Spider's Lair'

     
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  • Bergenias - flowers and foliage

    Graham Rice on 12 May 2009 at 12:16 PM

    Bergenia 'Pink Dragonfly'. Image ©Terra Nova NurseriesI've mentioned the bergenia trial a few times here, it's been one of the most interesting perennial trials of recent years. And at a recent assessment session plantsman and retired nurseryman Chris Sanders suggested that however good its flowers might be, no bergenia should be given an Award of Garden Merit unless it also excelled as a foliage plant. We don't insist on that for, say, hellebores or delphiniums so what's so special about bergenias?

    The point is that bergenia flowers are often damaged by frost - they certainly were this year - so he felt it was unwise to give awards solely for flowers which in some seasons might not provide much of a display at all. Seems fair to me.

    Bergenia 'Glasnevin'. Image: RHS Trials Office/Alison CundyAnd the reverse is also true. As this last winter revealed, the foliage of most bergenias is very tough and can take a great deal of frost and snow so varieties with good foliage should get awards even if the flowers are less impressive. Frankly, if a bergenia has foliage which is sufficiently attractive right through the winter it wouldn't matter to me if it never flowered at all.

    So ‘Glasnevin', for example, had poor flowers which did not open properly but after the snow in February its foliage was very impressive (see picture). While  ‘Beethoven' and ‘Britten', both raised by the great British plant breeder Eric Smith, along with ‘Pink Dragonfly' (see first picture), were unremarkable in foliage but can be very impressive in flower.

    It will be interesting to how the assessors as a whole feel about this issue - all will be revealed when the awards are finalised

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  • Carnation growing - up to date

    Graham Rice on 06 May 2009 at 10:26 PM

    Spray carnation 'Coquette'. Image ©Sue Drew/RHS Trials OfficeThe Wisley trials not only bring awards to the best plants, they also test new ways of growing them.

    In recent years only dedicated specialists (and mass market cut flower growers) have grown perpetual flowering carnations but a new approach has recently been investigated at Wisley, a way in which more of us can grow these exquisitely coloured and superbly scented plants without keeping them permanently in the greenhouse as is so often considered necessary.

    In fact, they can be grown in containers on the patio and two varieties of spray carnations, which are naturally branching and so ideal for this approach, stood out when grown in this way.

    In February, five plants were potted into 10 litre pots of peat free compost. The plant in the centre was left to grow naturally while the four plants set around the edge were pinched back when they had seven or eight pairs of leaves. This pinching encouraged bushy growth on more compact plants and created a more elegant display which was taller in the centre. Discreet support was put in place towards the end of April, and half the stems on the outer plants were again pinched at the end of May.

    Spray carnation 'Coquette'. Image ©Sue Drew/RHS Trials OfficeDuring all these preliminary stages the plants were kept in the greenhouse, with just enough heat to prevent frost; it would interesting to see how they perform with no heat at all. The judging panel noted that they are able to take low temperatures so it would be worth looking at.

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