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Graham Rice on Trials

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

AGM update – and sempervivums

Posted by 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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