It contains more than 70,000 plants available to buy from UK nurseries and is the most comprehensive directory on the market.
RHS chief horticultural data development manager Janet Cubey said: "When first launched, RHS Plant Finder contained only 22,000 entries, in part a reflection of the narrower range of plants that were available then to the gardener. Since then, the number of entries in genera such as Corydalis, Digitalis, Hamamelis, Lavandula, Pulmonaria and Salvia - to name but a few - has grown hugely and this year's book is no exception, with 400 daylilies and 200 irises being listed for the first time."
According to Cubey, this year's top ten new entries indicate an interest in diversity of colour and texture in foliage as well as in flowers, including four new Heuchera cultivars, two new Clematis, and two new Brunnera.
2010 Top Ten List
Heuchera 'Berry Smoothie'
Heuchera 'Fire Chief'
Heuchera 'Midnight Bayou'
Clematis Reflections ('Evipo035')
Clematis Shimmer ('Evipo028')
Echinacea 'Hot Summer'
Brunnera macrophylla 'King's Ransom' (v)
Brunnera macrophylla 'Emerald Mist' (v)
Diervilla sessilifolia Cool Splash ('Lpdc Podaras') (v)
Heuchera 'Midas Touch'
For more information and to order a copy visit www.rhs.org.uk/rhsplantfinder