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Soil pH, INKARHO rhododendron, SPAD, calcifuge, chlorosis
Recently a consortium of German plant breeders claims to have developed a lime-tolerant rootstock (INKARHO®). Using isolated beds at RHS Garden Wisley, with soil pH chemically manipulated, four rhododendron cultivars were assessed on INKARHO and Cunninghams’s White (a naturally lime-tolerant rootstock) rootstocks and their own natural root system. A SPAD 502 chlorophyll meter, whose output is a measure of chlorophyll content, was used to assess plant health.
Those who garden on alkaline soils will be able to choose a cultivar of rhododendron that will grow sufficiently well in such conditions without the need for soil amendments.
Advice on understanding soil types
Alexander P D (2008). Are INKARHO rhododendrons more lime tolerant than traditional calcifuge rhododendrons?
SEESOIL, Journal of the South East England Soils Discussion Group, 17, 8-17.
Alexander P D (2002). An investigation into the performance of rhododendrons on lime-tolerant rootstocks. Poster presented to International Rhododendron Conference. Proceedings Rhododendrons in Horticulture and Science, published by RBG Edinburgh, 2003, pp.273 -277.
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.