Newspaper article The Journal (Newcastle, England)

Why the Wrong Soil Can Lead to the Rhode to Ruin for Unwary Growers

Newspaper article The Journal (Newcastle, England)

Why the Wrong Soil Can Lead to the Rhode to Ruin for Unwary Growers

Article excerpt

My advice over the years to people who have wanted to grow rhododendrons or azaleas has always been the same: Don't bother unless the soil in your garden is acidic.

That is still the answer for those who garden on clay or sandy soils. But, for many others, that might not be the right reply any longer. There is increasing evidence that several kinds of rhododendron will grow and flower well in neutral soil - halfway between alkalinity and acidity - and that some will thrive in lime-rich ground.

So there is definitely hope for gardeners deprived of those beautiful clusters of flowers in scarlet, mauve, yellow, bronze and many other shades.

Calcium, as lime or chalk in the earth, has been thought to cause poor health in general and chlorosis - yellowing of the leaves - in particular, with few flowers being produced and poor growth.

No doubt that is the case with some varieties. For example, Rhododendron indicum is notorious for reacting badly to small amounts of lime. But increasing the lime content of soil has benefited some shrubs.

Anyone who wishes to grow rhododendrons should first establish the soil's pH with an inexpensive soil test kit. If the reading is 6.5 or lower, it may be worth a try.

The best guide is probably trial and error, but spent mushroom compost, which contains lime as well as an acidic peat-type ingredient, has been beneficial in some instances and is available from commercial sources such as mushroom farms.

Varieties which have responded to transplanting into mushroom compost include Rhododendron keleticum, which is low and spreading with crimson-purple flowers, Rhododendron decorum, with white, scented blooms, and red or pink Rhododendron beanianum.

If acidity is in doubt, rhododendrons should be planted with plenty of low-lime compost around the roots - homemade compost based on leafmould or, to be more certain, a proprietary brand of ericaceous compost, specially formulated to be low in lime.

First, it would be wise to experiment with a few shrubs from the range of evergreens known as iron-clad rhododendrons or hardy hybrids, rather than those which are not so readily available. …

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