Experiments on podzolized heather moor at Allerston Forest have shown that a heather mulch applied around checked Sitka spruce ( Picea sitcbensis Carr.), Norway spruce ( P. abies Karst.), and Lawson cypress ( Cbamaecyparis lawsoniana Parl.), or more simply the elimination of living heather by surface hoeing, produces improved colour and vigour of the trees. It has also been demonstrated that the addition of a nitrogenous fertilizer to checked Sitka spruce can, at least temporarily, alleviate the condition of check.
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J.A. Weatherell (1953) studied this question.