THINNING. 



349 



are, that the sap whicli would have been ehiborated by the leaves cut off, 

 and which would have added to the strength of the tree and its roots, is lost. 

 In the case of trees already sufficiently strong this is no disadvantage, but 

 in the case of those which are too weak it is a positive loss. The summer 

 season is found better than any other for pruning trees which gum, such as 

 the cherry and the plum, provided too much foliage is not thereby taken 

 away ; and it is also considered favourable for resinous trees. The autumn, 

 on the other hand, is considered the best for trees that are apt to suffer from 

 bleeding, such as the vine, the birch, and some species of maple. Evergreens 

 may be pruned just before Midsummer, or in spring, before they have begun 

 to develop their buds. 



§ IV. Thinning. 



780. Thinning is an operation founded on a general knowledge of the laws 

 of vegetation and on the habits and bulk of particular plants. Its object is 

 to allow sufficient space to entire plants, or to the parts of plants, to attain 

 certain required dimensions and particular properties. When plants stand 

 too close together for attaining these purposes, whether from want of nou- 

 rishment at the root, or light and air at the top, they are thinned out ; and 

 when branches, leaves, flowers, and fi'uit are too numerous on an individual 

 plant to be properly nourished, and exposed to the sun and air, they also are 

 thinned out. As this last operation is effected by pruning, it requires no 

 farther notice in this article, which is confined to the thinning out of entire 

 plants by uprooting them. Thinning by uprooting is performed by the 

 hand alone, when the plants are small ; and when they are larger, by the aid 

 of the trowel, spade, pick, or other implements (393, 397, and 400). The 

 subject may be considered with reference to seedling crops in gardens, and 

 transplanted crops in plantations. Transplanted crops in gardens, being 

 generally of short duration, are placed at such distances at first as mostly to 

 render future thinning unnecessary. One general rule in thinning is that 

 the plants to be removed, when they cannot be taken away all round the 

 plant to be left, should be taken from the east and west sides of it, in conse- 

 quence of which it will receive the sun and air on two sides instead of on 

 one, which would be the case if thinning took place only on the south side ; 

 while if it were limited to the north side, air would be admitted, but no sun. 



781. Seedling crops in gardens. — To make sure of a sufficient number of 

 plants, and of their distribution over every part of the surface in broadcast 

 crops (569), or along every part of the row in crops sown in drills, much 

 more seed is sown than is required for the number of plants requisite for a 

 crop. As soon as the plants from these seeds make their appearance, and 

 are considered safe fi-om accidents or insects, all or the greater part of those 

 which are not judged necessary for producing a crop are pulled and thrown 

 away, hoed up and left to die on the spot, or in some cases taken up by the 

 trowel or spade and transplanted elsewhere. The distance at which the 

 remaining plants are left depends on their nature and habit, on the richness 

 or poverty of the soil, and on the kind of crop required. For example, in 

 thinning out an autumnal crop of turnips, the distances between the plants 

 left will be much less than in thinning out a spring crop ; because in the 

 latter case, the plants being destined to benefit by the warmth and light of 

 summer, their roots will attain a much larger size than those of the autumn- 

 sown crop. On the other hand, an autumnal crop of spinach will be thinned 



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