PRUNING. 335 



indeed all hair-like roots, are as readily destroyed by over-dryness as by 

 moisture, and hence the continual risk of danger to this description of plants 

 when grown in pots. To guard against the extremes of dryness and mois- 

 ture, the pots when small are sometimes plunged in sand or moss, or placed 

 in double pots ; or when the plants are large, shifted into wooden boxes (423), 

 which not being great conductors both of heat and moisture, are more 

 congenial to the roots of all plants. To guard against excess of moisture on 

 the one hand, and the want of it on the other, two very ingenious and use- 

 ful practices have been introduced into the culture of heaths and heath-like 

 plants in pots, by Mr. M'Nab. The first is, always to keep the collar of 

 the stem of the plant a few lines above the general surface of the pots, in 

 consequence of which it is always dry, and not liable to be chilled by evapo- 

 ration, or rotted off by the stagnation of moisture ; and the second consists 

 in mixing with the soil fragments of any coarse, porous stone, from one inch 

 to four or five inches in diameter, such as freestone, which retaining more 

 moisture than the soil, gives it out to the latter when it becomes too dry; 

 arid thus a temporary neglect of watering is not attended with the sudden 

 destruction of the plant, which without these reservoirs of moisture it often 

 is. To counteract the effects of evaporation from the sides of pots, and of 

 sudden changes of atmospheric temperature, the French gardeners very 

 generally employ wooden boxes, even for small plants. Glazed pots have 

 also been proposed to be employed in this country, as in China, by Mr. 

 Forsyth (Gard. Chron., 1841, p. 499); but they have not yet been suffi- 

 ciently tried to admit of our generally recommending them. Mr. Knight 

 is of opinion that, though some plants are injured by having the sides of 

 their pots fully exposed to the air, yet that the taste and flavour of the 

 peach and nectarine, and still more of the strawberry, are greatly improved 

 by it, as well as the period of the maturity of their fruit accelerated. (Hort. 

 Trans, vii., p. 258.) 



750. Growing hardy plants in pots, and especially the more rare kinds 

 of trees and shrubs, for the purpose of transport, and to insure success when 

 they are finally planted out, is one of the most useful purposes to which the 

 potting of plants can be applied. We have already (722) recommended all 

 the more valuable evergreens, and especially those of the pine and fir tribe, 

 only to be purchased in pots ; and the same observations will apply to such 

 deciduous trees and shrubs as make few fibrous roots, such as the Magnolia, 

 and to most rare and valuable herbaceous plants. The care requisite to be 

 taken in transplanting into the open ground plants which have been some 

 years in pots, has also been enlarged on (734). Either the fibrous roots of 

 plants which have for some time been grown in pots should be stretched out 

 at full length, or, if they are too brittle for that purpose, a portion of them 

 should be left as they are to absorb nourishment, and a portion shortened or 

 pruned, in order to produce new fibres to become roots, branching out in 

 every direction. When this is neglected, more especially with trees or 

 shrubs which produce chiefly surface-roots, such as the pine and fir tribe, 

 or which produce few roots, such as the Magnolm, they will often, after 

 being transplanted into the free soil, remain in a stunted state for many 

 years. 



III. Pruning. 



751. Pruning consists in depriving a plant of a portion of its branches, 

 buds, leaves, bark, or roots, in order to produce particular effects on the 



z 2 



