422 



SCIENCE OF GARDENING. Part II. 



sequently it is very differently circumstanced in the day and in the night, though the tem- 

 perature of the air in the shade at both periods may be very nearly the same. I suspect," 

 he continues, " that a large portion of the blossoms of the cherry and other fruit-trees in 

 the forcing-house often proves abortive, because they are forced by too high and uniform 

 a temperature, to expand before the sap of the tree is properly prepared to nourish them. 

 I have, therefore, been led, during the last three years, to try the effects of keeping up a 

 much higher temperature in the day than in the night. As early in the spring as I 

 wished the blossoms of my peach-trees to unfold, my house was made warm during the 

 middle of the day ; but towards night it was suffered to cool, and the trees were then 

 sprinkled, by means of a large syringe, with clear water, as nearly at the temperature at 

 which that usually rises from the ground, as I could obtain it ; and little or no artificial 

 heat was given during the night, unless there appeared a prospect of frost. Under this 

 mode of treatment, the blossoms advanced with very great vigor, and as rapidly as I 

 wished them, and presented, when expanded, a larger size than I had ever before seen of 

 the same varieties. Another ill effect of high temperature during the night is, that it 

 exhausts the excitability of the tree much more rapidly than it promotes the growth, or ac- 

 celerates the maturity of the fruit ; which is in consequence ill supplied with nutriment, 

 at the period of its ripening, when most nutriment is probably wanted. The muscat of 

 Alexandria and other late grapes are, owing to this cause, often seen to wither upon the 

 branch in a very imperfect state of maturity ; and the want of richness and flavor in 

 other forced fruit is, I am very confident, often attributable to the same cause. There 

 are few peach-houses, or indeed forcing-houses of any kind in this country, in which the 

 temperature does not exceed, during the night, in the months of April and May, very 

 greatly that of the warmest valley in Jamaica in the hottest period of the year : and there 

 are probably as few forcing-houses in which the trees are not more strongly stimulated 

 by the close and damp air of the night, than by the temperature of the dry air of the noon 

 of the following day. The practice which occasions this cannot be right ; it is in direct 

 opposition to nature." (Hort. Trans, vol. ii. p. 130.) 



2199. Air. Knight considers that gardeners often and widely err, " by too freely 

 admitting the external air during the day, particularly in bright weather. Plants gene- 

 rally grow best, and fruits swell most rapidly, in a warm and moist atmosphere ; and 

 change of air is, to a very limited extent, necessary or beneficial. The mature leaves of 

 plants, and according to Saussure, the green fruits (grapes at least), when exposed to the 

 influence of light, take up carbon from the surrounding air, whilst the same substance is 

 given out by every other part of the plant f so that the purity of air, when confined in 

 close vessels, has often been found little changed at the end of two or three days by the 

 growth of plants in it. But even if plants required as pure air, as hot-blooded animals, 

 the buoyancy of the heated air, in every forcing-house, would occasion it to escape and 

 change as rapidly, and indeed much more rapidly, than would be necessary. It may be 

 objected, that plants do not thrive, and that the skins of grapes are thick, and other fruits 

 without flavor in crowded forcing-houses ; but in these it is probably light, rather than a 

 more rapid change of air that is wanting. When fruits approach to maturity such an in- 

 crease of ventilation, as will give the requisite degree of dryness to air within the house, 

 is highly beneficial ; provided it be not increased to such an extent as to reduce the tem- 

 perature of the house much below the degree in which the fruit has previously grown, 

 and thus retard its progress to maturity. The good effect of opening a peach-house, by 

 taking off the lights of its roof, during the period of the last swelling of the fruit, appears 

 to have led many gardeners to over-rate greatly the beneficial influence of a free current 

 of air upon ripening fruits ; for I have never found ventilation to give the proper flavor 

 or colofr to a peach, unless that fruit was at the same time exposed to the sun without the 

 intervention of glass ; and the most excellent peaches 1 have ever been able to raise, were 

 obtained under circumstances where change of air was as much as possible prevented con- 

 sistently with the admission of light (without glass) to a single tree." 



2200. Water. The supplies of water given to plants should be regulated by the sup- 

 plies of heat, the nature of the plant, its state in regard to growth, and the object for which 

 it is cultivated. Abundance of heat should generally be succeeded by copious waterings, 

 unless the nature of the plant, as its succulency, or its dormant state in regard to growth, 

 render that improper. Plants cultivated for their fruits should be less watered during 

 the ripening season than such as are grown for their effect ; a dry atmosphere being most 

 conducive to flavor. The succulent shoots of trees, Knight observes, always appear to 

 grow most rapidly, in a damp heat, during the night ; but it is rather elongation than 

 growth, which then takes place. The spaces between the bases of the leaves become 

 longer, but no new organs are added ; and the tree, under such circumstances, may with 

 much more reason be said to be drawn, than to grow ; for the same quantity only of ma- 

 terial is extended to a greater length, as in the elongation of a wire. 



