WATERING. 



383 



822. The specific purposes for which water is used in Horticulture are numer- 

 ous. In general it may be applied wherever a stimulus is wanted to growth, 

 unless indeed the soil be already sufficiently moist. It is given to newly 

 sown seeds, or newly planted plants ; for the purpose of setting blossoms, 

 swelling fruits, increasing the number and succulency of leaves ; conveying 

 manure held in suspension ; conveying matter for destroying insects, or 

 parasitic fungi, such as the mildew ; or poisoning plants on walls or gravel 

 walks ; for causing substances in powder to adhere to plants, as in applying 

 sulphur and other articles ; for clearing the leaves and stems of plants from 

 dust or other foreign matters ; for accelerating vegetation when the water is 

 warmer than the soil ; for retarding it when it is cooler ; for thawing frozen 

 plants ; for forming steam or dew in plant structures ; for rooting cuttings 

 of some kinds of plants (602) ; for growing aquatics, for heating plant struc- 

 tures, and for producing fountains and other aquatic ornaments. Water 

 in the form of snow, forms a valuable protection to low plants when they can 

 be covered by it, acting as a non-conductor of the heat of the soil, and pre- 

 venting it from escaping into the atmosphere ; and water as ice is an object 

 of the gardener's care, the filling of the ice-house being generally committed 

 to him. On the quantity of rain or snow which falls in any country, and on 

 the proportions which fall in different seasons of the year, depends, as we 

 have already seen, (140 to 144,) the natural vegetation of that country, its 

 agriculture, and all that part of its horticulture which is carried on in the 

 open garden. 



823. The ordinary sources from which water is obtained in gardens are 

 chiefly wells, and the collection of rain water in cisterns ; but it occasionally 

 happens that a natural stream passes through or near the garden, or that 

 water is conveyed to it by pipes or drains from some abundant source. In 

 whichever w^ay water is supplied it ought always to be exposed in a pond or 

 basin, so as to be warmed by the sun to the same temperature as the surface 

 of the soil before being used ; unless indeed the object be to retard vegetation 

 by its coldness, which can very seldom be the case. Some very interesting 

 experiments were made by Mr. Gregor Drummond, in 1826, on the com- 

 parative effects of spring water and pond water, in lowering or raising the 

 temperature of the soil of a peach border, which it may be useful to quote. 



1. " The first experiment was made on the 10th of May. At the depth 

 of 18 inches the temperature of the border was 64°, and that of the spring- 

 water used 46°. In twenty-four hours after, the temperature of the border 

 was reduced to 52°, or had lost 12°. At the same time the temperature ot 

 the soil being 64° as above, and heat of the pond water 67°, the soil at the 

 close of twenty-four hours was 66°, or instead of losing 12°, had gained 2°. 



2. "June 20th the second watering was given. The temperature of the 

 border at the depth of 18 inches was now 74°, and that of the spring water 

 52°. In twenty-four hours the border was reduced to 58°, or had lost 16°. 



" At the station where the pond water was used the temperature of the 

 border at the above-mentioned depth was 77°, and that of the water 82°. In 

 twenty-four hours the temperature of the border was 80", or had gained 8°. 



8. "The third and last watering was performed on the 28th of July. 

 The temperature of the border at 18 inches below the surface was 72", and 

 that of the spring water 57°. In twenty-four hours the border was reduced 

 to 61°, or had lost 11° of temperature. At the pond water station the border 

 at the depth of 18 inches was 78°, and the water itself 74°. In twenty-four 



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