153 



SUMMER TREATMENT OF GREEN-HOUSE PLANTS. 



Among the means in our power of modi- 

 fying the excess of terrestrial heat, I would 

 mention, first, by giving the soil the ca- 

 pacity of containing and retaining moisture. 

 This is done most effectually by adding 

 loam, clay, and peat, (or muck, as it is 

 called here.) These soils not only absorb 

 moisture in the greatest quantity from the 

 atmosphere, but suspend it in their pores 

 for the greatest length of time. Moreover, 

 the organic matter they contain combines 

 with the water quickly, and supplies food 

 to the plants. Secondly, rendering the soil 

 capable of supplying itself with moisture 

 by capillary power. To effect this, we 

 must trench deep, — 2, 3, 4, or 6 feet. No 

 matter how deep we go, providing we keep 

 the best soil always on the surface. All 

 substrata contain a large amount of water, 

 and sandy strata, on impermeable beds, 

 generally the greatest, as they absorb the 

 water more quickly when it falls. By deep 

 trenching, the subsoil is opened up; and 

 when dry weather comes upon us, with its 

 attendant evils, then, by capillary action, this 

 water rises from beneath, bringing with it 

 the soluble substances that exist in the sub- 

 soil through which it ascends. On this 

 point Johnston remarks : that in sandy soils, 

 and generally in all light soils, of which 

 the particles are very fine, this capillary 

 action is of great importance, and is inti- 

 mately connected with their power of pro- 

 ducing remunerating crops. They absorb 

 the falling rains with great rapidity ; and 

 these carry down the soluble matters as 

 they descend. On the return of dry wea- 

 ther the water re-ascends from the lower 

 strata, and again diffuses the soluble in- 

 gredients through the upper soil. — [John- 

 ston's Ag. Chem.] Thirdly, by the artifi- 

 cial application of water ; and by its gene- 

 ral applicability to the culture of orna- 

 mental plants, this method more particu- 



larly demands our attention. But whether 

 the plants be growing in flower-pots or in 

 the flower-garden, we cannot treat on the 

 subject of watering without, at the same 

 time, considering the nature of the soil in 

 which the plants are growing. The power 

 of soils is so different of absorbing and re- 

 taining water, that it ought to be the first 

 business of a plant-grower to procure that 

 which is most suitable. We know that 

 the best soil for soft wooded plants, is that 

 which contains the largest quantity of de- 

 composing matter; and we know, also, 

 that the coolness of a soil is just in propor- 

 tion to the moisture, or rather the organic 

 matter, it contains. This is sensibly the 

 case ; for the sandy and gravelly soils, 

 which are the hottest, are also the dryest, 

 and on that account also retain their heat 

 the longest. It has been said by some 

 authors, that dark coloured soils absorb 

 heat from the sun's rays more rapidly, and 

 attain a higher temperature than soils of 

 other colours. But this will only be found 

 to be the case when both soils are chemi- 

 cally alike ; and this is seldom, if ever, the 

 case ; for the amount of organic matter 

 which black soils generally contain, more 

 than counterbalances their superior power 

 of absorbing heat ; and they will frequently 

 be found 10 or 12 degrees below the tem- 

 perature of sandy soils, immediately be- 

 side them. On the 23d of last month, I 

 placed the bulb of a thermometer 6 inches 

 below the surface, in the soil of a border, 

 made up of black peat earth, clay, and a 

 quantity of manure, mixed together, — the 

 black soil predominating, and giving its 

 colour to the whole. After remaining an 

 hour, the mercury rose only to 93°. On 

 the same border, a few feet distant, in the 

 common soil of the garden — rather light 

 and sandy — at the same depth, the ther- 

 mometer rose in a few minutes to 104°; a 



