hy LiindleT/s Theory of Horticulture. 427 



run to powder on the surface, and get covered with moss ; this 

 is what is technically called worn out: the particles will not keep 

 properly asunder, and the ground requires to be trenched, the 

 old surface buried, and a fresh surface brought up; or, where this 

 cannot be got done, where the bottom is bad, to be sown down in 

 grass. In preparing the ground therefore for seeds, if small, we 

 must break the soil into as small particles as possible, and do so 

 in dry weather ; if heavy rains occur before the particles are dry, 

 the surface is diluted into a paste, which with the next drought 

 consolidates into a crust, impervious to heat, and if the surface is 

 left rough and lumpy, the heat and moisture are not retained at 

 the surface, which is prejudicial to small seeds that cannot be 

 sown deep ; for larger seeds, or for rooted crops, the particles 

 may be left larger and wider apart, as the heat and air are thus 

 allowed to penetrate deeper, and the surface is not so easily skin- 

 ned. The same remarks will apply to the soil in pots or houses : 

 it must be kept open to retain heat, and if the temperature is 

 properly lowered in the house in the evening, we will have all 

 the advantage of a bottom heat superior to the colder atmo- 

 sphere, and thus imitate the natural tropical climate. We also 

 see the benefit of keeping the soil open about the roots of large 

 trees : the roots iret the benefit of the heat and air, and will not 

 incline to rise so near to the surface; but if the earth is kept 

 solid, they will naturally incline upwards. Stirring the soil in 

 fruit-tree borders should be beneficial, if cautiously done ; if the 

 smaller roots only are cut, it is like pruning the young wood of a 

 tree, it stimulates to the greater production of fibres ; if large 

 roots are taken away, it is like pruning large arms of the tree, 

 hurtful. 



The soil may also be kept open by other means. Manures, and 

 all other substances that decompose in the ground, leave inter- 

 stices by their becoming of less bulk ; and this is one of the great 

 benefits to be derived from manures. The opening of the soil 

 may be carried too far ; if the manure is very strong, and not 

 sufficiently decomposed, and the weather dry, it may have bad 

 effects ; but if so far decomposed as that it will divide like turf, 

 it is a source of great benefit in keeping the soil open, and re- 

 taining moisture, independent of the food it contains : this keep- 

 ing of the soil open is the great benefit derived from mixing turf 

 in composts, and from mixing pieces of moss with the soil in the 

 act of potting, which is similar ; also in mixing peat, old thatch, 

 &c., in composts. So great are the benefits to be derived from 

 decomposing turf mixed with the soil, that I recollect in the case 

 of a piece of old Scotch fir plantation, which surrounded one of 

 our nursery fields, being taken down, and the ground added to 

 the nursery ; the turf was trenched down, and so great was the 

 effects, that for some years the ends and corners of the plats 



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