62 PBAGTIGAL GUIDE TO GARDEN PLANTS 



Loam is a well-balanced mixture of clay, sand, and humus, and is 

 termed ' sandy ' or ' clayey ' according as one or the other predominates. 

 For garden purposes a loamy soil is best, as it can be most readily 

 cultivated to suit the majority of plants. 



Chalky or Limestone Soils are those in which chalk or limestone 

 is present in appreciable proportion, say over 20 per cent. The 

 presence of lime may be detected by adding vinegar or any other weak 

 acid to the soil. If the lime is present in any great quantity it will 

 cause a froth, owing to the carbonic acid being released. Wet chalky 

 soils are as bad as clay, but in a hard state the particles are of great 

 benefit in keeping the soil open, and preventing the accumulation of 

 noxious acids in it. For this reason lime (or strictly speaking carbonate 

 of - lime) is added to wet sour soils to drive off the carbonic acid gas, 

 which is injurious. Peaty soils by its aid and good drainage may be 

 rendered more or less fertile in time. Clayey soils by a similar process 

 are brought nearer the ideal of what is required for the grovrth of 

 plants. 



Although lime is a great fertiliser of the soil and is always more or 

 less essential in one form or another for a large number of plants, it is 

 however injurious in the soil in which Bhododendrons, Azaleas, 

 Kalmias and certain other plants belonging to the Heath family 

 (p. 574) are grown. 



Vegetable Soil or Humus contains an excess of organic material — 

 that is, something which has been in a living state at one time either as 

 plants or animals. This kind of soil, recognised by its dark colour, 

 readily absorbs and retains water. It is useful for light sandy soils, 

 which it binds more closely ; and for heavy soils, which it renders more 

 porous. It also has the power of retaining plant foods to a great degree, 

 and by its slow decay or rotting generates carbonic acid gas, which is a 

 powerful dissolvent of mineral matters in the soil. 



Wherever organic decay or rotting takes place heat is generated, 

 and this is well instanced by farmyard manure, leaves &c. ; and when 

 this heating process takes place in the soil, the latter becomes changed 

 and rendered more fertile, and also warmer as a consequence of the 

 fermenting processes which have taken place. 



Humus, although very valuable, is not alone a suitable medium in 

 which to grow plants, being too light, spongy and loose, and devoid 

 of much mineral matter. It is most useful in conjunction vyith the 

 other soils, and is chiefly obtained from farmyard manure, and the leaves 

 of trees. The latter should be collected every autumn and stored in 

 heaps. The action of the weather, rain-water, and an occasional 

 turning over will soon reduce them to what is termed ' leaf-mould.' 



