198 THE KITCHEN-GARDEN. [chap. vix. 
with good rich garden mould to the requisite 
depth, varying in some instances according 
to the kind of tree to be grown in it; but in 
all cases thoroughly pulverized, so as to offer 
no obstruction to the passage of the roots. 
When the trees are planted care should be 
taken to raise each on a little hillock, at the 
point of junction between the trunk and the 
root, to allow for the sinking of the ground. 
The collar of a ligneous plant should never 
be buried; as any moisture collected round 
this tender and indeed vital part, brings on 
canker, and innumerable other diseases. All 
fruit-trees thus treated produce cankered 
and deformed fruit, and die in a few years of 
premature old age. 
It can never be repeated too often that 
the essential point in growing fruit-trees is 
to keep their roots as near to the surface as 
possible, and never to suffer them to descend 
so deep as to be out of the influence of the 
sun and air. Many persons unacquainted 
with vegetable physiology, have an idea that 
when a fruit-tree, which has been productive, 
suddenly ceases to bear, it is because its 
roots have reached the gravel, or in other 
