32 
THOMAS ANDREW KNIGHT. 
from direct injury; from sudden variations in temperature or climate; or, most common of all 
causes, from the soil in which the tree grows. Mr. Knight abundantly proved the debility due to 
old age to be a common cause of canker in every orchard.—Direct injury will also frequently give 
rise to it, whether this be produced by the accidents of wind or ladders, or by sudden alternations 
of temperature. The severe frosts of winter, acting on the insufficiently ripened wood, or a 
sudden check to growth, from a late frost in Spring, lacerate the vessels of the young wood, and 
give rise to “ canker” in the following Summer. 
The soil in which the tree grows may originally be ungenial to it; it may require drainage; 
or it may want the nutritive principles necessary for the tree ; or lastly, it may have become too 
much exhausted for the continued health of the tree. “ Want of food,” said a good orchardist, 
“ I have always found to be the cause of canker, and the same may also be said of the woolly 
Aphis. My young trees in the hedge rows became badly affected with canker, and it occurred to 
me that the thorns took the nutriment from their roots. I fed them with a dressing of lime, 
cowdung, and fresh mould, on the surface of the ground. This soon produced a good effect, and 
the trees recovered their luxuriance. I have never let my trees want it since, and am always 
rewarded by their healthy condition, and abundant crops.” 
Writing in 1819, Mr. Knight himself stated from his experiments in former years, “he had 
found that the destructive effects of canker were greatly prevented by digging up the trees once 
in every three or four years and applying some fresh unmanured mould of good quality to the 
roots ” \Hort. Soc. Trans. Vol. iii. p. 338). 
In many soils, it is well known that fruit trees can only be made to flourish by planting 
them on good soil, with a layer of paving stones, or a bed of concrete beneath, so as to prevent 
the roots reaching a soil below, that would quickly kill the tree. 
It is found that “canker” will attack seedling apple trees on the one hand, and on the other 
it is well known that many of our old varieties of English apples have long withstood its ravages. 
The Pearmain and the Costard apple have been known from the 12th century : and those old 
varieties, Catskead, Winter Queening , Golden Pippin , London Pippin , Leather coat, are still propagated 
with success by grafting. 
The valuable cider apple, the Foxwhelp may be given as an example. Mr. Knight himself 
said of this apple, more than 60 years since : “ Some attempts are still made to propagate it, but I 
“ venture to predict they will not be successful: for the grafts necessarily partake of a life that is 
“two centuries old, and the young stock can give nutriment only, not new life.” (Pomona 
Herefordiensis.) 
This unfortunate prediction beyond doubt tended greatly to fulfil itself, for Mr. Knight’s 
reputation as a practical orchardist was very great, and quite sufficient to put a stop to further 
attempts for a long time. It is however beyond question, that several of our best fruit growers 
are now propagating successfully the Foxwhelp apple by careful grafting; and the young trees 
are doing, and bearing well, so that generations to come may still hope to enjoy its celebrated cider. 
The notion that a graft can live no longer than the tree from which it is taken, seems to rest 
upon the assumption that the new wood, which proceeds from the graft, is not a new tree, but only 
a detached part of the parent. But this is evidently a mistake. A branch produced by a graft is 
