376 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
[ Ottofter 25, 1888. 
Pears. 
Uvedale’s St. Germain .. 
Van Mons. Leon Le Clerc 
Verulam .. 
Vinense .. 
Williams’ Bon Chretien 
!> J» „ 
Winter Nelis . 
Exhibitor. 
Messrs. J. Cheal & Sons. 
Mr. R. Smith. 
Messrs. Saltmarsh & Son. 
Royal Horticultural Society. 
Mr. R. Smith. 
Mr. T. Richardson. 
Mr. H. G. Oclee. 
CANKER IN FRUIT TREES. 
By Edmuxd Tonks, Esq., B.C.L., Knowle, Warwickshire. 
I have been requested by Mr. Barron to contribute a paper for 
discussion at this meeting, and as the results of some experiments 
recently made by me appear to indicate that there may be a remedy 
for that worst of all diseases affecting fruit trees—canker, which is 
described in the “ Herefordshire Pomona ” as “ the terror of all 
orchardists and the bane of most orchards,” I thought it right to 
comply with the request. As my own experience scarcely extends 
beyond my garden, and numerous duties hare prevented me from 
devoting even there that close and continued observation which is 
necessary for the proper study of such a subject, I should have hesitated 
to intrude my crude notions in antagonism to the authorities if their 
views had been clear and definite ; but as these are very vague, both as 
to the cause and the cure of the disease, I venture to state my own. 
Thompson, in the “ Gardener’s Assistant,” says —“ The cause is im¬ 
perfectly understood, and so consequently is an effectual cure Mr. 
Fish, in “Cassell’s Popular Gardening,” says—“ In fact it may almost 
be said to be incurable and the “ Dictionary of Gardening,” the 
most recent publication on the subject, says —“ Were the causes better 
known, the remedy might generally be much easier found.” Yet these, 
and most of the other writers on the subject, according to my idea, 
indirectly indicate both the cause and the remedy for the disease, the 
cause being mal-nutrition, the consequence of an imperfect provision in 
the soil of the food required by the plant; the remedy, the supply of 
the food which is deficient. These writers inferentially indicate this 
remedy. For instance, Thompson recommends that “ the soil be 
ameliorated, by trenching and other means Mr. Fish, in “ Popular 
Gardening,” says—“Lift the roots into higher places of warmth, and 
better and more immediately available supplies of foodand the 
“ Dictionary of Gardening ” says—“ Trees that are badly cankered may 
be improved by lifting and replanting in improved or better drained 
soil.” 
Perhaps the most convenient method of dealing with the subject 
in detail is to analyse, paragraph by paragraph, all that is stated relating 
to canker by some recent and recognised authority; that splendid 
work, the “ Herefordshire Pomona,” is possibly the best for the pur¬ 
pose, as it may be assumed to contain a summary of the most recent 
knowledge of all that relates to orchard growth. The first paragraph 
of the passage in that work relating to canker states that “ it is 
always due to direct injury.” In a controversy a clear and definite 
issue is most satisfactory, therefore with all submission I venture to 
assert that it is never due to such cause. That canker may appear in 
parts which have been injured is no proof that the injury caused the 
canker, although the injury may determine the particular spot where 
the disease makes itself visible. A well nourished and consequently 
healthy tree may be injured to any extent without development of 
canker, while an ill-nourished tree, or, to avoid begging the question, a 
tree infected with the disease, will develope in all parts the external 
signs without the slightest injury or abrasion of any kind, and very 
frequently on parts where, from their well-protected position, such as 
the angles of the branches with the main stem, it is almost impossible 
that injury could take place. The coincidence of canker and an 
injured part is no more proof of the former having been caused by the 
injury than that a hole in a building through which the flames of a 
conflagration are first visible is the cause of the fire. 
The second paragraph states that “ weakness is at the bottom of the 
C5”kcr.'’ This weakness cannot be want of apparent vigour of growth, 
for I have frequently observed trees attacked which for a number of 
years have made the strongest growth, yet the disease has appoared 
before any external signs of weakness were visible ; the very vigour 
of the growth in some cases appearing to hasten the attack in a soil 
containing too limited a supply of the necessary food, as that supply 
is sooner exhausted, and the time arrives when the large tree can no 
longer find within reach of its roots sufficient for its maintenance. It 
may be that only one element of food is failing ; but every element is 
indispensable for perfect growth of the whole tree, and that failure 
would fully account for arrest of growth in parts, weakness, and con¬ 
sequent disease. 
The third paragraph is “ the tree is old.” This may bp expressed in 
other words—the tree has for a long time been growing in the same 
soil. It is not difficult to realise that in the course of many years a 
tree may exhaust the most fertile soil. Many seem to overlook the- 
necessity of restoring to the soil what is taken away year after year by 
large crops of fruit. However rich the soil may have been originally, 
each crop takes away a definite quantity of the food required by the- 
tree, until in time insufficient remains ; then the tree falls, not through 
age, but through inanition. The same gardeners who leave their fruit 
trees unfed would think it most unreasonable to expect them to grow 
their crops of vegetables without manure. 
The fourth paragraph is, “ or the variety is very old or very 
delicate.” This raises the much-vexed question whether a seminal 
plant has a finite life, or one which can be prolonged indefinitely by- 
propagation. Experience seems to prove that individual life has a 
limit, though there is evidence that many seminal plants have a very 
prolonged existence ; however, the limits of this paper do not allow 
the present discussion of the question. It may be sufficient to say 
that observation does not lead me to believe that the age or delicacy 
of a variety renders it more liable to canker when the soil contains- 
what it requires. 
The fifth paragraph suggests “ that the soil is not sufficiently- 
drained.” Canker, according to my observation, occurs equally on 
well-drained as on ill-drained soils ; it is not a question of condition 
of roots. My own garden formerly contained several trees rapidly suc¬ 
cumbing to canker, which, when grafted with other varieties, at once 
put on healthy growth, made fine heads, and have since for many years- 
been perfectly free from the disease. Each variety requires its own 
appropriate food ; Strawberries afford a very good illustration of this— 
I have among my friends the reputation of growing this fruit to per¬ 
fection, yet I had the greatest difficulty in finding varieties which 
would do fairly in my soil, and after trial of many more than a hundred,, 
have so far discovered only about half a 'dozen which are moderately 
successful. British Queen refused to fruit ; Dr. Hogg bore fairly as 
an annual, but did not survive to the second season; in fact, all the 
Queen race and many other kinds only do more or less ill. Such- 
being the case, it is not unreasonable to believe that some varieties of. 
fruit trees find in some soils what they require, while others do not, 
and in consequence become subject to canker. 
The sixth paragraph is, “ or it (the soil) may be too poor.” I quite- 
agree with this, as I believe a deficiency in the soil of the necessary- 
food of the tree is the cause of canker. 
Seventhly, “ The wood may be weak, and is not well ripened, when, 
a sudden frost, especially after rain, ruptures the vessels, and this 
forms the chief cause of canker.” Unripe wood, which is, however >• 
often the result of imperfect nutrition, is productive of much mischief 
of a temporary nature ; but as canker attacks well matured wood, L 
cannot believe it to be in any case its cause, although when the real 
cause is at work it may appear on such wood. 
In the eighth paragraph the author repeats himself. “Any direct 
injury, however, to the bark of a tree as from friction of one branch 
upon another, the pressure of a clothes’ line tied from tree to tree, or 
injury from a ladder in fruit-gathering, may all cause it even in 
healthy trees.” This calls for no further reply than that given to the. 
first paragraph. 
Finally, the author states that “ Canker commences with an en¬ 
largement of the vessels of the bark, more apparent, by the way, in 
Apple than in Pear trees, and continues to increase until in the course 
of a year or two the alburnum dies, the bark cracks, rises in large 
scales, and falls off, leaving the trunk dead, and ready to break off 
with the first wind if not before removed. The canker shows itself 
quickly, and if the cause be sought for it will often admit of a remedy. 
The most usually effective is a good supply of nourishment to the trees- 
affected, together with the removal of the parts injured.” I confess 
.that the preliminary symptoms described as the enlargement of the- 
vessels uf the bark have escaped my observation ; but there appears to 
be some contradiction lh the statement, as while the first symptoms of 
the disease are described as extending over a year or two, further on it 
is stated that canker shows itself quickly. However, although I differ 
so much from the writer of the article in the “ Pomona ” as to the 
