THE COTTAGE GARDENER AND COUNTRY GENTLEMAN, Eebkfauy 12, 1861. 
287 
THE SCIENCE OE GARDENING. 
{Continued from page 275.) 
Tiie canker, a? already observed, attends especially the old age 
of some fruit trees, and of these the Apple is most remarkably 
a sufferer. “ I do not mean,” says Mr. Knight, “.to assert that 
there ever was a time when an Apple tree did not canker on un¬ 
favourable soils, or that highly cultivated varieties were not 
more subject to the disease than others where the soil did not 
suit them. But I assert, from my own experience and obser¬ 
vation within the last twenty years, that this disease becomes 
progressively more fatal to each variety, as the age of that 
variety, beyond a certain period, increases ; that if an old worn- 
out orchard be replanted with fruit trees, the varieties of the 
Apple which I have found in the catalogues of the middle of 
the seventeenth century, are unproductive of fruit, and in a state 
of debility and decay.”* 
Trees injudiciously pruned, or growing upon an ungenial soil, 
are more frequently attacked than those advancing under con¬ 
trary circumstances. The oldest trees are always the first 
attacked of those similarly cultivated. The Golden Pippin, one 
of the oldest existing varieties of the Apple, is more frequently 
and more seriously attacked than any other. 
The soil has a very considerable influence in inducing the 
disease. If the subsoil be a ferruginous gravel, or a wet clay, 
or if it is not well drained, the canker, under any one of these 
circumstances, is almost certain to make appearance amongst 
the trees, however young and vigorous they were when first 
planted. 
Pruning has a powerful influence in preventing the occurrence 
of the canker. We remember a standard Russet Apple tree, 
of not more than twenty years’ growth, with a redundancy of 
ill-arranged branches, that was excessively attacked by this 
disease. We had two of its three main branches and the laterals 
of that remaining carefully thinned ; all the infected parts being 
at the same time removed. The result was a total cure. The 
branches were annually regulated, and for six years the disease 
never re-appeared. At the end of that time the tree had to be 
removed, as the ground it stood upon was required for another 
purpose. John Williams, Esq., of Pitmaston, from long ex¬ 
perience, concludes that the Golden Pippin and other Apples 
may be preserved from this disease, by pruning away every year 
that part of each shoot which is not perfectly ripened. By 
pursuing this method for six years, he brought a dwarf Golden 
Pippin tree to be as vigorous and as free from canker as any new 
variety.f 
All these facts unite in assuring us that the canker arises from 
the tree’s weakness, from a deficiency in its vital energy, and 
consequent inability to imbibe and elaborate the nourishment 
necessary to sustain its frame in vigour, and much less to supply 
the healthy development of new parts. It matters not whether 
its energy be broken down by an unnatural rapidity of growth, 
by a disproportioned excess of branches over the mass of roots, 
by old age, or by the disorganisation of the roots in an ungeniai 
soil; they render the tree incapable of extracting sufficient 
nourishment from the soil, consequently incapable of developing 
a sufficient foliage,J and, therefore, unable to digest and elaborate 
even the scanty sap that is supplied to them. 
The reason of the sap becoming unnaturally saline appears to 
be, that in proportion as the vigour of any vegetable declines, it 
loses the power of selecting by its roots the nourishment con¬ 
genial to its nature. M. Saussure found in his experiments, that 
the roots of plants, growing in saline solutions, absorbed the 
most of those salts that were injurious to them, evidently because 
the declining plant lost the sensitiveness and energy necessary 
to select and to reject. 
M. Saussure also found, that, if the extremities of the roots 
were removed, the plants absorbed all solutions indiscriminately.§ 
An ungenial soil would have a debilitating influence upon the 
roots in a proportionate, though less violent, degree than the 
sulphate of copper; and as these consequently would absorb 
soluble bodies more freely, and without that discrimination so 
absolutely necessary for a healthy vegetation, so the other most 
essential organs of nutrition—the leaves of the weakened plant, 
would promote and accelerate the disease. These, reduced in 
* Some doubts as to the efficacy of Mr. Forsyth’s Plaster, by T. A. 
Knight, Esq., P.L.H.S., &e., 1802. 
+ Trans. London Horticultural Society, vi. Art. 6i. 
t No symptoms of a cankered tree are more invariable than a deficiency 
of leaves. 
5 Saussure’s Recherches Chimiques sur la Vegetation, 260. 
number and size, do not properly elaborate the sap ; and we 
have always found that, under such circumstances, these stunted 
organs exhale the aqueous particles of the sap very abundantly, 
whilst their power of absorption is greatly reduced. The sap, 
thus deficient in quantity and increased in acridity, seems to 
corrode and affect the vascular system of the tree in the manner 
already described. 
These facts afford us most important guides in attaining the 
desired objects—the prevention and cure of the disease. 
If superluxuriance threaten its introduction, the best remedy 
is for the cultivator to remove one of the main roots of the tree, 
and to be particularly careful not to add any fertile addition to 
the soil within their range. On the contrary, it will be well, if 
the continued exuberant growth shows its necessity, for the staple 
of the soil to be reduced in fertility by the admixture of one less 
fertile, or even of drift sand. 
If there be an excess of branches, the saw and the pruning 
knife must be gradually applied. It can be only trees of very 
weak vital powers, such as is the Golden Pippin, that will bear 
the general cutting of the annual shoots, as pursued by Mr. 
Williams. A new vigorous variety would exhaust itself the 
following year in the production of fresh wood. Nothing 
beyond a general rule for the pruning can be laid down; and it 
amounts to no more than the direction to keep a considerable 
vacancy between every branch both above and beneath it, and 
especially to provide that not even two twigs shall chafe against 
each other. The greater the intensity of light, and the freer the 
circulation of air amongst the foliage of a tree, the better the 
chance for its healthy vegetation. 
If the disease be in a fruit tree, it is probably a premature 
senility induced by injudicious management, for very few of our 
varieties are of an age that insure to it decrepitude. We have 
never yet known a tree, unless it was in the last stage of decay, 
that could not be recovered by giving it more air and light, by 
careful heading-in, pruning, improvement of the soil, and 
cleansing the bark. 
If the soil by its ungenial character induces the disease, the 
obvious and only remedy is its amelioration, and if the subsoil 
be the cause of the mischief, the roots must be prevented strik¬ 
ing into it. In all cases, it is the best practice to remove the 
tap root. Many orchardists pave beneath each tree with tiles 
and broken bricks. If the trees are planted shallowly, as they 
ought to be, and the surface of the soil kept duly fertile, there is 
not much danger of the roots striking into the worse pasturage 
of the subsoil. 
Having noticed the gangrene as it appears in various forms 
upon our trees, we may now turn to a few of the many instances 
where it occurs to our fruits and flowers, for it is not too much 
to say that scarcely a cultivated plant is within our enclosures 
that is not liable to its inroads. It assumes different aspects, 
and varies as to the organs it assails, yet still in some mode and 
in some of their parts all occasionally suffer, for it is the most 
common form of vegetable disease. 
The canker in the Auricula is of this nature, being a rapidly 
spreading ulcer, which, destroying the whole texture of the 
plant where it occurs, prevents the rise of the sap. Some gar¬ 
deners believe it to be infectious, and, therefore, destroy the 
specimen in which it occurs, unless it be very valuable ; but 
this we believe to be an erroneous opinion—the reason of its ap¬ 
pearing to be infectious or epidemic, being that it occurs to 
many when they are subjected to the same injurious treatment 
which gives birth to the disease. 
It appears to be caused by the application of too much water, 
especially if combined with superabundant nourishment: there¬ 
fore, although cutting out the decaying part when it first 
appears, and applying to the wound some finely powdered 
charcoal, will effect a cure if the disease has not penetrated too 
deeply, yet it will be liable to return immediately if a less forcing 
mode of culture be not adopted. No Auricula will suffer from 
this disease if it be shifted annually and the tap root at the 
time of moving be shortened, a thorough system of draining 
being adopted, such as having the pot used one-fourth filled with 
pebbles, and excessive damp during the winter being prevented 
by proper shelter. 
" Parsley grown in a poor soil is also liable to canlcer in the 
winter. Mr. Barnes says he never found any application which 
eradicated this disease so effectually as a mixture in equal parts 
of soot and slaked lime sown over the plants. The cure is com¬ 
plete in a few days, and the vigour of the plants restored, 
indicating that this species of ulceration, like that which is 
