This section is from the book "The Gardener's Monthly And Horticulturist V18", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
Late, rapid growth of the pear tree, when the vitality of the leaf is not sufficient to effect a perfect assimilation of the sap, produces immature wood, which is very apt to be injured, if not killed, by' freezing, and especially by freezing and thawing, in the winter. The next spring, "the bark of the trunk and principal limbs exhibit black spots, and, on cutting into them, the bark and wood, for some distance beneath, are found quite dead and black. The only remedy is to cut away at once all of the tree that is affected - cutting below the lowest spot."
The winter of 1874-5 was a trying one to the pear trees in this region. The frozen-sap-blight showed itself in many gardens. I had two Bart-letts (standards) six years old, strong, vigorous and beautifully shaped - the result of deep, thorough cultivation and careful training. The branches on one side of one showed the blight early in the spring, and were immediately sawed off close to the stock. New branches soon put out, which I let grow three feet - as long a growth as I think prudent for pear trees to make in this climate. In a few years, by pinching back the branches of the other side and allowing them to bear fruit freely, and by manuring more heavily on the side of the new branches, and allowing them to bear no fruit, I shall restore the symmetry of the tree.
The blight struck the main stock of the other tree where it was three years old. I hesitated a week or two - harboring a lingering hope contrary to the advice and experience of horticulturists - and then resolutely amputated the stock of this cherished tree below the blight. The tree having plenty of strong branches below the point of amputation, I shall train it by spreading them in the vase form, which is preferable in some important respects to the natural form.
A handsome Duchess d'Angouleme (on Quince) was so affected by the blight that I cut it off within six inches of the ground. There are a plenty of good shoots - four of which I shall select for the base of a vase form top; three would answer.
A Buffum (standard) of the same age was killed outright.
My soil is a sandy loam, with pebbles interspersed and a porous subsoil, trenched two feet deep. The growth of the year before the blight was not large, but my treatment of the Bartletts and Duchess, I am apprehensive, was erroneous. It happening to be peculiarly convenient, I gave them a heavy top dressing of new stable manure in the latter part of the summer. Early in the spring, or late in the fall (after the leaves are off), are the proper times for manuring. Un-rotted manure I prefer to have forked in in the fall. After manuring these trees I watered them copiously with the hose, and, as the season was dry, repeated the watering into September. No extra growth followed. I submitted the case to one of the leading pear cultivators in Massachusetts, and he said the blight was not occasioned by my treatment of the trees. Yet I have my doubts. To be sure, some of my neighbors' trees, starving in the same kind of soil, with not six inches of growth that year, neither manured nor watered, were affected, and a part of them killed, by the frozen-sap-blight. It is safest never to encourage a fall growth.
In all the cases I noticed in this and the neighboring towns, every spot of blight, with one exception, was on the south side of the wood blighted - showing pretty conclusively that it was the freezing and thawing which caused the blight.
The blight poisons the sap - hence the importance of amputating immediately, on its discovery, below the affected spot, to prevent the poison from entering into the general circulation of the tree, and thereby injuring, if not eventually killing, it.
I carefully protected the spots of amputation in the cases above stated by covering them with mortar composed of clay and green cow dung, using a larger proportion of the latter. If this mortar is carefully spread and firmly pressed on, lapping over well, it will remain a year or more. When it comes off it can easily be replaced. Where clay is not accessible, loam can be substituted.