This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
This subject has of late been discussed to a considerable extent in the various horticultural periodicals. Some of the writers, notably Mr Simpson of Wortley, has been the advocate of a liberal use of the syringe during the time the Grapes are in bloom; and I at once admit that Mr Simpson's success as a fruit-grower entitles his opinion on this subject to the highest respect and consideration. Others, and amongst them the writer, think that a dry atmosphere conduces most to the setting of the shyer sorts, such as Muscats, Lady Downes, West St Peter's, Mrs Pince, Black Morocco, and Cannon Hall Muscat, inasmuch as in a dry atmosphere the pollen disperses itself with greater freedom than in a damp one. The farmer is familiar with the fact that heavy rains falling on his wheat when it is in bloom - i.e., when the pollen is bursting - is against its setting, as compared with hot dry weather; and may there not be some analogy between Wheat and Grapes in this respect? I think there is between all plants.
As to results, as far as my experience and observation have gone, I am certain that there is no difficulty in getting any Grape I know to set well in a dry atmosphere; that is, as dry an atmosphere as we find in a vinery where the steaming and watering the varieties is only suspended when the Grapes come into bloom, to be resumed as soon as they are set, except the Cannon Hall Muscat. Occasionally I have seen this Grape set well when no special precautions were taken with it; but as a rule, all I have tried with it has failed to satisfy me. Its frequent failure results from an entirely different cause to that which leads to failure in, for instance, the Black Morocco. The pollen of the former is not only deficient in quantity, but the female organ has a sort of gum over its point, which protects it from the fertilising influence of either its own or the pollen of any other Grape. Not so with the latter; the defect in its case is in the pollen. If left to the action of its own pollen, some three or four berries will set in each bunch and become a great size, while all the others remain the size of peas. On the other hand, when the bunch is in bloom, if the pollen of another variety be shaken over it, it sets as freely as any Grape I know, and swells all its berries.
This treatment will have the same effect with the other sorts I have named, the Cannon Hall alone excepted. I am not aware if the advocates of the syringe for Grapes at setting-time pretend that it will cause such a Grape as the Morocco to set in the absence of other foreign aid.
To me it appears that all that can be claimed for the system is that it does little harm; for this reason, that there is a capsule over the organs of each embryo berry, which protects them from the injury they would otherwise receive from the mechanical action of water dashed against them, until the pollen is in a fit state to be discharged on to the female organ; and seeing that these capsules come off the points of the embryo berries in regular succession, and that the syringe is used but once or twice during the twenty-four hours, it becomes very difficult to say whether good or evil is the result, though I suspect, in however small a degree, it must be the latter: certain it is that Grapes set as thick as can be desired without having the bunches syringed when in bloom, if all other necessary precautions are observed, with, as far as my own experience goes, the sole exception of the Cannon Hall Muscat; and any one who can discover a certain means of causing it to set like the Muscat of Alexandria will confer a great boon on Grape-growers.
The finest three bunches of Grapes I ever grew were Cannon Hall Muscats; they were perfect in bunch and berry, and weighed 13 lb. I got the first prize for Muscats at the July show of the Royal Botanic Society, in the Regent's Park, about twenty-five years ago: since that date, though I have often made the attempt, I have never grown a perfect bunch of this Grape, nor have I seen one; those I refer to were grown in a Pine-stove, over the hot pipes. The following and succeeding years they set so badly, that though the bunches were large enough they had a ragged appearance; and this has been their character whenever I have attempted to grow them since that date. If I were to suggest a remedy, I would look in the direction of some harmless solution that would, when applied in water, dissolve the gum on the female organs of the embryos, and as soon as they get dry apply the pollen of another Grape to them; for I am confident this gum is the cause of their failure. Wm. Thomson.
Tweed Vineyard, Clovenfords by Galashiels.