This section is from the book "The Gardener V3", 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.
Where the earliest crop of Grapes is the produce of Vines in pots, they will in many cases be ripe this month; and as soon as ripe they require, of course, a change of treatment. They will - especially if the pots are plunged - not require so much water, as neither the fruit nor matured foliage can make use of so much. They require just sufficient to keep the fruit "plump" and the foliage healthy - a superabundance will give watery Grapes. The house will require to be kept cooler and drier than when they were being forced on; and while cold currents of air must still be avoided, a little air must be left on all night, in amount sufficient to prevent moisture condensing on the fruit. Crops that have arrived at the colouring point should have a decreasing supply of moisture in the air, and an increasing amount of air as the colouring and ripening processes go on. It often occurs that red-spider appears on early-forced Vines just at the time of colouring, and this pest must be sharply watched and vigorously put down. The most effectual remedy is to sponge the leaves wherever it makes its appearance: an active man with a sponge can soon go over a vinery in this way. The pipes may also be coated with sulphur, and a little extra heat applied for a few nights in succession.
Syringing should only be resorted to as an extreme measure, as it is a remedy that can seldom be applied without disfiguring the fruit, to say the least of it. Where the roots are mostly inside, as should be the case in all very early-forced Vineries, red-spider is not unfrequently brought on by the roots being allowed to become too dry; and just as the first signs of colouring appear, a good soaking should be applied, and a slight mulching of horse-dung, such as an old mushroom-bed, applied regularly over the bor-der. Succession-houses that have been thinned, and in various stages between that and colouring, may now be pushed on with much less fire-heat than in the dull short days of very early spring, and they may therefore be kept somewhat warmer: 70° during mild weather, and 65° when very cold at night, should be aimed at in the case of Hamburgs and vineries with a mixed assortment of Vines. When the days are bright, keep the fires low, and make the most of the sun's power by shutting up early in the afternoon, starting the fires just in time to prevent the heat from sinking below the proper temperature at 10 p.m. In proportion as the days are long, and with more light and air, the moisture in the air may be increased, avoiding, by every means, a damp stagnant atmosphere, the evil effect of which will manifest itself by a rough wartiness in the under-sides of the leaves; and if accompanied with a low temperature, a far worse scourge in the shape of mildew.
Look over the Vines twice a-week, and remove all lateral growths as soon as they appear. In case the inexperienced may not understand what I mean by this, I wall so far explain by stating that the shoots being stopped at two joints beyond the bunch before the young shoots are tied down, and that the lateral growths on said shoots are stopped just at the first leaf. This leaves the large main leaves on the shoots, and one leaf on the lateral growths, which start from every joint of the main shoots. These give as many leaves as can find room to grow without too much crowding, and the Vines should not be allowed to ramble beyond this growth. To allow them to ramble, and then all at once remove the growths, is bad practice, and should be avoided; unless, indeed, it may be allowed to a limited extent when the fruit is stoning. Thin succession-houses as soon as the berries are about the size of a Radish-seed, at the same time removing all superabundant bunches and thinning all free-setting sorts sufficiently at the first thinning. Muscats coming into bloom may have the heat raised to 75° during mild weather at night, until fairly set.
Cultivators recommend different courses by way of getting Muscats to set; but it may safely be said that a rather high temperature, with a free circulation of air when in bloom, is the most generally practised with success, and under such treatment I have never seen a failure. Late vineries should not be retarded much beyond the first week of April. Where there are any Grapes still to cut, they should no longer be left hanging, but cut and kept as recommended in last month's "Calendar," or as recommended in our present issue by "C. K.," minus the ice now, we hope. Where the borders of late houses have been kept dry inside, let them have a good soaking of tepid water; the surface being first stirred up and left somewhat rough, or water will not penetrate freely nor regularly. See that newly-planted Vines do not suffer for want of water, and rub off superfluous buds as they break.
 
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