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.
What has just been said about hard firing in the case of Pines is applicable to Vines that have been started a month or six weeks ago. Avoid high night-temperatures, and make the most of sun-heat by day. Vines now bursting into leaf will make weakly wood, with long joints and thin yellowish leaves, if forced hard at night when the nights are long and cold. Fire-heat is a necessary evil, but when accompanied with darkness the evil is much aggravated. Therefore let the chief of the firing be done by day with light. Where Grapes are wanted early, a night temperature of 55° when cold, to be run up by day to 70° or 80°, according to the aid derived from sun, is sufficient. An amount of moisture must be put into the air to counteract the parching effects of the fire-heat, but no more. Avoid steaming from hot pipes as a great evil. Stop the young growths two joints beyond the best bunch, and tie them down before their points touch the glass; but do not attempt to bring them to the wires at once, or they may break off. In thinning off superfluous branches leave the most compact and shortest-stemmed ones. When the young growths are broken about an inch, do not raise the night temperature much, but take advantage of sun-heat by day to make up for the slower growth at night.
A succession-bouse may be started by the end of the month,; and as the days are longer and the sun stronger, the starting temperature may be a little in advance of that directed for early-started vines. A night temperature of 55°, with a rise of 10° or 15° with sun by day, will not be too much, unless the weather be severe and sunless, when it may be regulated at 5° less. Where there are only two vineries, the earliest may be shut up by the end of the month and the night temperature kept from falling below 50°. See that the inside borders are kept healthily moist, and that outside ones are, to say the least, well protected from frost and cold winds. All Vines started before the 1st of January should have their roots in inside borders exclusively. Prune all Vines from which the fruit is cut, and dress the wounds with styptic, to prevent their bleeding when the sap rises. If there has been any spider or thrip on them last season, remove all loose bark, scrub the Vines well with soap and water, and then dress with Simpson's Wash or Gish-urst's Compound. Regulate the temperature of vineries where fruit is still hanging from 45° to 50°, and give air when fine, but shut up closely when drizzly or foggy.
In any houses where most of the crop is cut, the remainder may be bottled, and the Vines can then be pruned and put ready for starting at the proper time. Where sites are being prepared for new Vine-borders, let the drainage be through not less than a foot of broken stones or bricks; and if the subsoil be a cold clay, the foundation should be paved or concreted, with a good fall to a front main drain, so as to make sure that water can never become stagnant or the roots get into bad soil.
Especially during the day, and when the vinery can be shut up early with sun-heat, the forcing of early Grapes from pot-Vines may now be carried on more briskly. Under such circumstances the heat may run to 80° for a time in the afternoon - the fires being quickened in time to prevent it from sinking below 70° at 10 p.m., allowing it to drop to 60° at daylight. When the weather is cold, a lower midnight-temperature is much preferable. All rapid forcing, to be successful, should be done under the influence of sun-heat. Give these a little air early in the day, gradually increasing it till noon, when it should be gradually reduced, and the house shut closely for a few hours in the afterpart of the day, and at dusk putting on a chink of fresh air, according to the state of the external temperature. Whenever the berries attain the size of Radish-seed, thin them, and avoid over-cropping: six good bunches on a pot-Vine will be much more satisfactory than a half more. Give a dessert-spoonful of Stan-den's Manure every week, and water with clear manure-water every alternate time, keeping the balls regularly moist. Thin off all superfluous bunches from advancing crops on permanent Vines, leaving bunches that are compact and short.
The night temperature all through this month is sufficiently high at 60°: unless the weather be mild, it may go to 65°, managing as regards sun-heat and ventilation as directed for pot-Vines. If the chief part of the roots are in inside borders, see that they are kept moist, and water occasionally with manure-water. Supply sufficient moisture to the air to keep it healthily moist, but avoid a steamy state of the atmosphere. Tie down the shoots of later Vines, and stop those that are still later at two joints beyond the best bunch, and the laterals at the first leaf. Start succession-houses, observing the conditions laid down in former Calendars. Prune all Vines from which the Grapes are cut, dressing all wounds with styptic, cleaning and otherwise putting all connected with them in a state ready to be started when the time for it arrives. Examine Grapes that are still hanging on the latest Vines, removing all berries that show signs of decay. Keep the house dry, and the temperature as steady as possible at about 45° at night. Any that are bottled in fruit-rooms should also have a steady temperature and dry atmosphere, and the bottles kept full or nearly so of water.
Put the requisite number of Vine-eyes into heat about the 10th of the month, inserting them singly in 4-inch pots, plunging them in a bottom-heat of 80°, in a light pit, in a temperature of 60° to begin with.
 
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