VINE-CULTURE UNDER GLASS.

New Zealand Journal of Agriculture, Volume 53, Issue 3, 21 September 1936, Page 156

VINE-CULTURE UNDER GLASS.

f Continued.)

J. C. Woodfin,

Manager, Horticultural Station, Te Kauwhata

The Treatment of Established Vines. Climatic conditions vary so greatly in different parts of New Zealand that treatment which would be correct in one part is quite wrong in another.. The climate of Auckland, some parts of Hawke's Bay, and of a few other localities is essentially different from that prevailing in the South Island and most parts of Wellington and Taranaki. It is evident that, in places where in summer the climate is almost tropical, more ventilation is necessary than is the case in cooler districts. It is a fact that the grape-vine will thrive in places having a much higher .average temperature than is recommended for its culture in standard books on the subject. There is, however, a limit, and when the temperature under sun-heat rises much above 90° F. any further rise must be checked by increased ventilation. In most places where grapes are grown a much lower mean temperature prevails than is the case in the few warmer places mentioned. In general practice it is inadvisable to make use of the bottom ventilators before the berries begin to colour. The effect of admitting bottom air while the foliage is wet has already been explained. In that case, however, young vines were being dealt with, a very different matter to that of established vines carrying a crop of fruit. Vines in full foliage and carrying fruit always hold more or less moisture on their surfaces. This is the case even where damping-down is of a minimum character, and there is danger in admitting bottom air if the outside air is appreciably colder than that inside the house. In warm districts and during calm weather this condition would not be present, therefore no harm would result from the use of the bottom ventilators provided obvious moisture had been first dispersed. It is rare to find in this country vineries that are absolutely airtight. In most houses there is some space between the bottom pane of glass in each run and the sill; and this is a good feature, worth securing in all but the coldest districts. Air entering through these spaces passes up between the leaves and the glass. It has very little effect on the temperature in the house, but vastly improves the texture of the leaves, making them firm and leathery, a very desirable condition. BEARING LATERALS. The universal practice in the cooler districts is to leave only one lateral to each spur. Commercial growers usually train the rods more closely together than is the custom with private growers, and so secure a larger

number of smaller bunches. The system in other respects is the same in both cases. The one-lateral system is the only one by which the surface of the leaves can be properly exposed to the sun, which is a. necessity in successful culture, and must be considered so in most situations. Besides this, the attention required in stopping, tying; down, &c., is more handily given, and the suppression of pests is made as easy as possible. Circumstances do sometimes occur where a departure from the rule: of one lateral to the spur may be advisable. Cases are known where two, three, and four laterals have been left, each of which carries one or two bunches, which are well ripened. These cases are in the North/ where the climate is such as to allow liberties not possible in most other places, and the houses are very large, so that there is a good body of air ; and the borders are extensive, of the best of soil, and well fed. Though, so far successful, this system cannot be recommended for general use. In most parts it would result in failure, while the same results could, be secured by the safer plan of an increased number of rods and one lateral to each spur, which method will be followed in this series. None but experienced growers should depart from it. ROUTINE WORK. Pruning should be done in the early part of June, or earlier in warm, districts, when all the principal leaves have fallen or would fall if the rods were shaken. Pruning should not be delayed when this stage is reached ; the vines are benefited by a good rest, and, moreover, late pruning causes bleeding, with consequent weakening of the vines.. Each lateral should be cut back to the base bud, the lowest prominent, eye, cutting squarely across about | in. above the bud. It is bad practice to cut close to the eyes. If this is done, and the vines break strongly, the laterals have not sufficient foothold and are liable togrow off, resulting perhaps in a barren spur. After pruning, any loose bark on the rod should be stripped off, but bark which is not loose should not be removed. The practice of stripping off all the bark that can be removed is quite wrong : it weakens the vine and prevents the rods thickening as they should. If diseases or pests are present, washing or dressing the rods may be necessary : this is dealt with in a later section. If the rods are clean no dressing is required.

In spring the top buds have a tendency to break into growth before those on the lower part of the rods, and if this occurs the top laterals, get ahead of the others and tend to so weaken those at the base of the rod that dead spurs result. To cause an even break, after being pruned, and dressed, the upper half of each rod should be left loose, so that it. may bend down in the form of a bow, and be kept in that position until the buds on the lower part of the rods have started to grow. During the dormant period all the ventilators should be kept open ; this ensures to the vines a thorough rest. This is one of the advantages of having the house reserved for vines, for when the house is shared by other plants ventilation is adjusted to their needs and higher mean temperature is maintained, which may cause the vines to start too' early into growth in the spring. Except where vines are forced for early crops and heat maintained, it is not

■desirable to start the vines until a steady rise in outside temperature may be expected. If vines are started too early a spell of ■cold weather may cause a check in growth; which is a result to be avoided. When the time arrives for the vines to start growth the bottom ventilators should be kept closed. Syringing the rods, and so creating a moist atmosphere, is considered to assist the vines in breaking. When all the buds have broken and made a few inches of growth the rods should be suspended in their proper places. A good time to get the rods into their proper positions is when the shoots average from 4 in. to 6 in. in length. The tying-up of the vines requires to be done with care, otherwise laterals may be broken off. The risk is greater where the shoots have made much growth. The laterals rarely break quite evenly; some are more advanced than others. As recommended earlier, each lateral should be pruned back in winter to the lowest prominent eye. In all but rare instances there are other dormant buds close to the one pruned to, which, though less prominent, will in some cases break quite as strongly as the one selected. The two strongest and well placed laterals on each spur should be kept until they have advanced in growth far enough to allow the selection of the one that promises to produce the best bunch of fruit. All but these two should be rubbed off as soon as the rods are suspended in their places, or as soon as they show after that time. When the final selection has been made the spare laterals should be broken off from their base. The growth of the laterals at this time is very rapid, and, as it is highly important to prevent waste of growth, constant attention is necessary. Each lateral should be “ stopped ” at a point two leaves beyond the bunch of grapes nearest to the old rod. It may be that the second is the better bunch, and when this occurs it should be retained instead of the first. In such cases the lateral should be “ stopped ” at a point one leaf beyond the second bunch. In the case of close planting it may be necessary to stop at one leaf beyond the first bunch, so as to leave room for the extension ■of the lateral from its next break. In this case, if the second bunch is retained, stopping must be close to the bunch. This can safely be done to a limited extent, and, in fact, often is. There is no need for haste in selecting the bunches to retain; they. do not become a drain on the vitality of the vine until the berries begin to swell. It is best to wait till the berries are set, as it sometimes happens that some bunches do not set well. Surplus bunches should, however, be removed before much swelling of berries takes place. Where there is no fruit on any of the laterals on a spur, a wellplaced lateral should be pinched back to one or two leaves and all new growth pinched back to one leaf. This lateral may then be pruned back in the winter to the base bud.

Stopping the laterals should be done by pinching off the tips with the thumb-nail. It is harmful to allow them to extend so that several joints have to be removed. The removal of a considerable amount of leafage, as would result from this practice, causes a severe check to the roots, and, what is far more important, the vitality expended in producing the extended lateral growth will have keen lost. •

Tying down the laterals is at times an operation requiring great care. If the laterals are stout they are extremely brittle, and are easily broken out of the spur. To bring such laterals safely down to the wire, hold the base of the lateral between finger and thumb of one hand and follow up the lateral with the finger and thumb of the other hand, giving a twist at each node sufficient to produce a crunching sound. After two or three twists the lateral can be bent down in safety. Where the trellis is a good distance from the roof tying down may be left till the base of the laterals becomes firm, as evidenced by a yellow appearance in the bark. The leaves must be kept clear of the glass, which may make it necessary to tie down a little at a time. SUBLATERALS. The treatment of sub laterals is a subject on which there is a wide divergence of opinion among experienced growers. In former times their extension was believed to be a necessity in promoting root-action. At the present time it —and, indeed, has been for a number of years —the practice of most commercial growers to suppress them altogether, breaking them out as soon as they show. It is held that if the vines grow strongly and make large leaves the sublaterals can be dispensed with. The advantage in doing this is a considerable saving of time, and in cases of close training it allows of a free passage of air among the leaves. An even spread of large leathery leaves is infinitely more valuable than any number of small and crowded leaves. One should be able to obtain an uninterrupted view between the foliage and the roof throughout the whole length of a fairly large house. If this condition obtains leaves will not be burned through pressing on the glass, and there will be no accumulation of moisture to cause burning and mildew, while the leaves, being exposed to light and suffering no injury, will be able to perform their normal functions properly. SETTING AND THINNING OF THE BERRIES. In this country there does not appear to be the difficulty in getting a good set of fruit that is experienced in the United Kingdom. No trouble of this kind has come under my notice except in cases where the vines had been badly treated or have been grown in a wet atmosphere. Varieties such as Lady Downe’s and Muscat of Alexandria, reputed to be shy setters, have in my experience set quite freely. During the flowering-period the house should be kept rather dry not entirely so, but “damping-down” should be moderate. Somewhere about midday vines of shy bearing tendency should be given a shake or jar just sufficient to cause a movement throughout the whole vine resulting in the dispersion of the pollen. The shaking should be repeated daily while the vines are flowering. As soon as the berries are set they swell very rapidly. Surplus bunches should therefore be removed before the berries have ' swollen much, and should not be left for removal as thinning proceeds, as this would cause a waste of vitality. Varieties that are known to set freely may be thinned as soon as the blossoms fall, but shy setters should be left till the berries are the size of peas. The earlier thinning is done the easier it will be, and the better. If the berries crush each other before thinning is done the work is slow and difficult, and the berries will not afterwards attain full size.

There are different methods of thinning. The usual is] to first remove unfertilized berries, and then ease the upper and crowded part of the bunch, removing the berries in the centre, and severely thinning those on the under-part of shoulders. A start is made at the bottom of the bunch, after selecting one berry to form the point. No exact rule can be laid down as to the number of berries to remove, this depending a good deal on the variety. Berries that have short footstalks require heavier thinning than those with long. John Wright, in the “ Fruitgrowers’ Guide,” states the average

number to remove is . two-thirds on the ' lower parts of the bunch, half at the middle, and one-third at the top. . This, however, must not be accepted as a fixed rule. Experience is the only satisfactory guide. ■ Thinning is usually done in amateurs’ vineries with scissors made for the purpose, a button-hook or a forked stick being used to hold the sprays in convenient positions. Where there are distinct shoulders to the bunches these should be raised somewhat by strands of raffia fastened to the trellis. This should be done before thinning the bunch is commenced, as it permits the leaving of berries that would otherwise have to be removed, because they would be smothered by the shoulder. Commercial growers generally cut out all the loose shoulders before commencing to thin. A quicker and less' tiring method is to place one hand behind the bunch and pick out the berries with the other hand. The scissors cannot be entirely dispensed with. They are necessary for cutting diseased or damaged grapes out of ripe bunches when handling would spoil the bloom on the grapes. (To be continued.)