A VITICULTURIST 'S DIARY
Juggling crop loadings Recently during a quick trip to the UK to attend Vineyard Magazine's excellent trade fair in Kent, I got to catch up with many vine growers. There soon became a common theme to recount in our conversations; the recent harvest time and how common were juggles around crop loadings. This is a complex subject, especially since people who are considering undertaking some removal of what they feel are excessive grapes, are never in a position to know what the weather will be like in the many weeks ahead. However there are some fairly simple generalisations that are probably of good benefit to be aware of. Naturally extensive experience eventually shows itself to be the best teacher around matters of fruit thinning. Another being to hold effective talks with the winemaker to seek out a compromise in how much work to undertake, and to attempt to
deliver a balanced crop of quantity and quality of grapes, (focused towards an agreed style of wine.) The matter of quality needs to be understood and agreed between all parties if the best results are to be achieved, in much the same way as discussing issues like fungal infection on the grapes. One of the main problems to be found in the cool margins of a climate for crop growing, is that too much crop simply has not enough time to accumulate adequate sugars, and to metabolise away the acids. If you do not start thinning your crop soon enough, then you'll never get on top of any arising problems. Quite a good, and simple, exercise is to make a graph showing the effective 'growing degree days' available to you, in the final couple of months of the season. In simple terms plants are not able to function under 10°C, or in the dark! Have a look at the number of hours of effective plant activity, say, 10 days prior to the equinox, (September 21,) and compare that to the number of hours 10 days after the equinox – the equinox is the time of the fastest change of daylight hours, and once those hours, and temperatures, have fallen below a effective functioning amount there is very little that can rescue your increasingly challenged crop at this time. As readers of my previous thoughts are aware, I do not favour relying on chemical intervention in the winery. It being preferable to seek more appropriate varieties, and then consider forms of management that assists a better outcome. Simple matters to consider might include some of the following. There are some varieties, or even perhaps a 'family' of varieties, that are inclined to grow secondary shoots and on which grow a second crop of grapes. This can be found in some of the French selections of clonal material of the Pinot group, as a point of illustration. If you can, it is best to remove this second set, and earlier rather than later. They are a liability.
With some stronger growing situations or varieties, there can be what are called 'double budding' shoots along a cane. The second shoot being shorter and weaker. This will never come to much and only serves to hold back the rest of the vines, so take them off, and again early. In a similar manner a vine that is a bit short in 'over wintering reserves' of energy, can have a restricted amount of growth in some of the buds that lie in the centre of the cane. If it becomes obvious that the new shoots are slowing down in their growth, then simply 'nip off' the top flower, (or young bunch.) Likewise some people find that the two shoots arising out of the buds at the far end of a cane, might give rise to possibly three flowers. This being the case then take off the top one. (Another variation of this is to let them grow, and come a time when the acids are falling a little, and the sugars are rising – probably some time after veraison – then the top two bunches can be harvested from which to make grape juice out of.) All of the above activities can be undertaken around flowering time, or shortly thereafter. I have heard people comment that they in some form, fear the vine compensating for the loss in potential berries by multiplying the amount of cell growth in the remaining berries. Thus come veraison the berries swell up larger and the vine has less skin area in its berries relative to the volume of pulp...but I have never seen studies on this and generally feel that if over all there is a smaller, and thus better developed crop, then over all this is the best outcome to seek. It is worth noting that vines are not entirely effective in creating photosynthates in one shoot, 'translocating' those compounds down the shoot...along the cane....and then up another shoot, (with which to ripen a bunch of grapes on a differing cane from which the sugars were formed,) Yes these complex compounds are created to be reserves within the vine, and might get to power root growth, build up reserves in the trunk, or even lignify/ mature a shoot to become a cane, but in
Sam Doncaster works for Volker and Marion Freytag, of Rebschule Freytag, Lachen-Speyerdorf, Neustadt an der Weinstrasse, Pfalz ENVELOPE samdoncaster@hotmail.com
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