Pruning technique for a mature “vertical cane positioning” trained (guyot) vine

Prune every other cane back to the basal buds- these will become next years ‘renewal spurs’. The remaining canes, prune to 5 buds- these will be next years ‘fruiting spurs’ (you’ll prune these a little more later..)

then…

1.Weigh the vine’s pruned material.

2.Prune next years fruiting spurs so that you keep 20 buds per plant plus 10 buds per pound of pruned material. Each fruiting spur should have 3-5 buds and each renewal spur should have 2 basal buds. There’s an equal quantity of renewal and fruit spurs. Example: I remove 2 lb of year-old vertical canes, so I keep (20+ (2x 10)) 40 buds. I have 16 spurs per plant- 8 renewal & 8 fruiting. The renewal spurs account for (2×8)16 buds, leaving 24 buds to be divided between the fruiting spurs, which results in 3 buds per fruiting spur.

3.At bud break, snap off the weakest branch per spur, leaving one branch on the renewal spur and x-1 branches on the fruiting spur, where x= the number of buds per fruiting spur as calculated in (2) above

Alternative, simplified version:
cut the fruiting canes out totally, down to the swollen base at the bottom of the stem. Cut the renewal stems back to 3 inches to create the new spurs. Next year, allow two uprights to grow from each spur, pinch out the lower, weaker ones. Allow each fruiting cane to crop one bunch only. As the vine matures, if the growth is very vigorous you can allow more than two bunches per spur.

4.As soon as possible after bud burst, rub-out the flower clusters from the renewal cane to stop this cane from fruiting.

5.Summer pruning: each bunch of grapes needs about 15 leaves to ripen- any more and you shade your fruit, limiting its sugar content. Any less and you weaken the vine. At 4inches between each leaf, this works out roughly at 50cm of cane per bunch of grapes on a fruiting spur (based on the inclusion of leaf canopy on the renewal spur). Once the canopy reaches this height, trim it. Also trim the side branches that may grow.
So if you allow 2 bunches per spur, trim the canopy to 1m above the old wood.

6.In late summer, take off the big leaves at the bottom of the fruiting canes to allow sunlight and air to get at the fruit- all leaves below the fruit and 2 leaves above the fruit is recommended.

7.The following winter, cut this years fruiting spur down to 2 basal buds (at the very bottom of the stem, where it joins the old wood), and leave 5 buds on what was the renewal spur canes. These become next years fruit spurs.

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