For a long time we've been using the spur pruning style for most of our varieties. Its a clean and easy way to prune and with a hanging curtain trellis its easy to space the canes out fairly easily. We switched to long cane for some of our varieties and had an excessive amount of pruning to clean up but we are hoping this pruning style is more productive.
Prunings gathered at the end of the rows.
When pruning you are looking for a balance in a decent crop load but quality fruit as well...to many canes and fruit on the vine and the grapes may not ripen well, too little and there may not be enough of a crop to be finacially viable. When pruning the vines you assess the amount to prune on a few factors but most its the previous years growth and crop load you are seeking (Tons per acre). The growth from the previous year gives you an idea of how many buds to retain for this year as you know from experience the vine can handle it. There are methods that are often employed in the first few years involving weighing the prunings and based on the weight you assess how many buds to leave on the vine. You can look this up but this is really a generality, as soil, inputs, fruit thinning, climate vs. ripening vs. crop load and more all play a part in this and its perhaps at best a baseline to start with. Then after you've applied that for a few years you can make a more informed judgement of how many buds to leave based on your experience.
And there are exceptions as well - a good example of this is Leon Millot, this vine will ripen clusters on very small canes and the amount of buds that you would leave on this vine based on the pruning weight would not sufficiently provide enough crop the following year...so you recognize the need to leave more buds than what a pruning weight formula would tell you and over a few seasons you figure it out.
So when leaving buds you generally count out approximately the number of buds you need to leave in the expectation that each bud produces a cane and each cane produces an approximate amount of grapes. Through this you can estimate a probably crop load and tons of grapes at harvest.
For buds counts, there is a bud that is at the base of each cane...the primary basal bud, and it often doesn't produce much for grapes in hybrid vines so its referred to as a non-count in terms of fruit production. But in terms of the number of canes the vine can support it is really important as it has no or low production but the cane draws energy from the vine. Also, most buds have a secondary bud as well and they are delayed in emergence but will produce a cane and often limited fruit in hybrids. These secondary buds are life savers when there is a late spring frost as they emerge later than the main bud and often don't get hit by the frost yet still produce a smaller crop. Image below shows basal bud - green arrow and two other buds.
2 bud spur pruning showing basal bud (green arrow) and two other buds
So for a spur pruned vine that has 26 buds spread out across the cordon arms we have 13 x 2 bud spurs which should result in 26 canes. Each of these 2 bud spurs will also have the basal bud and if left to grow there would be another 13 canes on the vine which would negatively impact the vine as these pull energy from the vine, slowing the growth and development of the 26 canes (and fruit on the canes) that we want to retain. So we would normally remove this canes that shoots out from the basal bud during our crop load adjustment.
The other canes we remove are the canes that form from the secondary buds. Generally on our hybrid vines each bud will produce a primary cane from the primary bud - which we want to keep, and a secondary cane from the secondary bud which is delayed and we want to remove. Again if we don't remove these then we have 26 more canes that will generally negatively impact the growth of the canes and fruit we want to keep.
Secondary Bud (the little one - delayed) is the one we will remove.
Removing these canes that we don't want is a shoot thinning exercise and necessary to get quality fruit and production that we envisioned through the pruning process.
For many of our vines, we've switched them this year to a long cane pruning style. In general we keep two canes per vine with this style of pruning. Each cane has about 8-10 buds on it. We bend a cane over in each direction and have retained 16-20 buds with these 2 canes. We also retain a few short spurs, 3-4 buds each in the centre of the vine to retain the 24-26 buds we want for the vine which covers 5' of trellis.
Long Cane Pruning
The shoot thinning is a bit different in this pruning style in that each of these buds on the vine will produce a secondary shoot and we will remove these as noted. But we are only retaining 4 shoots now from last year - 2 x 8-10 bud long canes, and 2 x 3-4 bud spurs and so we only would have 4 basal shoots to remove. Perhaps a bit less work, but marginally so, however, less chance of missing some of them.
Long cane pruning is considered a excellent pruning methods for alot of hybrid grapes as research has shown that some grape varieties have more fruitful buds at bud 5-8 on the cane. This is not the case for all grape vines but for several of ours this would seem to be the case.
