Grape Are Flowering

Always a bit of a surprise on something each year. Maybe the grapes ripen earlier, higher sugars or acids, maybe some more fungal pressures or weed growth...

After near 20 years of tracking all this you'd think the weather and heat accumulations would start to pattern out where you could say when and what might happen with something close to a bullseye. Not the case and just hitting the target alone seems to be a good goal.

This year we've had a few things that are a bit anomalous. The first was a late spring hard frost that hit in late April taking temperatures to -5c or more. The buds were swelling already some at wolly stage, especially on the south facing ridges, and that cold was enough to kill those buds that were emerging.

We've also seen average temperatures at the vineyard for May and June with no hot spells and quite a bit of rain. In years gone by this means flowering in the last week of June, but we are seeing lots of flowering as of June 15/16 so we are about 1 week early with good vine growth.

So why in an average year of temperatures are we seeing earlier flowering? ...Its not the average, but the daily high-low that is making the difference and here is how...

Our average daily temperature in June is about  16c. So if we have a day with a high of 26c and a night time low of 6c our average is 16c (26+6=32/2=16). 

On the other hand a daily high of 22c and night low of 10c also provides an average of 16c...but here is the difference. Grape vines shut down or significantly slow thier growth at temperatures below 8c so when that occurs the vines growth is held back. This 8c is approximate and changes with grape varieties but for our hybrids this is usually.

So if night time temperatures stay above this 8c (+/-) the cellular growth continues even though its night time and the growth stages advance faster.

In most years our night time temperatures in June are lower than 8c which then limits the growth, but this year we've been having more rain and with that we see lower day time temperatures... but because of the cloud cover, weve had higher night time temperatures - keeping the temperatures often above 8c  and hence the growth and earlier flowering.

Pretty cool for this to happen and to be ahead in vine development but rainy weather is not good for flowering time so now we are hoping for sunny days in the next few weeks.

Changing Pruning Style - Spurs to Long Cane

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

Generally in crop load adjustments that take place after bud break and early cane development, the canes that come from the basal bud and the secondary buds are removed - but they can get missed in the adjustment.

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.