Now is the time of year to head into the vineyard and grab a sample of pruning weights. Larger growers will already be well into pruning. But smaller growers in our region can, and should, wait until as late as possible to prune their vines as this is a way to delay budbreak in an attempt to lessen the risk of early season frost damage to young buds and shoots. I won't be pruning in earnest until mid-March. Our early budbreak happened last year around March 30, so this is the last two weeks of the pruning season. I can afford to wait until the last minute with my small test vineyard.
Pruning weight samples can be taken before you start your serious pruning push, however. If you get this task out of the way, you won't have to worry about it slowing you down later.
You will only need to prune a small random sample of vines to get an average pruning weight. In order to take this measurement you will need only two items in addition to your pruning shears: a bungee cord and a small, hand held fishing scale.
What you need to do first to get this measurement is prune vine down as you normally would. Maybe be conservative and leave some extra buds so that you can trim the vines down later to keep it in balance with the other vines in your vineyard. It's always easy to remove buds down the road, but up to now I've heard of no way to add buds to a pruned vine.
Next, bundle up all of the trimmings from that one vine and wrap them with the bungee cord. Hang the bundle on the fish scale and note the weight. That's all there is to it.
Once you have your measurements, write them down in your permanent record. You will be able to compare your pruning weights from year to year, and from bloc to bloc of the vineyard. You can then use those pruning weights to guide your decision of how many buds to leave on each vine in the vineyard. Most extension programs and growing guides offer suggested pruning formulas that tell you how many buds to leave that season based on your pruning weight.
I recently weighted my Nortons and came up with an average of 3 lbs of cane prunings. The suggested bud count formula for Norton is 50+10. The first number in that formula refers to how many buds should be left for the first pound of prunings. The second number indicates how many buds to leave for every additional pound of prunings. So for 3 pounds, I should leave 70 buds on every Norton vine. That could be 14 5-bud spurs, or 25 2-bud spurs or any combination that arrives at a total of 70 buds. Every vine is a different creature.
You will find out if this formula works for your trellis system and vineyard site. You might need to adjust it once you see how it works for you. Maybe you'll find 70 buds is to many. Maybe you'll find that it's not enough, especially if you have wide spacing or a GDC trellis. Maybe next year you'd want to try 40+10 on Norton and see what the difference is. But at least you'll have a baseline to begin with.
Here are formulas for other varieties that I grow: Chambourcin 20+10, Vidal 15+10, Traminette 20+10, Cabernet Franc & Mourvedre 20+20.
There are a number of reasons to perform this measurement. It gives beginners an idea of where to start. It gives you a way to begin to predict the next upcoming harvest and growing season and evaluate what impact freeze events and damage have had on the health and vigor of your vine.
Here's more info on balanced pruning: