So far in 2013 we have experienced a reasonably good winter for grapevine survival. Current bud survival number are good and from upcoming forecasts and work by Brock University and KCMS (Ker, Willwerth and Brewster) show that vine hardiness levels are very good for the next while.

It is highly recommended that while you are doing pruning in 2013, you regularly check out the CCOVI website to see the latest status for bud survival in your area.

Some quick refresher points need to be made:

  • Prune vines according to hardiness — that is hardiest vines first with most sensitive vines at the end of the pruning season (labrusca then hybrids then vinifera)
  • Generally, for vinifera vines most sensitive appear to be Merlot, Sauvignon Blanc, Pinot Noir and where possible should be the last pruned.
  • Vines that are pruned earlier in winter often will break bud in the spring earlier than the same vines pruned later in the dormant period
  • If pruning sensitive vines early, leave extra canes ("kicker canes") to hedge your bet against late winter bud injury.
  • Prune with an objective — and be aware that if you had issues the previous year (excess crop, excess bull wood or spindly growths, too dense a canopy, spray coverage issues, etc.) you will need to modify your approach to
    pruning.

There are some fundamental rules followed around the world for vinifera grape production:

  • Balance — the amount of wood and buds you leave behind should match the training system used, and allow for the vine to properly mature the crop being carried.
  • 80 to 90 % of one year old wood is removed during the dormant pruning.
  • Prune to around 12 to 15 buds per meter of row length (5 buds per foot) to allow for proper shoot spacing. Again, this is dependent on vine vigour and capacity.
  • If using pruning weight approach, this is about 5–10 kg of fruit per kg of pruning weights depending on vine capacity and cultivar or 0.2–0.5 kg of wood per meter of row length.
  • Larger vines can have higher bud count numbers than smaller vines.
  • Proper pruning early should allow for easiest manipulation of canopy later (especially crop load adjustment/thinning) including shoot positioning, hedging and fruit zone leaf removal where it is needed for premium grape
    production.
  • When in doubt at pruning - leaving slightly more buds/nodes is better than not enough. (Ker's Rule — it is easier to cut something off a vine than it is to try and glue it back on later!)

There is much debate about bud numbers and wine quality. There is a misconception that low yields always means high fruit quality. This myth has been disproven by published research around the world! Properly balanced vines always produce superior fruit to those with too little or too much crop. Crop load is regulated by pruning first and then by cluster thinning. Over-pruning (leaving too few buds/nodes) can be just as bad as under-pruning (too many buds/nodes) and lead to having to undertake very expensive time and labour to correct during the growing season.

The objective is have a balance of just enough vegetative growth to properly grow shoots and mature the fruit to optimum levels without having to undertake excessive amounts of in-season corrections (multiple times for crop thinning, hedging or leaf removal!).