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Evaluating Bud Injury and Adjusting Pruning.

Evaluate Injury in Your vineyard:  I recommend that growers collect canes and cut a sample of buds to determine whether the primary and secondary buds are alive or dead.  This is relatively simple to do, but works better if you bring the canes inside and place in a warm environment for 24-48 hours before cutting buds.  A video entitled Evaluating bud injury prior to pruning is posted at our Bud Hardiness Data page, and a detailed article, Assessing Winter Cold Injury to Grape Buds is posted online at our Cornell Fruit Pages.

Here are the steps:

  • Collect a sample of canes from your vineyard.  Choose medium diameter, well-exposed canes that are similar to the ones you would retain after pruning.  Collect enough to evaluate the first 6-8 buds from the base of the canes on 6-10 canes.
  • Bring inside for 24 hours: Place canes in a warm place, so that differences between live and frozen buds are easier to distinguish.
  • Cutting:  Use a single-edged razor blade to cut about 1/3 of the way down the bud, parallel to the cane.
  • Evaluate:  Live buds will have bright green tissue.  Dead ones will either be black/dried out (for old injury) or the color of cooked asparagus (if recently frozen).  You can, with successive cuts, evaluate the primary, secondary, and even tertiary buds.  Often the primary (largest) bud will have injury, but secondaries will be alive.
  • Percentage of Injury:  After evaluating 50-100 buds from each vineyard or portion sampled,  calculate the proportion or percentage of bud injury.

Adjust Pruning:  You can compensate for bud injury by adjusting pruning intensity.  General rule of thumb is:  if <20% of buds are injured, you don’t need to leave extra buds.  If bud injury is between 20% and 80%,  leave an additional amount of buds equal to the bud injury.  For example, if 35% of buds are injured, leave 35% more buds.  With more than 80% injury, its prudent to only remove shoots that would intrude into the adjacent vine space, to maintain vine separation.

Double pruning:  Another way to adjust pruning is to leave longer spurs or more spurs and then wait until budburst to adjust shoot number.  For example, you could leave 8-bud spurs (canes, really) and then trim them back after budburst.

Trunk renewal:  It will be prudent this year to think about trunk renewal and replacement.  Leave a few suckers at ground level, and consider training them up the trellis for replacing trunks.  Trunk injury is the ‘unknown’ factor, but typically with cold weather events one sees additional trunk injury and crown gall expression.

REMEMBER:  You can always trim off more after bud burst, but you can’t glue them back on.

For more information see:

Bud Hardiness Page

Assessing Winter Cold Injury to Grape Buds

Comments

2 Responses to “ Evaluating Bud Injury and Adjusting Pruning. ”

  • Ron clayman

    I have always started prunning where the damage is obviousand work my way up the cane until i see green wood. have you tried this/ Is it very reliable?

  • tem2@cornell.edu

    Hi, sorry for the delay, I don’t monitor the comments closely. Yes, its easy to tell where the ‘paper wood’ at the tips of canes starts, but Green wood will not tell you about bud injury, which is often a separate issue. It will tell you if the cane’s condutive tissue is viable, but not if the buds will push. Main point was that if you are expecting 50% of your buds not to push, then its better to leave extra buds, then adjust the number of shoots by pruning again after the buds push.

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