Feb
05
2009

First Cuts

A note for Internet Explorer users

Grape growing throughout the world is a challenging endeavor.  Grapevines, being a perennial plant, are not replanted from year to year and this has implications for the farmer.  Annual crop rotation is a good pest management tool.  Those bugs and diseases that attack last year’s crop might not thrive as well with this year’s planting.  You keep shifting the ground beneath the critters and they don’t  go forth so easily and multiply.

Pest management is one challenge to growing perennial grapevines; the weather, specifically the winter (which we in the Finger Lakes have in spades), is another.  Grapevines have to ride out the winter as best they can.  Generally the varieties planted can withstand fairly harsh winter conditions, but each variety has a different level of cold tolerance.  While it is hard to kill a grapevine, it is easy to make them unproductive.  Cold weather, specifically sub-zero weather, can damage grape buds, and the shoots, leaves and most importantly the fruit emerge from these buds.

One of the tasks we perform in the winter is pruning.  Most of the growth from the previous year is pruned away, leaving (hopefully) fruitful buds that produce a crop that is small enough to ripen for high quality wine and large enough to be economically viable. Before we prune though, we assess the vineyard for winter injury, specifically we test bud mortality.

To determine whether a bud is live or not we have to take a representative sample of canes throughout the vineyard and test the buds on each one.  We do this by cutting the bud horizontally with a razor (top picture).  The razor cut exposes the bud and we can visually see if it is alive or dead.  The second picture below is a picture of a live bud and the bottom one is a picture of a dead primary bud (black) and a live secondary bud (the vibrant, green, crescent below it). We then compare the number of live and dead buds and prune the vineyard accordingly.  If there are 25% dead buds and the vineyard is pruned to leave 60 buds/vine or four 15-bud canes, we leave an extra 25%.  In other words we prune a vine with an extra 15 buds/vine, which works out to four 20-bud canes.

There is science to pruning but there is also art and just as importantly, commerce.  These bud mortality numbers are an important parameter to keep in mind but the art comes in, as our winemaker, Jim Zimar says, by looking at what the vine is telling you.  Four 20-bud canes will be a starting point but every vine is different.  If a grapevine has four canes that are as thick as a man’s thumb, then the person pruned that vine too heavily and, conversely he or she left too many buds, if those four canes are spindly and weak.  The science only provides guidelines. The pruner’s art is recognizing how and where those guidelines fall within the individual vine’s growth and commerce wants that recognition to be expeditious.

Grapevines care nothing (if they care at all) about commerce, art or science. They have evolved a complex bud system with primary, secondary and tertiary buds to ensure their survival.  The secondary and tertiary buds are not as fruitful as the primary buds.  The grapevine won’t produce much, if any fruit if the primary buds are killed but, the secondary and tertiary buds, if they survive, will ensure that the vine stays alive and able to pass along its DNA in a another year.    Ultimately, that is the only thing a grapevine cares about, making other grapevines.

Jim Zimar tests vignoles buds for winter injury

Jim Zimar tests vignoles buds for winter injury

An example of a live vignoles bud.

An example of a live vignoles bud.

A dead primary and a live secondary bud below

A dead primary and a live secondary bud below

Written by Tom Prejean in: Wine and Grape growing |

2 Comments »

  • bob wright says:

    I’ve been working for a winery for 11 years and have been surrounded by the business all my life. It never occurred to me how involved trimming was. I always thought it was a bunch of people who liked to test the environmental limits of their Carharts out there hacking and whacking. Not really but, seriously very informative. Please keep educating me.

  • Jeff says:

    fascinating stuff.

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