Viticulture 101: Pruning grapevines
Like wine? Want to better understand the winemaking process? Most winemakers will tell you that great wines start in the vineyard. So here’s your opportunity to learn more about how wine grapes are cultivated. In our Viticulture 101 series, we will explain the basics of the different growth stages, just as many of Oregon’s vineyards are experiencing them. Follow along as we walk you through the 2016 growing season.
Across the state, grape growers are working in their vineyards, preparing for the upcoming vintage. Those not planting new vines are hustling to get their vineyards pruned while the plants are still dormant. As the days get longer and warmer, the sap begins to run, and the vines awaken from their winter slumber.
Visit the Willamette Valley in late winter and you’ll hear the staccato clip of pruning sheers as vineyard managers trim away roughly 75-90% of each plant’s growth from the previous year. Only the heartiest canes growing from the trunk of the grapevine are deemed good enough to produce the new vintage so the rest are trimmed and often ground up for the compost pile. When finished, just two canes are left. This is truly an ‘out with the old and in with the new’ approach.
Grape growers then nip off some of the buds on the remaining canes in order to concentrate the plant’s efforts into sprouting fewer shoots. Over the growing season as these new shoots grow and leaf out, some will be trained upward toward the sun and others will be thinned again. A careful ratio of leaves, shoots and grapes must be maintained to ensure exceptional and consistent fruit quality.
There are many ways to trellis grapevines but in Oregon’s Willamette Valley, most grapes are grown on a Vertical Shoot Position (VSP) set-up. The lowest wire, called the cordon or fruiting wire, runs vertically about 3 feet up from the ground. Above that can be as many as four or five crisscrossing catch wires, used to “catch” the shoots as they grow long and tall above the trunk of the vine. These catch wires keep the vines looking like a manicured vertical green hedge rather than sprawling out hither-dither across the rows.
Once the vineyard manager has chosen the two growing canes and nipped some of the still dormant buds, he or she gently attaches each to the fruiting wire, forming a T shape, with the trunk of the vine as the base. But if they have the time and patience, vines can be pruned based on each plant’s vigor. Those vines that tend to be more vigorous, as determined by last year’s growth, can benefit from a slightly modified pruning style. Pruners can use a technique to slow more vigorous plants by arching the canes up to the first catch wire, then back down to the fruiting wire. The vine needs to work a little harder to circulate sap to the end of each cane, thereby quelling the plant’s growth just a tad.
An interesting note about Oregon’s wine industry– the state has twice as many vineyards as wineries, which means there are double the grape growers as there are winemakers. According to the Oregon Wine Board 2014 Harvest report, there are 1027 vineyards with a total of 27,390 acres planted in vines. So now that you understand the basics of pruning, please come back and read more of our viticulture 101 process as we explain budbreak in a few weeks.