Grape Days: Pruning trials under spotlight
Two studies in Marlborough reveal changing the way vines are pruned and treated for trunk disease could save money without impacting quality.
According to the 2024 Marlborough Vineyard Monitoring Report, one third of surveyed grape growers had either started long spur pruning of Sauvignon Blanc vines or planned on trialling it over winter 2024, citing cost savings as motivation.
While unfamiliarity might have held growers back in the past, current profitability might see a considerable swing to spur pruning.
Once the cordon and spur sites have been fully established the time to prune a vine can be reduced by half, says viticulture consultant Mark Allen, who has been involved with researching spur pruning, and instatlling the system in new and establishing blocks, for 24 years.
Mark, who was recently named a 2025 New Zealand Winegrowers Fellow for his dedication to translating research into the field, says long spur pruning is very similar to the new approach taken in canopy layout for cherry and apple trees.
That means Hawke's Bay and Gisborne grape growers could be more open to the shift than Marlborough growers, as they have more exposure to the changes over the fence.
Over the years he has redesigned the system, "to make it even better", for example moving from 100mm spur spacings, which led to shading, to a 180-200mm gap between spurs, and double the number of nodes, to get the same number of buds per metre without crowding.
Spur pruning is the preferred canopy for mechanisation, with potential for further cost cutting and robotic assistance, Mark says.
It is just as easy to get a high crop yield with long spur pruning as it is four canes, he adds.
“Spur pruning at 180-200mm will enhance light interception onto nodes one and two and increase fruitfulness.”
Long spur pruning can be set up with new vines, either as unilateral or bilateral cordon, or retrofitted from four or three cane systems.
“It is easy to manipulate the numbers with spur pruning and it’s quicker to count buds on spur pruning as they are upright.”
If growers want the option to go back to four cane pruning, then it’s best to set up as bilateral cordons with four vines per bay at 1.8m, Mark says.
“Some new developments in Marlborough are looking at doing this, and others unilateral cordons.”
He sees particular benefits in retrofitting old vineyards with trunk disease. This is useful where owners are not ready to replace vines altogether, but crop levels are low. The gaps can be filled by extending cordons from neighbouring vines that are grown longer on the wire and fill in the gaps.
In terms of keeping trunk disease out of a vineyard, Mark said growers have made far too many big cuts into grapevines, when whole arms or heads are removed. This rolls out the welcome mat for trunk disease. The spur prune cuts are only finger width, with far less surface area.
He says the whole vineyard (spur-pruned vines, posts and wire) should last to 45 years. Mechanical shaking spur pruned vines still has a positive effect on yield reduction and botrytis reduction, even though the bunches are a bit more ridged.
Spur pruning expertise is more readily available now, Mark says.
“Several contractors have dedicated spur pruning teams.”
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