By: Tracey L. Kelley
Spring pruning is one of the most vital applications vineyard managers can control, so it’s always beneficial to cross-check your processes with an expert or two. Depending on the air temperatures in your region, you might be edging into budburst (also referred to as budbreak) right now, and believe most of your pruning is complete.
However, according to Fritz Westover, owner of Westover Vineyard Advising and Virtual Viticulture Academy in Texas, there are always reasons to examine the results of pruning not only at the start of the season but also throughout, to understand what worked and what should be remedied. Watch helpful instructional pruning videos from Fritz Westover.
“I do a lot of post-pruning site visits with growers, and it’s always informative to learn what you did wrong after you did it!” Westover joked. “The number one mistake I correct is the retention of small wood, followed by the retention of too many buds per vine. Both can result in an inefficient canopy, poor fruit quality and overall less balanced vines. The good news is that it’s easier to take buds off than to put them back on.”
Spur and Cane Pruning: Reasons for Each
“Ideally, the decision to spur or cane prune should be made before designing and planting a vineyard,” Westover said. “However, most varieties can adapt to either a cane- or spur-pruned system. Also, I’ve found both vertical shoot positions or high-fruiting wire training systems can adapt to spur or cane pruning.”
“A lot of our decisions regarding spur vs. cane pruning is based upon varietal,” Kim Myers told The Grapevine Magazine. Myers , co-owner, Laurel Gray Vineyards and Yadkin Valley Wine Company, along with her husband, Ben, co-stewards land in North Carolina that’s been in the family for 10 generations. Their 10.5-acre vineyard, Laurel Gray, features estate French vinifera vines such as Chardonnay, Viognier, Pinot Gris, Merlot, Cabernet Sauvignon, Cabernet Franc and Petit Verdot. Their winery, Yadkin Valley Wine Company, produces award-winning selections, including a signature Bourdeaux blend, Scarlet Mountain; Estate Barrel Fermented Chardonnay; and Estate Cabernet Sauvignon, Merlot and Viognier.
“Spur pruning is used for varieties that show high fruitfulness on basal buds. For example, Cabernet Sauvignon works very well on spur pruning—until it’s time to renew the cordons. When renewing, we cane prune in order to establish a new healthy cordon,” she said. “Viognier produced best when cane-pruned because this technique allows more light on to the cordon and into the canopy.”
“Generally, spur pruning, once established, is less labor-intensive. It’s easy to do and easy to teach, especially for vines that are trained on fences or trellises,” Myers added.
Westover provided further recommendations. “In general, sites that require in-row vine spacing wider than four feet are better adapted to a cordon/spur-pruning system to best utilize the space in the fruiting zone, as laying canes longer than 18-24 inches can result in poor shoot size uniformity in many varieties,” he said.
“Cane pruning, on the other hand, results in a vine that has a lower number of pruning wounds than a vine that is spur-pruned. Therefore, there might be less opportunity for certain fungal diseases that infect pruning wounds and cause grapevine trunk diseases,” he said. “Additionally, there’s less old wood on a cane-pruned vine and less potential area for disease spores to overwinter, such as phomopsis or other GTD-associated pathogens. Some varieties are also known to be more fruitful when cane-pruned, such as Nebbiolo or Malvasia Bianca.”
“Cane pruning requires a high level of expertise, is more expensive and takes more time,” Myers added. “You have to make very educated choices about each and every vine. However, cane pruning has many advantages: frost protection, even production and even spacing of growing shoots in the spring.”
Similar to what Myers does at Laurel Gray, Westover incorporates both methods for individual vines on some of his clients’ properties. “This isn’t typical, but can help increase the yield on vines that have high vigor but low yields due to small cluster size or shading of lower bud position of the spurs,” he said. “Careful consideration should be made as to where to use this practice, as the extra buds can cause crowding in the canopy, which can increase disease pressure in wet, humid climates.”
Another mitigating factor for following a pruning method is the rumbling advance of mechanized or “no-touch” vineyard operations. The University of California Agriculture and Natural Resources Department released data in 2019 from a 53-acre Merlot research vineyard in the San Joaquin Valley—where more than half of all California grapes are grown— that indicated mechanical pruning “reduced labor costs by 90%, resulted in increased grape yields and had no impact on the grape berry’s anthocyanin content.”
Kaan Kurtural, UC Cooperative Extension specialist in the UC Davis Department of Viticulture and Enology; and George Zhuang, UCCE viticulture advisor in Fresno County; conduct conference panels and webinars about the process, which they say is the future of pruning for operations of 150–300 acres.
So keep in mind as you strategize production growth and processes, “one of the greatest disadvantages to cane pruning in our future shift to mechanization is that it cannot be easily machine-pruned,” Westover said.
Questions of the Advisor
Since Westover consults for dozens of vineyards east of the Rocky Mountains through his onsite visits and victual academy, we asked him to provide answers to the top three questions he gets regarding pruning. They are:
1. When should I start pruning?
A: Depending on vineyard size, time and labor, if a grower in the Northern Hemisphere uses pre-pruning or partial pruning, I encourage them to start in January and move to final pruning at a time that allows them to complete it prior to budburst. So, for example, a small grower may be able to prune in a week and can start the process 10-to-14 days before the historical average budburst date in their area. Larger vineyards obviously need more time and may be pruning steady until budburst.
2. Do I need to protect pruning wounds from GTDs?
A: Fungal diseases associated with GTDs are primarily spread by splashing rain. Therefore, it’s important not to prune when it’s raining or when rain is predicted within the next few days—I advise my growers to wait until after the rain. In some cases, registered fungicides can be applied to protect pruning wounds from infection, such as Topsin M—check your state registry status. If pruning wounds have healed over, or if no rain is predicted, then protective sprays can be avoided. There are also products available now that can be painted over the top of larger pruning wounds to create a physical boundary against pruning wounds, such as VitiSeal.
3. What if I don’t finish before budburst?
A: Ideally, all final pruning will be completed a week or so before budburst. When shoots begin to grow, they first emerge on the most distal part of a cane, which is referred to as “apical dominance” of shoots across a cane. Some growers intentionally hold off final pruning until the onset of budburst on distal bud positions, as this can delay the budburst of the lower buds retained as spurs near the cordon. This small delay in budburst can result in the avoidance of a late spring freeze by 7-to-14 days, depending on site and variety. However, if a grower doesn’t complete final pruning before the shoots on the distal nodes reach greater than two inches in length, the lower bud positions can lose fruitfulness. The bottom line: pruning needs to be completed by bud swell—and not later.
Education, Sterilization, and Clean-Up Ensures Successful Results
Many vineyard managers hire crews with pruning experience, while some do a crash course each season with trusted volunteers. In either scenario, Westover said, you need to ensure people do what your vines require.
“Cut-and-paste pruning strategies won’t address the needs of each block. A pruning crew is only as good as its instructor, and it’s often necessary to have a lot of supervision the first few days of pruning—and again any time the pruning strategy changes between vineyard blocks,” he said. “Educate your crew and stick with them until the end. I share videos with my clients from my website, and on a rainy day, the crew watches those. Repetition of key pruning concepts is a great way to empower your crew to make decisions on their own and quickly.”
One example he provides is that vigorous vines with large cane diameters can retain spurs with two-count buds, whereas smaller vines or vines with some small canes may need to have several spur positions pruned back to a one-count bud. “The motto I use in my academy is ‘no wimpy wood’—which seems to resonate with growers and results in less wimpy shoots that produce inferior fruit,” Westover of Virtual Viticulture Academy told The Grapevine Magazine.
“Weather can also cause a shift in a standard pruning protocol. For instance, in a year with high primary bud death due to freeze conditions, a grower needs to first assess the percentage of bud death in the vineyard, and then adjust the final number of count buds per vine to compensate,” he said. “This isn’t easy to do, but it can certainly help keep a vineyard in business through a tough season if done properly—and some live buds remain!”
Myers’ pruning team includes two people on staff for a 40–plus workweek who are in the vineyard daily. One of her primary takeaway tips is proper sterilization. “Clean pruning tools at the end of each row, and especially when changing varietals.”
Westover agreed. “This is an area of research that we have little information on at this time, but sterilizing shears after each row and—at a minimum—between blocks is a good practice. Solutions of 10% bleach or 70% isopropyl alcohol are inexpensive options to spray on shears,” he said.
So is the work done once buds break? Not necessarily. “Stay proactive on your vineyard management programs from pruning until frost to avoid uncontrollable problems,” said Myers of Laurel Gray Vineyards. “Watch for split vines that may have happened due to extreme cold weather when the sap was rising. Remove all cut wood from the vineyard floor and spray while still dormant with lime sulfur to kill any disease spores that overwintered in mummified fruit, dead wood or old leaves.”
Also remember that not removing enough canes “will cause over-production with a too-dense canopy, under-ripe fruit and conditions for disease,” she said. “These conditions require more labor through the growing season because the vineyard manager is constantly trying to combat these issues through summer hedging, spraying and leaf removal.”