The art of pruning back a vine or a tree is all about finding the right balance for improving fruit quality and quantity.
The first thing to understand is that only buds from last year will produce fruit this year. So imagine a grapevine that has one cane from last year, and this cane has 12 buds. Each of those buds will produce a new cane this year (with two or three clusters of grapes). But the next year (without pruning) the vine may have 144 buds (12 canes with say 12 buds each) and following year (without pruning) might have 1728 buds (144 canes with 12 buds each).
The image is a vine out of control, trying to sustain all that growth with essentially the same root system. What ends up happening is that the canes get spindly and the grapes clusters (if there at all) are smaller and smaller. Thus the wild grapevine near a creek we’ve all seen.
For many, the beauty of vineyards is how the vines all line up perfectly with such spectacular precision and elegance. Screw those people! All this “perfection” takes time and effort on our part, both in the choice/implementation of the trellising system and the continual training of the vine.
With 85 acres of vineyards (planted in different “eras” of vine trellising technology), we essentially use three different methods of pruning; cane pruning, cordon (spur) pruning, and vertical cordon pruning.
Cane Pruning—This is by far the preferred system of pruning in our vineyards (70 of the 85 acres). Although cane pruning is the most difficult, time-consuming and skill-oriented, we find it balances the needs of older vines. The basis of cane pruning is to choose two canes from last year’s growth to tie down on the wire for this year’s crop. Each cane (one running each direction on the wire from the head (trunk)) is trimmed to have 6 or 7 buds on it, and never having a girth smaller than a pencil. That in itself seems very simple.
The skill in cane pruning is the preparation for next year’s canes. In other words, we need to be thinking about where the vine’s replacement canes will be coming from in 12 months from now. The art is leaving a couple spurs in the head of the vine (the center) to grow the canes for next year. If we don’t leave enough spurs in the right area of the head, we run the risk of not having suitable replacement canes next year (and no crop). If we leave too many spurs, the head becomes too dense with growth causing airflow and potentially mold/mildew issues for the vine.
Thus having skilled people doing the pruning is paramount for our success. Ideally, our crew is small (4-5 people) who do all the pruning, giving us consistency throughout the vineyard and success for next year’s harvest.
Cordon Pruning—Cordon pruning or spur pruning is a different concept. The idea behind a vertical cordon is that over the years we keep the same wood growing on the wire instead of choosing a new cane every year. But remember that only last year’s buds produce fruit.
So the first year we would have a cane on the wire. But instead of cutting it off after harvest and choosing a new cane, we would retain that older cane (or cordon now) on the wire and trim all the new canes (from this year’s growth) to just the two closest buds to the cordon.
Since each position on the cordon will produce two new canes (from each two-bud spur), we need to cut out every other spur position to balance out the growth. Ultimately, there will be 6 to 10 new canes growing on each side of the cordon producing fruit.
The benefit of this system is that it’s fast and easy to prune and doesn’t take much training for new personnel. There’s little need to make difficult decisions extrapolating a year into the future (like with cane-pruning), and portions can be done with a tractor if automation is where a winery wants to go.
The challenge for cordon pruning is spreading the grape clusters throughout the fruiting area (in other words, not having the clusters touch each other). Generally, fruit quality is improved when it hangs freely open on all sides.
And for us at Madroña, we tend to find yields on older vines drop over time with cordon pruning. (And we have mostly older vines now.)
Vertical Cordon Pruning—So a vertical cordon is not unlike the horizontal cordon on wire except that is completely vertical (thus the name!). Imagine a vine that grows up a post more like a tree, having a “trunk” with the 2-bud spurs placed along it. The fruiting zone is no longer in a defined narrow area (which tends to give more uniformity), but is instead vertically varied from two to five feet or so.
The benefits of a vertical cordon are not unlike the cordon pruning above. It’s easy and fast to prune, not needing much training or skill to do. And there is the other benefit that the grape clusters are spread out generally hanging unencumbered by other clusters.
The challenge with a vertical cordon is the potential for the grapes to ripen at slightly different rates. It’s amazing how temperatures fluctuate in such a small 3-foot area with the soil warming during the day (from the sun) and cooling doing the night. These differences go counter to the thought of having a uniform ripeness.
However for a variety like Zinfandel that showcases unique characters at different ripenesses, a vertical cordon can be a good system to choose.
Truly, there is no perfect pruning system. In all honesty we use hybrids of all these systems including kicker canes (an extra cane), cane-pruned quadrilateral systems (two fruiting wires with four canes), and layered canes at different fruiting wire heights. Having multiple systems provides some insurance that we’ll get everything pruned before the springtime budding while emphasizing the quality of the fruit.
In the end, though, nothing is ever permanent. The great thing about choosing how you want to prune is that ultimately the vines are very forgiving. If you decide that one style of pruning doesn’t achieve what you need, you can eventually change things around.
So the next time you drive by and see people pruning, give a nod celebrating the planning and skill incorporated in the art of pruning!
Read The Art of Pruning – Part 1