The Proof is in the Pruning – Post Bud Break Vine Assessment

Bud Break

Bud break is occurring at similar times on California's Central Coast and Texas in 2015.

Bud break and young shoot growth is occurring rapidly across the states and warm temperatures are hastening the work load for vineyard management crews. Application of the first protective sprays is the first thing on the mind of most growers at this time. It is easy to get lost in the details of the next task when shoots are growing rapidly, but let’s not miss the opportunity to take a critical look back at the pruning work that has occupied the past few months. Pruning is the most important vineyard task. If done properly, it will simplify all vineyard tasks to follow in the season. A critical assessment of your pruning job can best be determined after bud break. Hence, the proof in the success of your pruning strategy is by now (or soon to be) evident. Here are a few things to look for:

Bud Count Vs. Shoot Number

Example of spurs pruned back to 2 count buds (in green circle) and non-count bud (in red circle).

Example of spurs pruned to 2 count buds (green) and 1 non-count bud (red).

Let’s be realistic, no experienced pruner will take the time to count buds on each final pruned vine. When training a new pruner, I often suggest they count buds on the first 20 vines pruned to calibrate their eyes. After the eye is trained an occasional follow up count on a vine will help test their proficiency. Within a week of bud break we can truly assess if our bud number retained resulted in an equal number of shoots. But for the most part, when leaving two count buds on a spur, we expect see two fruitful shoots developing from that spur. The disagreement from bud count to shoot number often occurs when the pruner does not properly identify count vs. non-count buds. Distinguishing count buds can be a challenge for new growers, which is why it can be very helpful to look at what sprouts out of the vine this time of year. Fruitfulness of buds is in part determined by genetics, but other factors such as freeze damage, vine nutrition, virus, and poor weather conditions during bud development in the previous season can affect the survival and fruitfulness of a primary bud. If follow up counts are made on a few vines, after a few years of observation one can adjust bud counts to better target the resulting number of fruitful shoots for each variety in the vineyard.

Shoot Distribution Uniformity

Example of even distribution of 2 bud spurs on a vertical shoot positioned vine.

Example of even distribution of 1 and 2 bud spurs on a vertical shoot positioned vine.

Part of the art of dormant pruning is not only to eyeball the proper number of count buds, but also to retain them in such a way that promotes uniform distribution of shoots along a fruiting wire. The two most common areas of shoot “congestion” occur near the head of a vine where non-count buds commonly push, and at the end of cordons/canes where overlap can occur from a neighboring vine’s cordon/cane. Vigor of shoots derived from those two areas can also be greater, which adds to the congestion (and the shading and disease pressure in the canopy). Shoot thinning early in the season is one way to overcome the crowding in these areas. One tip for spur pruning that I often use with new growers is to allow a hand width between each spur position, and also between the ends of neighboring cordons. In the end, a little shoot thinning can always help to improve shoot distribution in the canopy. I recommend growers strive to reduce the workload at thinning time by pruning for uniform distribution.

Size Matters

Example of cutting out small diameter wood, in this case lateral wood on developing cordons.

All small "wimpy" diameter wood should be removed when pruning - in this case lateral wood on developing cordons.

After more than a decade working as an extension educator and consultant, it is my observation that the most common mistake of the dormant grapevine pruner is to retain small diameter wood. The ideal range of acceptable, fruitful wood for spurs/canes is from 5/16 to 1/2 inch diameter, or about pencil to sharpie size wood. Wood smaller than this range is often weak, producing smaller shoots and weak spur positions in succeeding years. It is also a poor choice for developing trunks or cordons on young vines (in which case the larger end of the range is preferred). There can also be some disadvantages for wood larger than this range. Large caliper wood, often referred to as “bull wood” is does not push buds as reliably and can often have long internodes, leading to problems with shoot distribution uniformity. Likewise, there can be many gaps in the canopy from non-push buds if bull wood is used for cane pruning or cordon development. My two favorite mantras for dormant grapevine pruning are “no wimpy wood” and “when in doubt, cut it out.” I also have been known to say, “no junk on the trunk” but we can save that for a future post on vine suckering.

Renewal Experience

Dominance of apical buds shown on cane pruned Cabernet Sauvignon. Note the distal bud is most advanced on cane and on spurs near trunk head.

Dominance of apical buds shown on cane pruned Cabernet Sauvignon. Note the distal bud is most advanced on the cane and also on spurs near trunk head.

Example of stepwise cordon development on a 2nd year vine pruned with 5-7 nodes on each developing cordon.

Stepwise cordon development on a 2nd year vine pruned with 5-7 nodes on each developing cordon. Trunk formed in 1st year.

Example of the cordon "bridging" technique for filling in cordon gaps in declining a vineyard.

Example of the cordon "bridging" technique for filling in cordon gaps in a declining vineyard block.

In general, there are two reasons to lay down canes to renew your cordons; 1) you are training a young vine and you do not yet have a cordon and 2) you are experiencing cordon dieback due to fungal diseases in the wood, poor vine training, or both. Grapevines are well known to express apical dominance in bud positions most distal from the base of one-year-old wood.

 

 

When developing cordons in either the renewal or the initial development stage it is best to do so in a stepwise fashion, allowing no more than about 5-7 buds or 18” of cane laid down per season. Leaving shorter canes promotes more even bud break, hence less blank spots on the fruiting wire. When cane pruning, this rule is often disregarded because the cane is removed each year.

Cordon renewal can be a daunting task in large vineyard blocks, requiring trained crews and multiple years for completion. This is why we often see short cut fixes to blank spaces on cordons, such as the ugly, but often used bridging approach. These practices are more often used to simply sustain production when the block is destined for a replant in the coming years. The first few weeks after bud break is a good time to assess gaps in the canopy and their impact on yields.

A Tie for Every Occasion

Example of a stretchable tubular tie (on left) replacing a temporary vine training tie (green tape) on the right.

Example of a stretchable tubular tie (left) replacing a temporary vine training tape (right).

Regardless of the training system or age of the vine, some form of tying material is needed to keep the vine on the trellis system. The main reason I bring this up here is because many new growers forget to upgrade tying materials after the first few years of vine training. There are plenty of options for tying materials on young and mature vines. It is easier to start with what not to use. Anything that is not flexible has the potential to girdle vines and thus should be avoided. The leading culprits for vine girdle include, zip ties, hard plastic ag-lock ties, and wire. Do not let these items in the vineyard unless used to tie training stakes. No one will go back and “loosen” them later as the vine grows, so it is best to avoid them in the first place. I prefer using temporary material when training vines, and upgrading to a stretchable tie once permanent structures are selected for tying down. For example, thin green tape stapled with a tapner gun works well for training green growing shoots. A grower can then switch to a stretchable tubular tie or even twine for the next few years of vine development. Keep in mind that even flexible ties can girdle vines if tied on too tightly. If you aim to have a crop in years 2 or 3, then plan to have stronger support than is offered by a one-year tie.

Comments

  1. Tim Martinson says:

    Nice blog, Fritz!

  2. Allen Robinson says:

    This is great Fritz. I will have to come back and re read it but WOW. Nice job

    Allen

  3. Russell Moss says:

    This is sweet Fritz 🙂 I like the “count” and “non-count” graphic.

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