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May 2016 WINES&VINES 29 a fruiting wire (see photo at right). 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 cor- dons/canes, where overlap can occur from a neighboring vine's cordon or cane. Vigor of shoots derived from those two areas can also be greater, which adds to the congestion (and shading and disease pressure in the canopy). Shoot thinning early in the season is one way to overcome crowding in these areas. One tip for spur pruning that I often implement with new growers is to allow a hand's width between each spur position and also between the ends of neighboring cordons. A little fol- low-up may still be needed to shoot thin in the spring, but it will likely be faster and more economical. I recommend growers strive to reduce the workload at thinning time by prun- ing for uniform distribution and following up after bud break to see if the bud count strategy needs adjusting in future seasons. Size matters After more than a decade working as an exten- sion educator and consultant, it is my observa- tion that the most common mistake by dormant grapevine pruners is retaining small-diameter wood (see example on page 28). The ideal range of acceptable, fruitful wood for spurs and canes is between 5/16 and a half inch in diameter, or about pencil- to Sharpie-sized wood. Wood smaller than this range is often weak and produces 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-caliber wood, often referred to as "bull wood," 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 grape- vine 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 article about vine suckering. The effects of leaving weak, small-diameter wood can best be observed when shoots are 12-24 inches long. At that time, differences in shoot size can be visually correlated to wood size retained at dormant pruning. Renewal experience 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. 2) You are experiencing cordon dieback due to fungal diseases in the wood and/or poor vine training. Grapevines are well known to express apical dominance in bud posi- tions most distal from the base of one-year- old wood (see bottom photo on page 30). When developing cordons in either the renewal or the initial development stage, it is best to do so in a stepwise fashion and allow no more than Put Your Money Precision Frost Protection, Target Those Frost Pockets! READ MORE ABOUT IT AT www.shurfarms.com Where Your Frost Is! SHuR FARMS Frost Protection Colton, CA (909) 825-2035 info@shurfarms.com One- and two-bud spurs are evenly distributed on a vine with vertical shoot positioning (VSP) trellising. GRAPEGROWING