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Figure 2 Figure 3 The fundamental "fruiting unit" in sweet cherries involves three years of growth, each section having distinct leaf populations and fruiting potential. Two-year-old growth Spur fruiting sites (fruit density increases terminally) 7 to 9 leaves per node (fruiting spurs) Previous year growth Nonspur basal fruiting sites (no vegetative buds) 6 to 8 leaves per node (nonfruiting spurs) Large (9-row and larger), well-exposed fruit borne primarily on basal (nonspur) fruiting sites. The tree is Rainier on Gisela 5 rootstock grown near Benton Harbor, Michigan. Current growth Single leaves per node This idea of preemptive pruning is illustrated for the fundamental sweet cherry fruiting unit in the "Pruned" section of Table 1. By making a dormant pruning cut to remove the terminal 15 to 20 percent of the previous season's shoot, about 30 to 35 percent of the nodes will be removed due to the spur density, and this will translate into about 45 percent of the future number of fruiting sites on that section of wood as those nodes mature into fruiting spurs. This preemptive pruning cut not only removes future crop load, but also stimulates new shoots to form (in the illustration in Table 1, pruning promotes the conversion of two remaining nonfruiting spurs into new shoots), thereby altering the spur leaf and shoot leaf populations. The result is fewer fruit, fewer (moderately sized) spur leaves, and more large new shoot leaves. Thus, the LA:F ratio that fell dramatically (as the unpruned branch aged) is maintained by preemptive pruning at about twice the value of a non-pruned shoot, resulting in better fruit size. The fruit population is shifted toward higher proportions of nonspur fruit (the basal fruits that are generally the largest in the tree canopy, see Figure 3), and the leaf population is shifted towards higher proportions of large new shoot leaves. Naturally, other types of pruning decisions, which further impact LA:F ratios, are also generally necessary, and will be discussed below, but the concept of preemptive pruning for crop thinning, and shifting cherry tree growth to develop the most favorable fruit and leaf populations, remains a foundational orchard management concept for attaining large fruit size. Other cuts Other pruning decisions that impact fruit size and quality include dormant or summer thinning cuts to remove: 1) pendant shoots, which tend to produce poor quality fruit and create interior shade in the canopy; 2) upright (especially water-sprout-type) shoots, which also create interior canopy shading; and 3) closely overlapping fruiting shoots, to further minimize shade. Light-exposed fruit have been proven to be firmer, sweeter, and larger than shaded fruit. Timing of pruning can have indirect effects on fruiting. Large structural cuts are best made in late summer, when they won't stimulate vigorous regrowth that could draw resources away from developing fruit, as may occur when such cuts are made in late winter or early spring. Table 1 A conceptual accounting of the fundamental leaf and fruit populations on sweet cherry branches as they age and respond to annual dormant pruning to remove 15% of the previous year's shoot length (which removes 30% of the nodes that would become spurs and 45% of the future flower buds). LA:F = leaf area-to-fruit ratio. Not pruned Year 1 2 3 4 5 Fruit populations Number of units Nonspur 0 10 10 10 10 Spur 0 0 75 150 225 Total 0 10 85 160 235 Leaf populations (fruit or leaves) Shoot (spur equivalents) 10 10 10 10 10 (20) (20) (20) (20) (20) Spur 0 60 120 180 240 Total 20 80 140 200 260 LA:F - 8.0 1.7 1.2 1.1 Pruned 2 3 4 5 10 20 40 80 0 41 123 287 10 61 163 367 20 40 80 160 (40) (80) (160) (320) 30 90 210 450 70 170 370 770 7.0 2.8 2.3 2.1 In areas where bacterial canker is an issue, all pruning should be done when there are forecast windows of dry weather to reduce the potential for canker infection. The larger the pruning cut, the longer the dry weather window to allow the cut to heal. Thus, the calendar sequence of pruning might involve: 1) late-summer pruning if large structural cuts are needed; 2) dormant pruning of young wood for fine structure, preemptive cuts to maintain balanced cropping by eliminating future dense clusters, and the stimulation of new leaf area close to the fruit-bearing wood; and 3) late-spring or postharvest pruning to maintain light channels throughout the canopy and remove extraneous new shoot growth that would shade developing flower buds and spurs. • Our Reputation Is Everything To Us! ® Performance You Can Count On! 290 Series: 5', 6', 7' WIDTHS 3008, SWING HITCH 3210: 10.5' WIDTH 3209: 9' WIDTH 3210, SEMI MOUNT 3008: 8' WIDTH 290 Series Burrows Has Been a Full ServiceBush Hog Dealer for 45-plus Years! When you buy BUSH HOG, you get great performance NOW AND FOR YEARS TO COME. 5 Year Limited Gearbox Warranty www.goodfruit.com GOOD FRUIT GROWER July 2013 15