Dormant pruning

Dormant pruning of kiwivines is best done in late December to late January in the Pacific Northwest. Late-pruned vines may have excessive sap flow, which may weaken vines.

In kiwifruit, flowers are produced on current-season shoots that grow from buds developed on 1-year-old canes (last year's growth). Shoots that grow from older wood seldom produce fruit in their first season. Shoots from buds that were heavily shaded during the preceding season are less productive than those from buds that were exposed to the sun. That's why it's important to prune well so that the canopy is open and well exposed to light. Research at Oregon State University has shown that hardy kiwifruit start initiating flowers for next year's crop in July and that shading reduces the number of flowers formed.

Our research has shown that in A. arguta, all 1-year-old canes and spurs are equally productive per foot of length and produce a similar fruit size, regardless of

Kiwifruit Male Pruning
Figure 5.—Mature portion of a kiwifruit cordon in production. Leaves are not drawn to simplify the figure. Fruit are produced on shoots growing from last year's growth. Winter pruning cuts are shown by ^.

where they originated (cordon, 2-, or 3-year-old wood). That's why it's easy to prune a kiwivine too lightly, leaving too many fruiting buds. The most productive part of long 1-year-old canes is from nodes 6 to 40. The buds at the base of canes usually produce only a vegetative shoot (no flowers). The fruitful buds produce shoots that bear flowers from nodes 6 to 12.

When mature, male and female plants should be pruned differently.

Female vines. When pruning a mature vine, remove about 70 percent of the wood that grew last season. Most of the wood removed is older wood that already has fruited. New fruiting canes usually will have developed at the base of last year's canes. Figure 5 shows a typical fruiting cane that developed from the permanent cordon.

Replacement fruiting canes that originate from the cordon may be left to replace older wood in the future. Fruiting canes should be separated by about 8 to 12 inches on the cordon. Head back replacement fruiting canes to force growth next season, and tie them to the wires for support. Do not tie canes too tightly or they'll girdle during the growing season.

Spurs (shorter fruiting branches with short internodes) often originate from the older wood. Do not remove them unless necessary, as they also are fruitful (Figure 5).

Remove most of the older wood back nearly to the cordon. When necessary, you can leave some 2-year-old wood with its 1-year-old wood attached for fruiting wood if 18 to 48 inches of new off the vine. The area of the cane that bore fruit last year (normally nodes 6 to 12 in hardy kiwifruit) will not have buds present and thus will not produce any shoots. Expect from 25 to 57 percent bud break (typically about 50 percent).

Take care that 1-, 2-, and sometimes 3-year-old fruiting canes are distributed evenly on the

Kiwfruit Cane
Figure 6.—Dormant portion of a mature kiwifruit vine cordon. Winter pruning cuts are shown by ^. Shoots labeled with an "F" fruited last season.

growth is present beyond where fruit was formed last season (Figure 6). Head back these fruiting laterals to 2 to 4 buds in fuzzy kiwifruit and to 8 to 12 buds in hardy kiwifruit beyond where fruit was formed last year. Often you can see where the fruit was borne last year because the old fruit stems (pedicels) do not fall trellis to avoid overcrowding in any area of the canopy.

Remove twisted and tangled growth, shoots that cross from one side of the vine to the other, and wind- or cold-damaged shoots. Mature vines, spaced at 15 feet in the row, should have 30 to 45 fruiting canes per vine (spaced at 8 to 12 inches on both sides).

Male vines. The goal when pruning male vines is to produce as many flowers as possible for pollination, while keeping the vine manageable. It is best to prune male vines only lightly in the dormant season—just enough to remove tangled shoots and keep vines manageable. After flowering (late June), prune male vines, using the same principles as discussed for the female vines.

In hardy kiwifruit we have found that the cordons of female and male vines need to be replaced every 3 to 4 years. To replace the cordon, lay a vigorous vegetative shoot down along the center training wire in each direction. Do this the year before you plan to remove the old cordon. The following season, lateral shoots will be formed along the new cordon; space these as discussed in "Establishing Your Kiwifruit Vineyard." Once a good replacement cordon and fruiting canes are established, cut off the old, unproductive one.

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