By Tami Schlies
We have watched a lot of videos over the years on pruning apple trees, both in the early, formative years, and on old trees that need to be seriously reformed. However, I think quite a few people likely have questions on how to prune other types of fruit, or even how to prune a seemingly finely formed tree to produce better. Here are a few pointers I have researched for my future own use I thought I would share with you.
Most apple trees develop fruit buds on stubby shoots called spurs. They are called spur bearers. A few varieties produce fruit buds on the tips of slender shoots that grew the previous summer and are called tip bearers. These will also have spurs, but in much smaller quantity, and they will tend to have a more lanky appearance than spur bearers. In order to optimize fruit production, each type of tree should be pruned in a different way.
If there is a shortage of spurs on a spur bearing tree, you can induce spur formation by cutting back the laterals grown the previous year to 4 or 5 buds in March or April. Each lateral will then grow 1 or 2 vegetative shoots from the upper buds, but the lower buds will usually produce flower buds at the end of the season to flower the following year. The next March or April cut back the vegetative shoots on the lateral to the topmost flower bud. If there is plenty of room, you can leave 3 or 4 wood buds on the vegetative shoot so the process repeats itself.
After several years of this type of pruning you may need to spur prune to keep 9 inches between spur networks on the framework, or else fruit size and quality will suffer. In March or April thin out spurs that overlap, grow on the underside, or are weak or shaded to 3 or 4 fruit buds.
Because tip bearers fruit on the ends of branches, many branches become too long and spindly to carry the fruit load. A good ratio for apple trees is for the central leader to be 3 times the diameter of the side branches. Tip bearing laterals must be pruned to strengthen the framework while still encouraging fruit production. Any shoots from the previous year that are less than 9 inches long can be left to bear fruit. Longer laterals should be pruned back to 4 or 5 buds. This will induce short shoots with fruit buds to grow that summer and flower the following year. Always prune the leaders of tip bearers to strengthen the framework and to encourage lateral growth that will bear fruit the following year.
Another issue in apple trees is biennial bearing. Some trees are genetically prone to it. Sometimes a late frost kills all the flower buds and induces a tree to begin biennial bearing. Other trees begin biennial bearing due to lack of nutrients or water one year, putting all energy into finishing that years fruit growth to the detriment of next year’s fruit buds. Once a tree starts this cycle it is difficult to break it, but there are pruning techniques that may help. In the early spring of the year a heavy crop is expected, rub off ½ to ¾ of the fruit buds. Leave only 1 or 2 buds per spur. This way enough energy is left to produce flower buds at the end of the season for the next year. Make sure to water and fertilize so the tree is not stressed.
Currants produce fruit on spurs that grow on 2 to 3 year old wood. Wood that is 4 years or older should be removed to make room for fruitful growth. A well formed bush has a clean stem coming out of the ground up to a height of about 10 inches. 8 to 12 branches should then come off of this evenly with an open center to allow light and air penetration.
The first year, encourage the growth of the stem and 4 to 6 branches. The second year, prune back any branches that are more than 8 inches long and allow 4 to 6 more side branches to arise from the stem, removing any shoots growing toward the center or down toward the ground. Reduce all other side shoots to 3 buds. In June of the third year pinch back all the side shoots to 5 leaves of the current season’s growth.
Since grapes are a fairly new crop here in the Far North, winter protection is likely a significant concern. If the vine is trained in a vertical hedgerow with the arms low enough to be below the average snow line, less mulching and winter care should be needed. When planting grapes, prune the cane back to 2 buds in early spring. That year allow a single straight trunk to grow to the desired height, then cut right through a bud at the lowest wire on your trellis. From the trunk allow 2 arms to grow, one in each direction along the wire. Tie them securely at periodic intervals. That October after freeze up, prune back the arms to 7 or 8 buds each.
The next year the grapes will produce shoots with flowers and fruit from buds on the 1-year-old wood of the arms. Train the new growth up the trellis, tying securely to support fruit. Allow only 1 fruit cluster per shoot. At the end of the year select new arms from shoots near the trunk that grew this year. Prune off the old arms and drop the newly selected arms into place along the bottom wire, tying securely. A secondary shoot should be pruned to 1 or 2 buds near the base of each new arm and left to supply new fruiting canes the next year. Prune these new arms back to 10 to 25 buds each.
Repeat the process in following years, always leaving 10 to 25 buds per arm. This may seem excessive, but about 90% of all new growth needs to be removed on grapes each year to optimize fruit production.
Kiwi vines are often trained very much like grapes. The arms, however, are generally only replaced every 2 or 3 years instead of every year. Kiwi can be tricky to prune because of excessive sap flow if they are pruned too late in the spring. Sources recommend mid February in the Pacific Northwest, so I would imagine mid to late March here in Alaska. On the other hand, summer pruning is highly recommended in many sources due to the vigorous growth of the vines. Definitely remove any unwanted lateral growth in summer before it twists around the shoots you wish to keep.
Like grapes, new fruiting wood develops on last year’s canes. In the summer, pinch any fruit carrying shoots back at 7 leaves beyond the last fruit. Pinch back barren laterals to 5 leaves as needed throughout the summer. Remove any sub-laterals that originate behind the pinched shoots. This type of summer pruning will encourage the formation of fruit spurs along the laterals.
In very early spring, laterals less than 3 years old should be cut to 2 buds beyond where the last fruit was born.
Any laterals 3 years old or more should be cut back to a dormant bud near the main cane to renew it as a fruiting lateral.