If you grow fruit plants, you know that you need to prune them occasionally. Pruning increases your chances of having healthy plants that bear tasty, easy-to-reach fruits year after year. A well-pruned plant pumps more energy (which translates into flavor) into the remaining fruits. Removal of some fruits one year can prepare the plant for a bountiful harvest the next year. Pruning also keeps fruit-bearing stems from growing beyond reach or becoming a tangled mess that's prone to disease.
Fruit plants vary in their pruning needs. Three common fruit plants—raspberry, grape, and apple—represent the spectrum of bearing and growth habits and serve as good examples of how to prune fruits. Late winter or early spring is the time to prune these plants.
How to prune raspberries
Raspberries, which are suckering shrubs, are among the easiest of all fruit plants to prune. Their roots are perennial; individual canes are biennial.
Canes of summer bearing varieties grow stems and leaves their first year, fruit in midsummer the next year, then die. Everbearing (also called fallbearing) varieties bear their first fruits near tips of new canes in late summer and fall, then reward you again the following midsummer as they finish fruiting lower down on those same canes, after which those canes die. ("Two-crop" is a more accurate name than "everbearing" for these raspberries because you'll harvest two crops, the first in midsummer on one-year-old canes, and the second in late summer and fall on new canes.)
All raspberries give you fruit every year, of course, because new canes grow from ground level every year.
Prune raspberries in three easy steps. For the first step, cut to the ground any canes that are two year sold. They are dead or dying anyway.
The second step is to remove excess one-year-old canes. Cut to the ground any canes that have wandered beyond a 1-foot-wide row. Also remove enough canes within the row so that none are closer than about 6 inches apart. Save the healthiest young canes.
Finally, shorten the remaining canes to prevent them from flopping around. Five feet tall is about right, although it depends on how self-supporting the variety is and whether or not you grow them on a trellis. For this last step, cut canes of everbearers back to below where they stopped fruiting the previous fall, as indicated by remains of old fruit stalks. Or (even easier) sacrifice the summer crop of everbearers and plan for only the later crop by cutting the whole plant to the ground each winter.
How to prune grapes
You wouldn't know it with just a casual glance at the plant, but grapes bear similarly to raspberries. They bearon one-year-old canes, except that these canes rise up in the plant rather than from ground level. You can easily distinguish a one-year-old cane from older wood because the bark on a cane is smooth and tan, where as bark on older wood is dark and peeling.
For home gardeners, the best way to prune grapes is what's known as the four-arm Kniff in system. Such a vine consists of a trunk from which grow four horizontal, fruiting canes. Two canes grow in opposite directions along each of two horizontal wires at 3 and 5 feet above ground level.
To prune annually using the four-arm Kniff in system, start by marking four canes with a ribbon so that you do not accidentally cut them off. The best—that is, the most fruitful—one-year-old canes are those that are moderately vigorous and about pencil thick, with 6 to 12 inches of space from bud to bud. Choose two canes that are growing in either direction along the top and the bottom wires and originating near or right from the trunk.
Next, select four "renewal spurs," two near each wire. Renewal spurs offer buds that are likely to grow into well-placed canes for the following year, so the wood can be any age as long as it has two or three plump buds near its base and originates at or near the trunk. Cut back each renewal spur to two buds. When this year's one-year-old canes (the ones you marked with a ribbon) become two-year old canes and no longer bear fruit, these renewal spurs will grow and bear fruit.
The third step is to cut off all growth except the four canes, the four renewal spurs, and the trunk.
Finally, shorten the fruiting canes that you saved to about ten buds each—more if last year's growth was vigorous, less if it was weak. Do not count the cluster of buds near the base of a cane.
In very cold climates, train a vine to multiple trunks or to a low trunk that grows from ground level at an angle, so you can mulch canes for winter protection. To do this, tie the canes along a low wire just before growth begins. As the growing season progresses, tie fruiting shoots growing from these canes to an upper wire, to bathe in sunlight and air. Old trunks are most susceptible to winter damage, so periodically replace an old trunk with a young one. You won't have to sacrifice even one season's harvest if you train your vine to multiple trunks.Click here to view PDF on how to prune grape vines.
How to prune apples
In contrast to raspberry bushes and grape vines, established apple trees require only a moderate amount of pruning and some finesse. Apples bear fruit on spurs, which are stubby branches that grow only about ½ inch per year on wood that's more than two years old.
Left to their own devices, apple trees try to grow too much, especially higher in the tree, so a neglected tree becomes top-heavy and shades itself too much. Prevent this situation by completely cutting away, right to their bases, any watersprouts (overly vigorous upright stems), which are most prevalent high in the tree.
Lower in a tree, you often find weak growth. Cut away short twigs hanging from the undersides of branches and shorten drooping stems back to horizontal growth.
After about ten years, fruiting spurs become overcrowded and decrepit, so give them room and invigorate them by removing some and shortening others. When a whole limb of fruiting spurs declines with age, cut it back to make room for a younger replacement.
A few apple varieties—‘Cortland' and ‘Idared', for example—do not bear fruits on spurs, but at the ends of willowy stems about 6 inches long. Avoid shortening too many stems on mature trees of these varieties, or you'll cut off too much of your potential crop. Leave stems of moderate length, and encourage compactness and branching by shortening very long stems instead.