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What to know about pruning your small fruit plantings

With the current, albeit temporary, heat wave and rainy weather that have engulf us, I find that gardeners are awaking from their winter hibernation and are beginning to take an interest in their small fruit plantings. Soon will be the time that those plantings will need to be pruned so they can perform at their best. There’s some things to keep in mind when pruning your small fruit plantings.

As a rule, berry plants like raspberries, blackberries, blueberries and currants produce best on young wood. Removing old and weak growth will improve your crop. Berry pruning is not difficult and I find that gardeners are more likely to do a good job of it if they understand why seasonal pruning is important.

Cutting away less productive portions of a plant allows more water and nutrients to enter remaining strong buds, stems and branches. The whole reason to plant berries is to enjoy their fruit, so why not take the time to manage your plants for the best crop possible?

Pruning berries means three things: removing, shortening and thinning. Weak, slender wood bears few fruit. Long unbranched stems grow out of reach and produce few fruiting side shoots. Crowded stems are very poor producers.

For red raspberries, keep canes or stems 8 inches apart and narrow each row to 12 or 18 inches wide so you will have about two and one-half canes per foot of row. Remove all suckers that grow out of the soil and around the base of the plants. Shorten remaining canes that grow from the crown of the original plant by cutting 20 to 25 percent from the top.

Fall bearing red raspberries (such as Heritage), which produce very late season, berries on wood grown the same season and are easy to maintain. Cut all canes to the ground in the fall after harvesting or in March before new growth begins. Later in the spring, once growth begins, prune canes to the same spacing as outline above for regular season raspberries and remove suckers. Do not shorten any stems during the spring or summer growing season.

For black raspberries, shorten the lateral or side branches to 8 inches to encourage more flowering and fruiting stems. Don’t be afraid to take out some of the stronger stems to prevent overcrowding, as canes will fill out in the spring. Pinch new stem growth when it reaches 18 inches by removing the tip or the stem. This will encourage lateral shoots that will flower well.

For purple raspberries, shorten the lateral canes to 12 inches and keep crowding to a minimum. Pinch new stems when they reach 24 inches long to encourage side shoots.

For blackberries, shorten laterals to about 12 to 18 inches to make plants more compact. Cut out all laterals close to the ground since shade from upper stems will reduce their flowers. Fruit from pruned laterals will be far larger than fruit from unpruned weak wood. Thin canes to 10 inches apart and pinch new canes when they reach 30 inches long to stimulate fruiting side shoots.

Here’s what to know what blueberries, one of my favorites. This recommendation is for plants three years and older. First remove the small bushy growth near the base of the plants. Each year remove one or two of the fruit bearing branches with the overall goal of maintaining plant with wood no older than 5 years.

For currants that are two-year-old plants, leave six to eight of the strongest shoots. On three-year-old plants, remove weakest wood. On plants 4 years and older, maintain a cutting schedule to have three shoots each of 1, 2 and 3 year old wood. There should be no wood in your plant over 3 years old.

For grapes, it is important to remember that they grow from shoots or buds on canes or branches grown the previous year. Prune every year in later part of winter or early spring while plants are still dormant. The best fruits are borne on pencil-sized canes. Most methods recommend keeping plants pruned to four lateral canes with 10 to 15 buds on each. Train two sets of parallel canes on supporting wire fence and tie loosely. When you remove other canes, be sure to leave at least two buds on four canes to develop into healthy canes for next seasons crop.

An excellent publication for further in depth reading and as a handy reference for your gardening library is “Fruit Production for the Home Gardener” available from Penn State Extension.

Bill Lamont is professor emeritus in the department of plant science at Penn State and can be reached by email at wlamont@psu.edu.