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Trees & Shrubs: PRUNING

Pruning Fruit Trees and Small Fruit

By Sue Gray, OSU Extension, Horticulturist
Spring 2003

February through March is an excellent time to prune fruiting plants. Most gardeners, however, have no idea where to begin. First, we must recognize that all flower buds that bloom and make fruit were developed last summer. So, no matter what we cut off of the tree, we are removing some potential for fruit. But, this is necessary to encourage vigorous new growth next summer, allowing for more fruit buds to set the following year.

Most tree fruit are cut to encourage new growth, but also to keep plants short and stocky. This helps the tree to bear a fruit load without broken branches. Most small fruit plants, such as grapes, blueberries and blackberries are pruned to renew the growth.

All fruit plant pruning begins with the three D's: Remove all dead, damaged and diseased wood, as well as limbs that may rub on another, causing damage.

Additionally, any cut under two inches in diameter needs no pruning paint. Larger ones probably don't need it either, but slant their cut so that water does not run into the center of the tree, causing rot to begin.

{Photo 1a: flower buds; photo 1b: Proper Limb Cut.}

Beyond those little tips, each tree or shrub has it's unique pruning needs. So, here's a quick rundown on how we prune the following: apples, pears, peaches, other stone fruit, grapes, blackberries and blueberries:

Apples

Train apples to a Christmas Tree shape, spindle like, with a central leader. Take no more than 15% of last year's growth off any time you prune. Spread young branches to a 45 degree angle to encourage fruiting growth and strong limb structure. Most apples do best with five to seven scaffold limbs.

Pears

Pears are pruned just like apples. However, be diligent in their young life about spreading and weighting limbs to achieve the 45 degree angle crotch. Also, never severely prune a pear, it will send up vigorous suckers, leaving the tree more susceptible to fire blight disease.

{Photo 2b: Training Pears; Photo 3: Limb Spreaders on Tree.}

{photo 3: Limb Spreaders on Tree.}

Varieties susceptible to fire blight, such as 'Bartlett' should be pruned with a 10% bleach solution nearby. Dip pruning blades after each cut to sterilize them. This will prevent spread of the disease from among limbs or between individual trees.

Peaches

An old horticulture professor once gave me the following advice on pruning peaches: "Prune it to open it up so that you can throw a cat through the middle without him grabbing hold of the limbs!!!!" In other words, peaches grow best with an open center. Visualize your hand upturned with fingers curled slightly upward….that's how a peach should look after pruning.

To encourage vigorous new growth, we remove about 30% of growth from a peach each winter. This makes them look like they've had a crew cut. But, peach buds mostly set on one year only wood. For this reason, we need to be constantly forming new wood on the tree.

{ Photo4: Peach Tree with Open Center.}

A portion of one year old wood is certainly left on to allow for flowering and fruit, while the height is controlled by heading limbs back to a manageable size.

Other Stone Fruits

Apricots, cherries and plums are all related to peaches and nectarines in that they have a pit in the center of the fruit. However, pruning is much simpler We are not as concerned with scaffold limbs or height control with these three types of trees. Why? Because the fruit load is lighter and because their growth is sometimes a bit slower and more compact.

{Photo5: Plum Tree.}

First, prune out the Three D's. After that, just remove a few tips of limbs that may be getting too tall. Also, remove limbs that look like they'll eventually cross over and rub another limb. Last of all, trim up any limbs that make the tree to low to mow under.

Grapes

Ah, the grape! Be ruthless with the vine pruners to harvest abundantly from year to year. Using hand pruners and bypass loppers approach the vine. (short handled loppers are called vine pruners) Size up the situation: Has it grown quite vigorously? Or, is it looking a bit weak?

We generally remove about 90% (yes, that is 90), of last year's growth. This keeps the vine productive and in bounds.

First, remove any of the Three D"s. Then, take off all growth that is older than one year. This older growth will be dull brown, with, peeling bark. One year old wood is red and satiny. Most of it can come off as well, leaving just four "canes" to stretch along the fence wire.

As one year old wood is selected for removal be sure to leave renewal spurs. These are four short branches of one year old wood that will sprout out new canes next year. Cut each spur back to two or three buds each.

Photo7: Renewal Spur.

Grape cuttings are easy to root. Snip some of the one year old wood into 12 to 18 inch long cuttings and pot them up for sharing with friends. Rooting occurs in a few weeks in a greenhouse or cold frame.

Blackberries and Raspberries

Brambles grow on a two year cycle. The first year, a sprout emerges and just grows leaves. The second year it flowers and bears fruit. After harvest it begins to die. Remove two year old canes after harvest. Cut them all the way to the ground, being careful to not nick nearby one year old canes.

{Photo8 - Raspberry Plants. Note older, yellower wood with harvest about to end. Cut old canes to the ground.}

During the growing season tip back one year old canes to make them branch out. This may be done two or three times throughout the growing season.

Note: Fall fruiting raspberries can grow leaves and flower buds all in one season. After harvest is over, during the dormant season, the entire mess can be mowed down. You'll have no spring harvest, but pruning couldn't be easier.

Blueberries

Pruning blueberries is just a matter of removing old, unproductive wood. A productive blueberry shrub will have a bright red cast to the branches in winter. This is because young branches are red. Old wood is a dull brown. If a blueberry bush has more brown branches than red ones, then it needs renewal. Begin by cutting older wood back to the ground. If new wood is getting too tall, or is not branched enough, wait until after harvest to prune. At this time, we can tip back the growth and encourage side shoots. If pruned before flowering and fruiting, we may remove too many buds, reducing the number of berries that we harvest.

{Photo 9: Blueberry Plant.}

Note: Blueberries that are newly planted need at least three seasons to establish roots. Remove any flowers the first three summers to avoid diverting energy away from establishment.

{Photo 10 - Blueberry plant with flowers being removed.}

Pruning fruit is not difficult. It is a skill that is easily learned. Just think ahead, visualizing what needs to grow on the tree or bush in the future.