PULLMAN — Researchers from Washington State University (WSU) have found that mechanical hedging can be beneficial to fruit growing in the state.

Karen Lewis, WSU extension specialist in Grant County, led the apple trials. These trials took place on commercial orchards in Quincy and Mattawa. Mechanical hedging uses motorized arms to shorten branches in an orchard and create a narrow canopy. Narrowing the canopy of the trees opens up the fruit to more sunlight, which improves the quality, Lewis said. The narrower canopy created by hedging also allows for more room for other equipment, such as machines used for harvesting, she said.

Through the trials, Lewis found that mechanical hedging was between 40 and 70 percent faster than hand pruning. She also found that shortening the branches did not reduce the return bloom or fruit quality.

There are some potential problems that can arise with this technology. If hedging begins late in the season, fruit that has only ever been in the shade could suddenly be fully exposed to sun, causing the fruit to burn, Lewis said. Another problem can occur if hedging is done on trees that are too old. The hedging may reduce the volume of the trees to the point where fruit yield may drop.

Lewis said there also is a misconception that mechanical hedging is used primarily to save money. She said, while it is more efficient, reducing costs should not be why growers purchase hedgers.

“That’s not the reason to do it,” she said about trying to cut costs. “The reason needs to be to improve fruit quality.”

The trials for all three fruits took place on four different orchards with four fruit companies. Lewis said two of those companies purchased their own hedgers.

Lewis said researchers and growers will need to continue to monitor the results. She said European countries that have used hedging for a long time have seen that after eight to 10 years there seems to be a trend toward reduced yield.

She said knowledge of this potential can be used to prevent this outcome.

“You have to be an alert grower,” she said. “Mechanical hedging is not a silver bullet; we don’t have any silver bullets.”

Lewis said hedging should be used as one tool for maintaining canopies while keeping a balance of structural and fruiting wood.

In the pear trials, held in Monitor, Wash., a combination of mechanical hedging and hand pruning produced a greater proportion of large fruit than hand pruning alone.

In the cherry trials, held in Prosser, Wash., mechanical hedging was 29 times faster than hand pruning alone and 17 times faster than a combination of the two.

Trials for hedging also took place in New York and Michigan, with similar results, Lewis said.