Double-axis system shows benefits

North Americans in the foreground Sigifredo Corral, left, and Martin Leighton compare notes on the impressive wall of Pink Lady apples.

Published January 15, 2011

The biaxis or double branch tree, with its ease of training to a fruiting wall, is being studied throughout Italy in different tree fruit crops and settings. In Italy, the two-branch tree is patented by Vivai Mazzoni Nurseries, and sold under the trademarked name Bibaum, which means two trees in German.

“The tree fruit growers in South Tyrol prefer to use the German language, so the name is German and not Italian,” explained Carlo Mezzola of the Mazzoni Nurseries near Bologna.

For the last five years, Bibaum trees have been planted in tree-training trials in northern Italy to compare the fruiting wall and its mechanization advantages to the slender spindle system, the most popular orchard system in the country. Bibaum trees, in addition to ease of tree training (little, if any limb bending is necessary), require about 25 percent fewer trees than a planting of vertical axis trees, according to Mezzola.

Growers, too

In addition to running a nursery, the Mazzoni family grows about 500 acres of apples, pears, and other tree fruit, and commercially packs about 130,000 tons of fruits and vegetables. In a 65-acre orchard, Bibaum trees have been studied for five years, planted side by side with the spindle system for comparison.

Pink Lady and Rosy Glow have been planted on Malling 9 NAKB-T337 with 1,000 trees per acre at a space of nearly 11 feet between rows. About 2.5 feet are between each leader of the axis of the Bibaum tree. They have used both 4 and 4.8 feet spacing between trees. Trees are trained to a height of ten feet on four wires.

“It truly is a wall of fruit,” Mezzola said. “In terms of tree training, we just need to wait for the fruit to grow.”

He explained that the two axes of the tree act like brothers. “They don’t compete against each other because they are two of the same plant. They don’t fight each other, they just fight with the other axes from the other trees.”

In the second leaf, Mezzola said they aim for 20 to 25 fruit per axis, and expect to pick 25 to 30 tons per hectare, the equivalent of 25 to 30 bins per acre. Last year, in a ­second-leaf Rosy Glow planting, they averaged 40 bins.

Productivity in the fruiting wall has been high, thus far. In fourth-leaf Pink Lady, they picked 65 bins, and in the fifth-leaf block, they picked 80.

Mezzola said there was less sunburn in the Bibaum than in the spindle, size and color was more uniform, and they can pick fruit in one pass, compared with two or three passes in the spindle. He noted that the fruit shape on a Bibaum tree is slightly longer than on other training systems, and there is no russeting in the Bibaum trees.

They use 15 orchard platforms in their 65-acre block, well more than the industry average of one platform per 25 acres, because of the need to get fruit harvested before fall rains come and muddy the orchard floor.

Physiological aspects

Mazzoni Nurseries’s Dr. Michelangelo Leis explained that good light interception is one of the main advantages to the biaxis tree structure. Fruiting branches are short and uniform throughout the tree, with few suckers. Biaxis shoots are shorter than those on a central leader tree, but the number of shoots is higher, resulting in higher ­numbers of buds.

Though the two axes are smaller than a central leader trunk, he said that if the diameter of the two are added together, the trunk would be 30 percent larger. “That means increased canopy without impacting the light interception. You have more leaves but less shadow.”

A Bibaum tree costs about 25 percent more than the cost of a well-feathered vertical axis tree, but the number of trees required to be planted is about 25 percent less, so costs are similar, he said. Tree costs vary, depending on variety and royalties, but the average cost for a Golden Delicious feathered tree is around $6.30 compared to a Bibaum tree cost of $7.85, including the Bibaum royalty.

Mazzoni Nurseries produced about 600,000 Bibaum trees last year. Leis estimated that nearly 2,500 acres of Bibaum trees have been planted in Italy. Trials in peaches and plums are also under way.

Mazzoni Nurseries is part of an Italian consortium of nurseries known as the Center for Variety Innovation or C.I.V. The consortium also includes Salvi Nursery and Tagliani Nursery.