Many growers in Tasmania are using the Kym Green Bush (KGB) training system for cherries, which is a modification of the Spanish Bush. It involves heavy pruning in the early years to establish the bushy tree form, but that delays production.
At the Grove Research Station in Tasmania, senior horticulturist Predo Jotic is demonstrating to growers how to modify the Spanish Bush to produce earlier crops.
Jotic said Green’s philosophy is that growers should be patient about cropping and wait for a big crop in year four. But Jotic feels that if you can prune less and crop a cherry tree in year three, you might as well do it. Plus, in Tasmania’s cool climate and poor soils, the rate of growth of the cherry trees is generally too little to benefit from the aggressive pruning that the KGB entails.
He is testing a system he calls the Intensive Spanish Bush, which involves planting the trees at higher densities and pruning less in order to improve the precocity of the planting.
In a trial with Lapins and Simone on Colt rootstock, Jotic planted trees 1 or 2 meters (3.3 or 6.6 feet) apart with 4.5 (15 feet) meters between rows (1,111 or 2,222 trees per hectare). The planting will get off to a better start if the nursery trees have plenty of feathers, he said. A bench-grafted nursery tree might have six to nine branches.
"You prune those down to six inches at planting and then let go," Jotic explained.
At the end of year one, one or two limbs are cut back to a stub to improve light penetration, but minimal pruning is done other than that. In this system, the trees will grow to have about 12 to 15 limbs—half the target number of limbs of the KGB.
Jotic compared one-year-old grafted trees and two-year-old bench-grafted trees planted at the same spacings. At 1,111 trees per hectare (450 trees per acre), the one-year grafts produced 4.6 tons per hectare in year three, while the two-year-old feathered nursery trees produced 7.6 tons per hectare. At 2,222 trees per hectare (900 trees per acre), the one-year-old trees produced 7.3 tons per hectare in the third leaf, compared with 12.9 tons for the two-year-old trees.
Jotic concluded that more trees, better nursery trees, and lighter pruning can generate higher early yields.