Mike Robinson

A desire to crop Honeycrisp trees early in order to profit from high fruit prices can backfire on growers, a horticulturist warned during a panel discussion at the Washington State University Honeycrisp Fruit School last December.

Dr. Terence Robinson, horticulturist with Cornell University, New York, said Honeycrisp trees grow much, much less than other varieties in the first and second years, regardless of management strategies, such as early planting, intensive fertigation, or other efforts to push tree growth. The trees will then fail to fill the canopy, and production will be limited.

“We can never get Honeycrisp to the same height and same canopy fill as we can with other varieties,” said Robinson, who took part in a panel discussion with Mike Robinson, a grower in Washington’s Columbia Basin, and Bruce Allen, president of Columbia Reach Pack in Yakima, Washington. Tom Auvil, research horticulturist with the Washington Tree Fruit Research Commission, was moderator.

At the end of the first year, a Honeycrisp tree has less total shoot length than other varieties, but it sets up with too many spurs in the second year, Terence explained.

If a tree on Malling 9, Budagovsky 9, or other precocious rootstock, is allowed to follow its natural course, it will produce too many fruit and stop growing. Terence said he would like to figure out how growers could harvest some apples in the second leaf while still allowing the tree to grow.

In Washington State, Honeycrisp apples have been selling for more than $50 a box.

“Every grower who plants Honeycrisp fears that in five years the price will be driven down,” Terence said. “So, therefore, they want to get as much out of it as they can, and that greed to get apples in the second leaf overwhelms us. Then the question is, what do we give up when we do that?”

If a tree is growing too vigorously, there are lots of things a grower can do to slow it down, but if it’s stopped growing, the options are limited, he said.

Mike Robinson said he’s never seen a Honeycrisp tree start growing again once it’s stopped.

Allen said he defruits Honeycrisp trees for the first three years. “Even just a few apples will just shut the trees down before you get a full canopy height-wise.”

Nutrition

Terence said fertilizing to push the trees to grow in the first and second years is critical with Honeycrisp. But that has a down side. If the trees are growing vigorously, the first crop will be poor quality and there could be problems with bitter pit because of a low calcium-to-nitrogen ratio.

“My preference is to start with a big tree and push it in year one but start to back down in year two so I can crop it heavily in the third year without having poor quality,” he said, noting that the first crop of fruit might not have the best storability, so it should be sold immediately.

Allen said his standard procedure for establishing a Honeycrisp block is to deep rip the ground and fumigate it, if it is a replant site. If it’s been out of production, he likes to grow a green manure crop the year before planting. He incorporates compost into the soil before planting, aiming to apply 75 to 100 pounds of nitrogen.

After planting, he fertigates through the drip system almost daily, applying a fair amount of phosphorus for the first two weeks and then switching to only nitrogen. He applies 50 to 75 pounds of actual nitrogen per acre, plus leaf feeds, depending on the rootstock and tree spacing, and has found no further benefit from applying rates above 100 pounds.

Mike said his strategy is to fertilize excessively because nitrogen is cheap and poor tree growth is not. He applies 50 pounds of dry nitrogen in the fall and another three or four shots of 50 pounds in the spring and summer along with five or six leaf feeds with three of them containing 10 pounds of urea.

Terence said he supports those kinds of nutrition programs. Though heavily fertilized trees are more at risk of winter damage, it’s preferable to the risk of not filling the space, which is very expensive.

Terence recommends that Honeycrisp blocks be irrigated even in eastern growing regions. However, his studies show no difference in tree growth, whether the fertilizer is applied to the ground or through the irrigation system as long as the trees are well watered.

Nor has he found a statistical benefit from applying foliar feeds or biostimulants. “I continue to spray foliar feeds because I’m afraid not to, but the data don’t show I get much out of it,” he said.

Allen tries a new “snake oil” about every couple of years, and has never found one that’s the magic, silver bullet. “But you keep looking,” he said.

Stop it and crop it

Once the trees have filled their space and start to produce fruit, the nutrition program changes completely, Mike said.

“The intent is to push Honeycrisp in the first two years until they fill the trellis, and then I’m going to put the brakes on and pull the nitrogen off completely. The whole plan is push, push, push, prune off the fruit load, blossom thin, and keep the thing growing, and then stop it and crop it.”

Allen said once Honeycrisp starts fruiting, it is one of the most sensitive varieties he has ever grown in terms of nitrogen inhibiting fruit color development. For bearing blocks, 30 pounds of nitrogen per acre is a lot.

An audience member asked if scion rooting was a good way to enhance tree growth.

Auvil said that, over time, scion rooting will only increase variability of vigor and crop load. “It’s really a bad idea to deliberately scion-root blocks. It’s much more important to do everything possible to get the tree grown before you put a crop on it, and then you won’t have a problem to mitigate.”

Tree training

Mike said he stubs back limbs in the early years using a Dutch cut to reduce the crop. Allen said he also stubs back limbs, even on well-feathered trees. Terence doesn’t like to cut back branches, so he removes entire branches to reduce the bud number.

Any branch that is more than half the diameter of the leader is removed.

Concerning grafted trees, Allen said he’s grafted over old Red Delicious blocks that were on M.106, 111, or 26 rootstocks.

They’ve been reasonably productive, with crops averaging 45 to 55 bins per acre, but they will never achieve the 100-bins-per-acre yields of newly planted blocks. •