Small trees with big potential

October 8th, 2021

Nick Howell inspecting a growing apple tree supported by wire fencing
Nick Howell, superintendent of the Horticulture Research Station, inspects plant growth in the new orchard. Even though these trees were just planted in May, he expects they will produce a partial apple crop next year.

By Amber Friedrichsen

Trees in the newly planted orchard at the Horticulture Research Station will soon be bursting with apples thanks to an innovative growing technique.

Hundreds of apple trees were planted earlier this spring at Iowa State University’s Horticulture Research Station north of Ames. The chosen apple varieties were grafted to dwarfing rootstock and are already near their maximum height – a mere eight feet compared to the 50-foot height of traditionally grown apple trees.

The trees are growing in a tall spindle system, which consists of rows of wire trellis on which the trees are planted and supported. The uppermost wire is about eight feet high, and trees from dwarfing rootstock will not grow much taller than this. When they reach this point, trees will stop growing vegetatively and use their energy to produce apples instead. 

Nick Howell, superintendent of the Horticulture Research Station, said the tall spindle system has already been implemented by many commercial growers. The new orchard will be used to demonstrate the best practices for this growing system to apple producers in Iowa.

“The tall spindle system is becoming widely used, and we need to better understand the management that comes with it,” Howell said. “With this system in place, we can conduct more relevant research on it for the growers we serve.”

One of the benefits of the tall spindle system is the young trees start to put on fruit sooner than traditionally grown orchards. Howell compared the establishment period of trees from dwarfing rootstock to that of the trees from semi-dwarfing rootstock also grown on the farm.

“We are going to get our first partial crop next year, and the following year should be a full crop,” Howell said. “That is about one-sixth the amount of time of our original semi-dwarf root stock system, and on a per-acre basis you actually end up getting the same or better harvests.”

Brandon Carpenter, agricultural specialist, selected the new rootstock for many reasons. In addition to being compatible with the tall spindle growing system and its propensity to put on fruit, the rootstock that was planted has mild fire blight resistance. This disease ravages apple trees if it affects their roots, but having resistance will protect them against such.

Carpenter also strategically designed the orchard, spacing the rows of trees far enough apart so a tractor can easily drive in between, which will maximize spraying efficiency. He also noted how important row spacing is for the amount of sunlight trees receive.

“Tree height should be about 90% of row width,” Carpenter explained. “The orchard is oriented north to south, so if we have a 12-foot row and our trees are about 90% of that in height, the canopy will get at least six to seven hours of sunlight per day.”

The new trees have already soaked up the sun and have started producing buds on some branches. Carpenter said these buds are building cells and storing energy to grow next year’s apples. A fruiting branch will be productive for about five years, and then will need to be pruned. Since the treetops won’t be too far out of most people’s reach, the pruning process will be much easier.

According to Carpenter, it takes an experienced pruner about 45 minutes to trim a tree from semi-dwarfing rootstock. However, it would only take about three minutes for the same pruner to trim a tree from dwarfing rootstock in a tall spindle system. Carpenter and Howell expect the new orchard will require significantly less labor.

Picking apples will be easier, too, especially since there will be no need for a ladder. In the growing seasons to come, the fruit harvested from this orchard will be sold to ISU Dining and other wholesale sources. The Horticulture Research Station also markets apples directly through their online produce sales.

Despite faster apple production, pruning and picking, the new orchard’s lifespan is limited. Trees from dwarfing rootstock are only productive for about 20 years. Fortunately, Carpenter does not consider this a problem. Consumer choice dictates production, and shoppers frequently change their minds about their favorite apple.

“People determine what we eat, and they are constantly looking for new varieties,” Carpenter said. “People’s taste will change in 20 years and then we will have to replace our trees with something else. Longevity is not really a concern anymore.”

For this reason, Carpenter was not afraid to plant 10 relatively unknown varieties in the new orchard: Rosalee, Summerset, Ludacrisp, Sweet Zinger, Evercrisp, Autumn Crisp, Rising Sun Fuji, Brooksfield Gala, Crunch-a-Bunch, and Baker’s Delight. The demand for these varieties doesn’t compare to that of Red Delicious or Honeycrisp, but it might not be long before consumers seek a different slice.

Students spent a rainy day last May planting hundreds of apple trees in the new orchard at the Horticulture Research Station. Four trees were planted between each of the posts.

Rows of growing apple trees supported by wires connected to wood posts
The trees in the new orchard will not grow much taller than the top wire. Even so, they are expected to produce as many, if not more, apples than trees in other growing systems.