by Tamara Scully

Amy Ivy of Cornell Cooperative Extension, Eastern New York Commercial Horticulture, and Mike Davis, manager of the Cornell Willsboro Research Farm, have been conducting high tunnel research to help growers determine which warm season plants do best in high tunnel conditions compared to field-grown counterparts and how best to grow those crops to capture their market value.

Tunnel Tomato System
Tomatoes are a high value crop and getting these to market first is often the instigation for growers to move them into high tunnels. Cherry tomatoes are typically the earliest type to market. They also are such vigorous growers that managing them is often left to chance, and they are forgotten as the season progresses. But cherry tomatoes have the potential to be a long-season lucrative crop if their growth is managed, so that picking them isn’t a time-consuming chore.

Ivy’s research compared three types of pruning systems on indeterminate cherry tomatoes grown in high tunnel production. The first single leader system pruned the tomatoes to a single stem, pinching out all suckers. The double leader system involved keeping the deep “Y” that all tomatoes develop at the first sucker, under the first flower. Ivy pruned all suckers and leaves off prior to this point, and then continued pinching out suckers as in the single leader. The third method – the multi-leader system – was pruned to a double leader, but suckers were allowed to grow after this initial pruning. Single leaders were planted 12 inches apart in the row, while the other two systems were planted at 18 inch spacing.

The multi-leader system was hardest to harvest due to receiving the least amount of pruning, making picking more difficult as the vines grew. The single leader took the least time to harvest but required more pruning time than the multi-leader. The multi-leader yielded about 283 pounds of tomatoes over the season measured, while the single leader system yielded 226 pounds. The multi-leader’s net revenue, after accounting for the labor of pruning and of harvest, was $967 while the single leader’s net revenue was $785 after labor for pruning and harvest was considered.

It was the double leader system that offered the best balance of yield to labor. The net revenue from cherry tomatoes grown in this system was $1,106. All three systems yielded more crop in late August than could be efficiently picked. The single and double leader were equivalent in harvest labor efficiency, with the multi-leader being much less efficiently harvested, Ivy said.

Pepper Perfection
Are specialty pepper varieties, designed for greenhouse production, worth there cost and upkeep in unheated high tunnels? Ivy selected the Sprinter cultivar of gourmet pepper, designed for greenhouse conditions, and grew it in the high tunnel alongside the standard Red Knight bell pepper. She also planted Red Knights in the field.

The growing season was colder than usual. Four inch transplants were used. Tunnel production began a few weeks earlier than did field production, with a Sept. 15 start for Sprinter and an Aug. 8 start for Red Knight. The field-grown Red Knight did not begin to bear until early September. The Sprinter, which needs heat, probably had a delayed start in the tunnel due to cold weather.

The field yield of Red Knight was much less than the tunnel yield. The killing frost on Oct. 11 ended production. But in the tunnel, Sprinter kept bearing – out-producing the Red Knight, which significantly slowed down – and continued producing into mid-November.

Ivy spoke of “the vigor that you get with these greenhouse varieties,” and explained that Sprinter peppers were pruned using the double leader method recommended for the variety by the seed company, Johnny’s Select Seeds, as well as a traditional stake-and-lead method.

The double leader required increased pruning time. Labor was “a tedious process,” Ivy said. This method resulted in yields of 4.5 pounds per plant. The stake-and-lead plants had increased yields, of 5.8 pounds per plant.

The double leader system did have larger fruit, and fruit remained plentiful on Nov. 3, but due to lack of heat in the high tunnel could not ripen. If this had been a heated greenhouse, the Sprinter on the double leader would have continued to produce, upping its yield.

Early Warm Season Crops
With the challenge of knowing what to plant in the high tunnel being one familiar to many growers, Davis set out to quantify which types of warm season vegetables are worthy of tunnel production.

“To what extent can we accelerate our harvest compared to the same crops grown in the field?” was the premise, Davis explained. Researchers also looked at the use of row covers in this equation, both in and outside of the high tunnel.

In attempting to determine if high tunnel production resulted in an earlier harvest, the researchers transplanted zucchini that did not require bee pollination into the tunnels on April 23 and in the field on May 17. Row covers were used on some field plots until June 14, and on some tunnel plots until the temperature in the tunnel was above 80 degrees Fahrenheit. It was a cool and wet spring.

Field zucchini plants were much smaller than those in the tunnel, and weeds were prevalent in the covered rows outside. There was a slight statistical difference in yield, with the covered field rows producing more fruit than uncovered field rows, even with the weed pressure seen. In the tunnel, there was no statistical difference between covered and uncovered, and the tunnel production yielded more fruit than field production across all methods.

“Part of that is just a function of more time,” Davis said.

Beans were not found to be worth the tunnel space, as they “are notoriously able to catch up,” he said. “Beans are not the best use of tunnel space.”

In the trial, bean production was not much different between tunnel or field, or between covered or uncovered rows in either system. The first beans seeded in the tunnel on April 20 did not germinate, probably due to cold soils, so the tunnel crop wasn’t replanted until a few days before the field crop was sown.

Peppers were also transplanted, and “really mimicked what happened with the zucchini,” Davis said. “We can get that accelerated production in the tunnel.”

The tunnel peppers also had much less culls than the field grown peppers, which suffered from sunscald and blossom end rot. The leaves are bigger in the tunnel, which could have provided fruit with some protection from sunscald, as the tunnel covering itself may have done. In the field, the blossom end rot could have been a factor of windy days interfering with irrigation and fertigation management, causing fertility concerns.

High tunnel production of peppers starts off slowly in the early season, however. “That early planting date is tricky, especially with the peppers,” Davis said.

Deciding which crops to grow under cover to gain the greatest advantage without wasting valuable tunnel space on crops that will yield as well outdoors and reaping the highest profit from high tunnel production systems can be daunting.