The perfect fit

With the demand for blueberries continuing to be strong, it bodes well for growers to try to extend the season for growing and marketing this delicious, nutritious fruit. In the northern climate, it means having berries ripen later in the season, i.e., early fall, when fewer berries are flooding the market and involves simply growing late season varieties right in the field.

In the warm, southern climates and out west, it’s the reverse; growers need to tap into the early market for berries when demand is higher than supply. However, it’s a little more complicated for these growers than simply choosing late season varieties like they do in the North. While choice of variety is important, covering the crop with high tunnels is what is really needed to reap earlier blueberries that demand a higher price.
 

High-tunnel growing

Growing blueberries under high tunnels, while relatively new in North America, is old hat in some European countries, like Spain. Based in part on this knowledge, researchers from the University of Florida (UF), have touted the advantages of growing blueberries under cover in results that were published a few years ago. Now, you might say the proof is in the pudding as one prominent Florida grower, Straughn Farms LLC in Waldo, Fla., has committed 90 acres to growing blueberries in high tunnels.

Through collaboration with staff at UF, including Dr. Paul Lyrene, professor of horticultural sciences, and former UF Associate Professor Dr. Bielinkski Santos (now a private consultant), it can be safely stated that blueberries grown in high tunnels:

• Require much less water to grow and for frost protection
• Yield more fruit at harvest time
• Ripen earlier and can be sold at a higher the price per pound as ones ripening later in the fields
• Are protected from adverse weather conditions.
   

“We tried peppers and strawberries (in tunnels); we learned our lesson there,” says Kyle Straughn, whose grandfather Alto, a watermelon grower, started the blueberry business in 1982 after buying a bankrupt dairy farm. “It was Dr. Paul Lyrene, a blueberry breeder at UF, who worked with my grandfather for years who put the bug in our ear to grow blueberries in tunnels. We wanted to get ahead of the curve, so we went with it.”

Straughn says harvesting blueberries just two to three weeks ahead of the normal harvest period can mean the difference between getting $3 per pound and $6 per pound. A close second to increased profit potential of early berries under tunnels is the emphasis on conserving an increasingly valuable resource: water. Fortunately, water is a cost-effective way to keep blueberries from freezing.

“What wasn’t an issue before but is becoming an issue, is water,” Straughn says. “We use about a third of the water in the tunnels that we used in the field for frost protection. Water is the cheapest form of frost protection. You couldn’t use propane, it would be expensive.”
 

Covering the crop

Straughn says they initially cover their blueberry crop in early November. Overhead sprinklers inside the tunnels provide water when the temperature dips to around freezing. If they decide they must turn them on, they’ll usually do so during early morning hours. A thin layer of ice will coat the foliage, creating a chemical reaction that will protect the plants from the freezing temperatures. He says turning on the sprinklers is a balancing act.

“Timing and decision making is everything (when it comes to protecting plants from frost); you feel that you should do something but sometimes you’re better off doing nothing,” he says.

The tunnels stay on until late March or early April. This helps keep the plants in an evergreen state, which means better flowering and resultant berry production.
 

A significant investment

Of course, there is an investment to be made before you can even consider harvesting the increased profits that are possible with early berry production. Installing high tunnels costs between $20,000 and $30,000 per acre. Also, Straughn points out that some of the mechanized equipment used between rows of field grown blueberries can’t be used between high tunnels because the poles for the high tunnels extend well into the path between rows. This means increased labor costs because of doing things by hand rather than by machine.

“It is very labor intensive, all the machines we’ve used in the rows for harvesting and pruning don’t work in the hoop houses; you can drive through rows but not between the hoops,” Straughn says. He says you must double the revenue to make this endeavor possible.

“Some years it hasn’t paid to have the tunnels,” Straughn says. ”But then one year we lost six percent of our field crop to freezing temperatures, and didn’t lose any in the high tunnels.”

Straughn Farms is still experimenting to discover blueberry varieties that will work best in the tunnels. Straughn says some of the varieties used in high tunnels in Spain and California haven’t performed so well on their farm in Florida. They’re trying several different blueberry varieties, hoping to find the one that has the vigor to produce after 2 to 3 years.

“We’ve got literally hundreds of varieties under tunnels, and we haven’t necessarily figured out the right one. We think we have it figured out and then the next year we’re trying something different,” Straughn says. “It’s so much different from open field than anybody anticipated.”

Neil Moran is a horticulturist and freelance writer based in Sault Ste. Marie, Mich.