Don’t be surprised if berry growers in the Southeast start to develop “tunnel” vision.

THE FLORIDA variety Strawberry Festival works best in a high tunnel program in North Carolina.

That’s because the new technology called “high tunnel production” appears ready to help produce higher yields and better quantity of strawberries, blackberries and it should also greatly extend the production season and perhaps at the same time widen the marketing window, allowing growers to capture better prices.

What is a high tunnel?

“I call it a poor man’s greenhouse,” says Joe Hampton, superintendent of the Piedmont Research Station in Salisbury N.C., where much of the research is going on.

“It will have a hoop structure, with a frame of thin wall pipe and plastic covering. It looks a bit like the greenhouses that tobacco growers use to produce transplants.”

No heat is needed: It takes advantage of passive solar collection, says Hampton.

“Here at the station, we use row covers inside the tunnels to keep the plants warm. All the tunnels are watered with trickle irrigation so that no moisture ever gets on these plants.”

This system requires no energy. But it requires a lot of management, says Hampton. “For instance, if the temperature reaches 60 degrees on a winter day, it can get too hot in the tunnel. You have to take action.”

The major benefits of high-tunnel production are:

• A much longer season. High tunnel strawberries were producing fruit for more than 40 weeks this year at Salisbury and the North Carolina research station at Laurel Springs, says Hampton. And that may not be the limit.

“We terminated our high tunnel plots in June, but we probably could have kept going,” says Hampton. “The plants were still producing at that time. The purpose of this research was to extend the production season. It has certainly accomplished that.”

An average strawberry plant produces six to seven weeks before warming temperatures bring its production to a halt.

• Production at untraditional times of the year. “Strawberries produced in January and February could potentially have much higher value compared to those we sell in May,” says Hampton.

• A much, much larger yield. “We have had some plots where the yield was three times the normal level,” says Hampton. “This would not be an unrealistic goal with this technology.”

But a very high yield is going to be a necessity to make high tunnel berries pay. Hampton estimates the cost of installing a system like this at $35,000 an acre.

Not just every strawberry variety will perform satisfactorily in a fall production program.

“If you are looking at fall production in a high tunnel program, the Strawberry Festival variety from Florida is probably the best overall because of its consistent high quality production,” says Jim Ballington, North Carolina State University plant breeder. “The Sweet Charlie variety will also work, but not many others would be a good choice.”

North Carolina Extension Horticulturist Barclay Poling says that Strawberry Festival has “plump, beautiful fruit and 6 to 8 inch stem. That makes it popular for stem berry packs, which get the best price in the strawberry market.

“This is a popular berry for Valentine’s Day, perfect for dipping in chocolate.”

Strawberry Festival has never produced well in conventional cultivation in North Carolina, but has responded well in the high tunnel environment, Hampton says. In a tunnel system, it bears over an extremely long time and produces excellent quality. “It is a very desirable berry,” says Hampton.

There are still a number of challenges to succeeding at high tunnel strawberry production, says Jeremy Pattison, North Carolina State University horticulturist.

“Among them are short day lengths and extreme fluctuating temperatures,” he says. “We are starting to re-examine how the strawberry plant grows and allocates energy to various plant parts in order to increase production in this system.”

Pattison is now directing the North Carolina strawberry breeding program. Ballington, who had been handling it, has moved to directing a new program for breeding new varieties of muscadine grapes for Tar Heel vineyard operators.

Whatever variety you are growing, high tunnels definitely improve the shelf life of the fruit, says Ballington. It is a controlled moisture environment. “If you produce in a high tunnel, rain is not that much of a factor.” he says. “You don’t get the fungus problems you have in conventional strawberries.”

High tunnel production may well be popular among raspberry and blackberry growers also, says Hampton.

“With blackberries and raspberries, you are dealing with a different set of issues than with strawberries,” says Hampton. “For instance, in a wet season, fungal diseases are a real problem in conventional cultivation of these types. But this problem is eliminated in high tunnels because they prevent any rain on the fruit. If we can keep the fruit dry, we can get higher quality fruit.”

North Carolina Commissioner of Agriculture Steve Troxler is high on high tunnels. At a recent field day at Reidsville, he said, “Tunnel technology is going to open up a lot of avenues for other fruit and vegetable production that we’ve never been able to do in North Carolina because of our growing season. With our proximity to markets on the East Coast, this sets North Carolina up to be a major player.”

Troxler, a former fruit and vegetable grower himself, is delighted at the possibility of a winter strawberry crop. “When you’re getting fresh North Carolina strawberries in November and December, you feel like you’re stealing,” he says.

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