What To Consider When Growing Vegetables Under Cover

What To Consider When Growing Vegetables Under Cover

This row of tomatoes with large fruit load is part of an on-going project with DeRuiter Seed Co

This row of tomatoes with large fruit load is part of an on-going project with DeRuiter Seed Co.
for variety trial testing for
semi-arid, high-light regions.
Photo Credit: UA-CEAC/DeRuiter Seed Co.

So you want to grow vegetables in your greenhouse or high tunnel. Where do you start?


For those in the floriculture industry who want to make the switch to vegetables, the biggest thing to consider before getting started is the market. You need to know where you will sell your greenhouse or high tunnel tomatoes, peppers, cucumbers, etc. — whether it is the local grocery store, a restaurant, a farmers market, or CSA (Community Supported Agriculture) program.

Let Market Be The Driver

According to Roberta Cook, a marketing economist at the University of California-Davis, many times companies are motivated by production to get involved in protected agriculture.

“They’re being more production-driven than market-driven, which is typically something we see in agriculture,” she says. She points out the market on the buy side is consolidated, with much of the retail consolidation taking place within the last 20 years. Buyers are interested in suppliers that have the volume to meet their needs, so Cook cautions growers just starting out that without a defined marketing scheme, they will not have access to the large buyers.

“The first thing I would recommend to anybody getting into a new crop regardless of the method of production is doing market research to understand where the market is, who the market is, and whether they have the wherewithal to service the market competitively,” she says.

In addition to the market, you have to look at efficiencies. Cook says an important question to ask is: Can I produce that volume more efficiently with at least part of that production in protected agriculture?

“If the answer is ‘yes,’ it may make sense for you,” she says. “[This is] as opposed to someone just coming in and saying, ‘OK, now I’m going to get into greenhouse vegetable production,’ and start a crop they haven’t worked with and don’t have established buyers.”

Gene Giacomelli

Gene Giacomelli

Gene Giacomelli, director of the Controlled Environment Agriculture Center (CEAC) at the University of Arizona (UA), says the environment of your location must be considered as well. Take note of the weather that occurs in the area, such as cold temperatures, wind, and hail, and understand what you might be up against. He cites the extensive hail that damaged a couple of Village Farms’ Texas greenhouses a couple of years ago as an example of some of the challenges.

“Once you know what your environment is, you can look at what your cost is to grow, and then determine the price point for your product,” he says.

“As a field grower who has lost many crops over the years and wishing I had a greenhouse at the time, I like the predictability of a greenhouse,” Giacomelli says. “You have a lot more possibilities to save your crop and reach a market on a predicted date and to hit the high-price market by timing it.”

From Floriculture To Vegetables

Those possibilities remain for growers coming from the greenhouse floriculture market to vegetable production in a protected culture, except they are faced with a slightly different challenge. According to Giacomelli, these growers are using their traditional floriculture greenhouses and some have noted that vegetables demand more attention and environmental control than flowers.

Some floriculture growers are transitioning slowly to vegetables, and some may eventually leave the floriculture business to grow greenhouse vegetables, he says.

How To Choose Your Crops

Most of the growth in U.S. protected culture vegetables is in fruiting crops, starting with tomatoes and followed by cucumbers and peppers, Cook says. The vast majority of the growth is in tomatoes.

“The tomato market is one of the most competitive of any vegetable crop, in part because there are so many production regions in North America that may be producing at the same times of year,” she explains.

In spite of the saturated market, Giacomelli says we will continue see an increase in greenhouse tomato production, and it is not just the beefsteak tomato anymore. You have much more from which to choose, such as the truss, grape, cherry, cocktail, yellow, and purple tomatoes.

That variety, Giacomelli says that will keep tomatoes as reigning “top crop” in protected culture. That’s not to say, though, that there aren’t several up-and-coming crops moving into the marketplace.

A couple of those are sprouts, microgreens, and “baby” varieties, which include baby spinach and lettuce. What is driving production of these crops is consumers’ interest in fresh salad and the fact that these products are packaged in nitrogen-filled bags to increase shelf life and quality, he says.

Roberta Cook

Roberta Cook

Growing Interest In Berries

Berries in protected culture are another point of interest, Cook explains. Currently, blackberries and raspberries are being produced in protected environments. Where there is potential for growth, however, is in strawberries.

Most straw-berry production in protected culture is in the experimental phase, and part of that is evolving in Mexico, where raspberries and blackberries are being produced, she says.

“One of the factors these berry crops have in common is they’re high-value crops,” Cook points out. “It does increase your cost to grow in tunnels, but they are crops where there is now year-round demand. We cannot grow these crops year-round in the U.S. except for strawberries [within the berry category]. And even in California the volumes are quite low in December and in January.”

Blueberries, Cook continues, are also an up-and-comer for protected culture. They can’t be grown in the open field in the winter, with the exception of Florida, where it is an especially high-value winter crop that needs to be protected from frost damage. “It may make sense for [these growers] to experiment with some protected culture, even though it will be higher cost just because of the market benefits they may achieve,” she adds.

Key Considerations When Growing Under Cover Greenhouse Vegetables November 2015

Blueberries are an up-and-coming, high-value crop to consider for protected culture production.

Words Of Advice

Suffice it to say, if you are going to get involved in protected production or expand your operation, many decisions must be made — from structure to the crops you will grow.

According to Giacomelli, if your goal is season extension, use high tunnels, as they are a low-cost option. If you want to be a year-round producer, however, there are many good U.S. companies who can help you choose the structure that best fits your needs.

He suggests visiting the National Greenhouse Manufacturers Association’s website to learn more about the companies involved in greenhouse design, heating, cooling, irrigation, etc.

“Look at which companies may service your area the best and talk to them about greenhouse design,” Giacomelli says. “Tell them what you want to grow and they may be able to help you, or talk to your local county Extension agent or university researcher if that person is experienced in greenhouse vegetables. Go where the research is being done to see if you can get some advice, and do a lot of reading.”

Giacomelli also says to consider attending the UA-CEAC annual Greenhouse Short Courses.

Labor Considerations

Most of you coming from open-field vegetable production have employed some type of labor force. The situation is similar in protected culture such as a greenhouse, especially if you are thinking of expanding. In protected cultivation, however, the issue isn’t necessarily harvest labor. The need is for someone in a management position.

According to Giacomelli, you have to do your homework before expanding to see if your business can carry the weight of an additional full-time employee in a management role. If you hire that additional manager, you risk failure because of the increased payroll strain. Plus, he says that person has to be as dedicated as you are to your operation, and that is very difficult to find.

“That is why when we see 1/2-acre ‘mom and pop’ operations expand to more than 2 acres and bring in someone from the outside to help run the greenhouse, they risk failing because you have that load of the extra person,” he explains.

Plus, Giacomelli says we are limited in people who are educated and experienced on the real workings of the greenhouse crop production facility.

“Most greenhouse operations hire labor positions, not managerial positions. We need growers who can manage a greenhouse,” he says. “We don’t have enough of them.”