Innovative High Tunnel Tomato System Controls Diseases Organically

For the first time, tomato growers using high tunnels in western Washington can manage one of the most serious plant diseases organically, according to plant pathologist Debra Inglis.

Insight into late blight management in organic agriculture is one of the many outcomes of a three-year project led by Washington State University (WSU). A team of 17 scientists tested five biodegradable mulches — alternatives to the traditional plastic mulch covers that suppress weeds, maintain soil temperatures, increase plant production, and shorten harvest time — in open fields and increasingly popular high tunnels.

Production and disposal of plastic mulch, which is used to enhance the growth of several hundred thousand acres of specialty crops in the U.S., pose environmental and financial challenges to growers who need to find a way to recycle the material.

WSU researchers Inglis and Carol Miles led the USDA National Institute of Food and Agriculture (NIFA) Specialty Crops Research Initiative (SCRI) project. Their leadership earned them the 2013 NIFA Partnership Award for Innovative Programs and Projects, which they accepted in Washington, D.C. on behalf of their SCRI team in November. Team members across six institutions conducted trials with biodegradable mulches in high tunnels in Texas, Tennessee, and Washington.

“We found that high tunnels can produce higher tomato, lettuce, and strawberry yields relative to the open fields in the three field study regions,” Inglis said. “Higher crop yield can translate to increases in profitability depending on the crop’s production costs and market price.”

The higher temperatures, better ventilation, lower humidity, and reduced leaf wetness inside the high tunnels also help combat the water mold that spreads late blight infection to tomatoes.

The diverse research team included economists, horticulturists, plant pathologists, sociologists, biological systems engineers, and soils and textile scientists. Looking at the relationships between five different types of mulches in the high tunnels, the project used the expertise of textile scientists from the WSU Department of Apparel, Merchandising, Design and Textiles (AMDT). They tested for key changes in the mulches over time, including changes in weight, thickness, flexibility, pore size, and color.

Scot Hulbert, interim chair of the WSU Department of Plant Pathology, noted that the “NIFA is now the chief institute in the country funding agricultural research and this (award) means they recognize that we are doing it right.”

Inglis said she and Miles are honored to receive the award and grateful to each of their team members – including Tom Marsh and Suzette Galinato in economic sciences, Jessica Goldberger in crop and soil sciences, and Hang Liu in AMDT – as well as former graduate students Jeremy Cowan and Marianne Powell.

Source: Washington State University

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High tunnel tomatoes outperforming field tomatoes

Over the last 2 years – hot and dry in 2012 and cool and wet in 2013 – tomatoes grown in high tunnels have outperformed field tomatoes. The high tunnel environment provides more heat early in the season and therefore earlier harvests. In the summer, the high tunnel provides a rain shield and protection from storms, reducing disease pressure dramatically and eliminating fruit cracking. Later in the year, the tunnel again provides extra heat, extending fall production. While there is some loss of fruit set in the heat of the Summer, reducing August production, fruit quality is still superior.

One researcher likened the high tunnel to a “desert environment”. I like to think of it as creating a “Mediterranean climate” which is very conducive to growth of many vegetables. In addition to the reduction in disease pressure, insects are also less of a problem as many do not prefer the tunnel environment (spider mites are an exception to this and mite pressure often increases).

Single early spring tomato plantings will produce well into August, decline, and then pick up again in September with determinate slicer types. Indeterminate types (most cherry tomatoes, some slicers) may get so big that they are hard to manage late in the year. Replanting after early production peaks (late July) can be another tool to get higher fall production and manage plant size.

For direct marketers, the high tunnel is becoming an essential tool for tomato production. We are fortunate to have several universities in the region that conduct tomato trials in high tunnels. In particular, Penn State has good trial data and resources for high tunnel tomato growers.


Source: University of Delaware

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Experience with high tunnel production

Posted on January 7, 2013 by Ron Goldy, Michigan State University Extension

Tomatoes are usually the crop of greatest interest to many tunnel producers, but other crops perform well and should be considered, including many flowers, leafy greens, herbs, cucumbers, pole beans and lesser known crops like okra.

Even though the main crop in our tunnel trials at the Southwest Michigan Research and Extension Center(SWMREC) has been tomatoes, we have planted other crops to observe how they perform. Vegetable crops performing consistently well include beit alpha cucumbers, pole beans (Photo 1) and okra.

Pole beans Cucumbers
Photo 1. High tunnel-grown pole beans (left) and cucumbers (right). Photo credit: Ron Goldy, MSUE

Cucumbers need extensive training and support just as in greenhouse production. Pole beans make a good follow-up, late season crop after the main crop is harvested. They have no trouble finding and climbing support strings, but most pods need harvesting from a ladder.

Okra does well because of the increased temperatures and is easier to harvest since the tunnel conditions extend internode lengths. Eggplant does well but gets tall, bushy and hard to manage; a reduced fertility program may be needed. Peppers need additional support since they get tall and easily fall over under the crop load. Leafy vegetables like lettuce and spinach, and herbs such as basil and parsley, have done well. Part of the reason these do well is the plastic covering reduces light by at least 25 percent, creating a partial shade environment contributing to larger leaves.

Certain flower species have done well – others have done poorly. For those that do well, flower color appears more intense and size is larger. Stem lengths on cut flowers are also longer, again due to the partial shade conditions.

Flowers that have flourished include zinnias (Photo 2), some ornamental grasses (Photo 2), snap dragons, statice, sunflowers (not the real big ones), tithonia, gomphrena (Photo 3) and eucalyptus (Photo 3). Those that do poorly generally do not like high temperatures, including dahlia, cosmos, bachelor buttons, delphinium and gladiolus.

Zinnia Ornamental grasses
Photo 2. High tunnel-grown zinnia (left) and ornamental grass (right). Photo credit: Ron Goldy, MSUE

Gomphrena Eucalyptus
Photo 3. High tunnel-grown gomphrena (left) and eucalyptus (right). Photo credit: Ron Goldy, MSUE

Without support, taller flowers tend to fall over and develop crooked stems. A good support system is to simply place 2-foot stakes 1 foot in the ground and stretch chicken wire over the stakes (Photo 4). Flower stems grow through the fence openings and can easily be harvested.

Chicken wire fencing
Photo 4. Snap dragons supported with a 2-foot chicken
wire fence stretched between cedar stakes. Note the stakes
at top of picture (red circles). Photo credit: Ron Goldy, MSUE

For high tunnel research reports generated by Michigan State University Extension at SWMREC, go to theSWMREC Annual Reports website and look at the Annual Reports starting in 2005.

For more information on commercial vegetable production, contact Ron Goldy at 269-944-1477 ext. 207.

More information on high tunnel production

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Greenhouse, even in winter, offers ‘all the fixin’s for a salad’

By Andra Bryan

GALENA, Kan. — Temperatures haven’t risen much above freezing in the past week on a patch of land between Galena and Riverton, but that didn’t stop Tim and Violet Green from harvesting a few hundred pounds of tomatoes.

The bounty was picked from plants that are not being grown hydroponically or in pots. They are growing at ground level in Kansas soil.

Bright red, shiny and the size of grapefruit, the tomatoes were the product of seed the couple started in July.

“We’re the only ones I know of who grow all winter within about 200 miles,” Tim Green said.

Their secret?

“They’re called high tunnels,” he said of the long, rounded structures in which the retired couple also grow several varieties of lettuce, radishes, onions, cucumbers and green peppers.

“We have all the fixin’s for a salad, any time you want it,” Violet Green said.

A high tunnel, or hoop house, is a low-cost version of a greenhouse that can help market gardeners extend their growing season in order to improve the profitability of their farms.

According to the Missouri Vegetable Growers Association, high tunnels can be as simple as pipes or other framework covered by a single layer of greenhouse-grade 4-millimeter to 6-millimeter plastic sheathing. Typically, they aren’t outfitted with electricity for heating or cooling.

In 2001, research by the Bradford Research and Extension Center at the University of Missouri-Columbia evaluated the yield performance of several tomato cultivars within a high tunnel and in the field. The study found that high tunnels significantly enhanced the yield of the tomatoes.

“Based on the result in this research,” the study concluded, “it is possible for a grower to have vine-ripe tomatoes from mid-June until October in the central Midwest by using high tunnels as a complement to field production.”

But the Greens took it one step further. “We installed wood-fired furnaces for times when the temperatures really dip,” Tim Green said. “Our only cost is labor.”

Hence their crop of cucumbers, romaine lettuce, green peppers, and row after row of Red Deuce, Red Bounty and Carolina Gold tomatoes that are producing in late December.

During the recent onset of colder weather, Tim Green has bunked in a sleeping bag on a cot next to one of the furnaces, and he wakes several times a night to feed them more wood.

“When you wake up cold, that’s when you know you need to feed it,” he said.

The Greens use drip irrigation via a network of tiny spouts to each and every plant, and they practice heavy pruning to keep the plants from getting too wet and overgrown.

“They must have good air circulation,” Violet Green said.

The couple have relied on a fair amount of trial and error.

“We learned that in here, the time the plants take to mature is about 20 days longer,” Tim Green said. “The seed packet says 73 days, but in here we plan on 93. There is less light — it’s diffused — so it slows down photosynthesis.”

He also puts into practice years of knowledge learned while shadowing his grandfather, Vert Charles Dudley, starting when he was 6 years old.

“I followed him around his garden north of Stone’s Corner in Joplin,” he said. “We were both having a good time. He was teaching, and I was learning, and neither one of us realized it.”

Tim Green, who worked in the grocery business and for the highway department, described the couple’s level of involvement in gardening as “a hobby that got out of control. It was a job I always would have liked to have.”

There have been setbacks. One year, a new heating system went out the first night it was installed, and they lost everything. This year, the plastic that shielded the cabbage was ripped off in strong winds, which killed the delicate vegetable. But the couple’s persistence has paid off. The Greens are regulars at the Webb City (Mo.) Farmers Market throughout the winter, and they will be there today.

“One year we had more than 2,000 pounds of tomatoes,” Tim Green said. “We sell all we can grow.”

They also will play host to a Feb. 5 winter gardening conference under the direction of the University of Missouri and the Webb City Farmers Market. The conference will be open to the public, and attendees will include market gardeners from as far away as New York.

Come spring, the Greens will begin tending a well-established garden plot north of the tunnels, where 35 rows of blackberry bushes and 12 rows of asparagus plants will demand their attention.

They also will set out dozens of onion plants growing in trays in the smallest of their high tunnels, where neighboring Greek and red lettuce, and radishes now are making a showy appearance.

“Our son, Tim Green Jr., and our daughters and grandkids sometimes help,” Tim Green said. “I’m glad for the help, and glad to pass on what I know.”

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Tunnel Technology Could Help Blueberry Growers

Last Updated: December 06, 2012

Released November 20, 2012

GAINESVILLE, Fla. — Protecting Florida’s $80 million blueberry crop from freeze damage is always a wintertime challenge, but a University of Florida study shows that structures called high tunnels could shield plants from cold and promote earlier fruit ripening.

Though the initial investment can run from $18,000 to $25,000 per acre plus labor, high tunnels deliver better quality fruit, bigger early yields and higher prices if growers beat competitors to market, said Bielinski Santos, an associate professor with UF’s Institute of Food and Agricultural Sciences.

The study, published in the current issue of HortTechnology, tracked two growing seasons on a commercial blueberry farm in Alachua County. The results showed that temperatures outside the tunnels plunged to freezing or near-freezing 61 times during the study. Temperatures fell that low just three times inside the unheated tunnels.

High tunnels may increase air and soil temperatures and protect the plants from wind and rain damage, leading to better flowering and more fruit, said Santos, based at UF’s Gulf Coast Research and Education Center in Balm.

Plants grown in the tunnels produced about 4.5 tons of ripe fruit per acre by the end of March; no ripe fruit came from similar plants grown outdoors during that time. Wholesale prices for domestic blueberries are highest early in the season, starting at about $7 per pound in early April, he said.

“Usually, Florida growers start harvesting in early April,” Santos said. “The more fruit you can harvest early in the season, the more money you’ll make.”

Growers can also save money with high tunnels because they minimize the need for another freeze protection strategy – sprinkling the plants with water to form a layer of ice. In the study, tunnel-grown plants needed about one-tenth the water for freeze protection as plants grown outdoors.

The study involved two blueberry varieties developed at UF, Snow Chaser and Springhigh. Snow Chaser is especially well-suited to life in high tunnels, Santos said.

Made by stretching thick plastic sheeting across an arched frame, high tunnels resemble Quonset huts, he said. Although they have variable dimensions, most tunnels have roofs anywhere from 8 to 20 feet high, with ends and sides that can be open or sealed, depending on the weather.

The technology is popular in other parts of the world but still catching on in the United States, Santos said. In Florida, high tunnels and other protective structures account for about 250 acres of production, mostly for high-value crops such as blueberries, strawberries, tomatoes and bell peppers.

“We always thought it was really complicated and expensive,” Santos said. “So for the past six years I’ve tried to ‘vulgarize’ the technology and develop a system anyone can use.”

Santos said he knows of one Florida blueberry grower using high tunnels; the owners tried 2 acres in 2010 and later expanded to 80 acres. Others have expressed interest in the system.

Santos and co-author Teresa Salame-Donoso, a research associate at the Balm center, have begun collecting data for an economic study on blueberry production in high tunnels.

“We already have some numbers, and we’re collecting the kind of information growers need to make up their own minds about using high tunnels,” he said. “I see more people doing it eventually.”

– 30 –

University of Florida,

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Tastier Winter Tomatoes from Greenhouses Compete with Florida’s Crop


Credit Allison Aubrey / NPR
The taste of Mock’s tomatoes starts with the seed. He uses only organic varieties, including cherry and several heirloom varieties.

Originally published on Thu November 29, 2012 5:37 pm

It may sound like an oxymoron: a delicious local, winter tomato — especially if you happen to live in a cold climate.

But increasingly, farmers from West Virginia to Maine and through the Midwest are going indoors to produce tomatoes and other veggies in demand during the winter months. “There’s a huge increase in greenhouse operations,” Harry Klee of the University of Florida tells us.

And surprisingly, according to skeptical foodies like chef Todd Wiss, the best greenhouse tomatoes come incredibly close to reproducing that taste of a perfectly ripe, summer garden tomato. “It’s amazing,” Wiss says after trying a greenhouse-grownGary Ibsen’s Gold heirloom tomato.

These are a far cry from the flavorless supermarket tomatoes typically found this time of year. When tomatoes are shipped long distances, they’re usually harvested before they’re ripe, which compromises taste. Plus, as we’ve reported before, some of the flavor of those supermarket varieties has been accidentally bred out.

The advantage of the new greenhouse model is that the tomatoes are grown not far from the cities where they’re sold and eaten. And it’s the locavore ethos that’s driving this trend. “What’s harvested today will be delivered to stores tomorrow,” says Paul Mock of Mock’s Greenhous and Farm in Berkeley Springs, W.Va.

Mock’s business has boomed in the last few years, as retailers such as Wegmans and Whole Foods in the D.C., metro area snap up his heirloom and cherry tomatoes, as well as cucumbers and lettuces.

“There were times I had to pound the pavement” to sell produce, Mock says. Now he’s being paid a premium, since “locally grown” produce is in high demand. “I’m finally having fun.”

Now even New Englanders can get summertime-tasting, fresh tomatoes grown not too far from home. In Maine, Backyard Farms is leading the way. And vertical greenhouses are changing the landscape, too, from the new garden spot at Chicago’s O’Hare Airport to Vertical Harvest of Jackson Hole, Wyo., which is just getting started.

So how do they grow? Many of these operations are turning to hydroponic farming, which means the plants are not grown in soil.

As we’ve reported before, soil is one key component of tomato flavor, but it’s not the only one. The hydroponic tomatoes get their nutrients (and fertilizer) from liquid solutions fed directly via irrigation hoses. This typically requires less water and less land than traditional farming.

In fact, it uses up to 10 times less land and seven times less water per pound, according to Kate Siskel of BrightFarms, a company that’s scaling up local produce by building greenhouses at or near supermarkets

Mock says there’s another advantage of indoor growing: “We’ve had very little damage from bugs.” And he’s been able to avoid using chemicals on the leaves or fruit of his plants.

Copyright 2012 National Public Radio. To see more, visit



It’s that time of year when tomatoes usually start to look and taste a little sad. Their color can seem flat, their texture a bit mealy. But there’s a new hope for winter tomatoes.

As NPR’s Allison Aubrey reports, farmers in cold winter climates, from Virginia to Maine, are reproducing the taste of summer 12 months a year.

ALLISON AUBREY, BYLINE: If you want to know what separates a good tomato from a bad tomato, Todd Wiss is a good guy to ask. He’s a professional chef and a tomato lover.

TODD WISS: It’s all about the smell. And you smell it, you smell the Earth, you can smell the soil. You can almost taste it.

AUBREY: I caught up with Wiss in the kitchen of Firefly Restaurant in D.C. He’s the chef de cuisine here, and he goes out of his way to buy local produce. I’ve come with a challenge: Could the tomato that I’ve brought with me today – Wiss has no idea where it came from – taste anywhere near as good as the kind of ripe, summer tomatoes he loves? Wiss says he’s very skeptical.

WISS: This time of year it’s hard. You can just tell by looking at it. If it’s opaque in color it’s probably off.

AUBREY: But when he inspects the tomato that I brought, which is a bright golden yellow, his face lights up.

WISS: Wow, it’s a beautiful tomato. It’s got a nice color to it, nice texture. If it tastes as good as it looks, I think we’re going to be in for a real surprise.

AUBREY: Now, we’ll get to a taste test in a minute. But I should explain that the tomatoes we usually get this time of year are typically trucked in from Florida or other faraway warm climates. And they’re grown from seeds that are known to produce tough tomatoes. It’s intentional because the tomatoes need to withstand the wear and tear of travel and have a very long shelf life, which can compromise their taste.

But this bright yellow tomato we’re about the taste is different. It was grown pretty close to here, not in a field but inside a greenhouse, about a 90-minute drive away in West Virginia. This is something you never would’ve seen here a decade ago. The day I went for a visit, it was cold, there was frost on the ground, and the owner, Paul Mock, gave me a tour.

PAUL MOCK: This is one seven greenhouses.

AUBREY: As we stepped inside, the temperature rises dramatically.

It’s summer all year round here in the greenhouse, huh?

MOCK: Yeah, it’s – yeah. And that’s part of what we have to do. We use propane to heat our greenhouses.


MOCK: And that’s the propane heaters right now.

AUBREY: It’s very humid and bright in here. Rows upon rows of tomato vines stand about eight feet tall. And it smells kind of like a cross between an indoor swimming pool and a garden.

What catches my eye in here are the brilliant colors of the tomatoes. They range from bright golds to deep purple, and Paul shows me some that are ready for harvest.

So, what are you plucking from the vine there?

MOCK: OK, that’s a pink Brandywine.

AUBREY: Ah. And…


AUBREY: I see why it’s called pink Brandywine. It is almost, like, a pink hue.

MOCK: Right.

AUBREY: As he bends down to snag it from the vine, he points out what really makes this operation very different. These plants are not growing in soil. There’s no hint of Earth in here at all. Instead, what I see are narrow irrigation tubes threaded through each pot.

MOCK: And this black line, that’s the irrigation line, like your garden hose, and the plants are getting nutrients through the water.

AUBREY: Mock explains this is what’s known as hydroponics. Everything that a tomato normally gets the soil – including fertilizer and nutrients like calcium and iron – are instead being fed to these tomato plants directly through the hose.

MOCK: It’s almost like you’re getting an IV at the hospital. You’re getting that right, directly in your vein so it’s almost instantaneous.

AUBREY: And Mock says the advantage is that it gives him faster and better control over how his tomato plants grow. If there’s, say, a calcium deficiency, he can correct it much more quickly than if it were soil.

Now, he knows that in the past, attempts at hydroponic tomatoes didn’t always turn out so well. They can be as bland as any winter tomato. But he says there are big differences between those tomatoes and the ones he’s producing. For starters, it’s the seeds he’s using. They’re are all organic – mostly Cherry and Heirloom varieties – and they each produce distinct flavors.

MOCK: Pink Heirloom tomatoes, they’re a little milder. Red is going to be your good, tangy, acidic taste. And then the purples and the black Heirlooms, they’re a little sweeter.

AUBREY: And Mock says the way he maximizes these flavors is by allowing each tomato in his greenhouse to ripen on the vine.

MOCK: If we were to pick a tomato green and allow it to ripen, it would taste no better than a shipped tomato.

AUBREY: What’s typical of tomatoes that are shipped long, long distances is that they’re harvested while they’re still green. They ripen en route and the flavor never fully develops. So the big advantage Mock has is that his customers are all nearby.

MOCK: We are harvesting today so what gets harvested today will get sent to either stores or distributors tomorrow.

AUBREY: And could be on the shelves at markets, such as Wegmens or Whole Foods, by lunchtime. They cost about $5 a pound or more, but Paul Mock says given the demand he’s seen, lots of people seem willing to splurge.

MOCK: Right now, I don’t have enough product for Martins or Safeway and – or Harris Teeter.

AUBREY: He’s actually having to turn customers away, which must say something about the taste of his tomatoes. Back at the kitchen of Firefly restaurant in D.C., chef Todd Wiss has been waiting to sink his teeth into one and the moment has come.

WISS: Wow. Amazing.

AUBREY: If we close our eyes, could you actually be convinced that maybe it’s July and this is an heirloom tomato right from your grandparents’ garden?

WISS: Without a doubt. Without a doubt.

AUBREY: Really?

WISS: Absolutely. I mean, it’s got the flavor, the smell, the texture, sweetness.

AUBREY: And Wiss says, he truly is surprised. Now, greenhouses like the one in West Virginia are starting to pop up on the outskirts of urban areas all over the country. So when you get that hankering for a taste of the summer, say maybe in mid-January, a good tomato might be closer than you thought. Allison Aubrey, NPR News. Transcript provided by NPR, Copyright National Public Radio.

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Experience with growing tomatoes in high tunnels: Insects, diseases and weeds

The crop many first-time high tunnel producers desire to grow is tomatoes, but for several reasons tomatoes may not be the easiest crop to produce in a tunnel system.

Posted on November 8, 2012 by Ron Goldy, Michigan State University Extension

High tunnels have made a big impact on production, especially for many small-scale vegetable producers. High tunnels have the potential of extending the season, improving yield and quality and making organic production possible for many crops, especially a crop like tomatoes that can be difficult to produce organically in our climate. This is the first of several reports on my observations from seven years of conducting high tunnel tomato trials at Michigan State University’s Southwest Michigan Research and Extension Center in Benton Harbor.

Insects, diseases and weeds

Reduction in pest pressure is one of the biggest potential advantages to tunnel production. The plastic covering is effective in keeping rain and dew off the leaves and fruit and this is extremely helpful in reducing disease. Many diseases require rain splash to move the pathogen from the ground into the plant and then move it within the plant. This splashing does not happen under a tunnel, except possibly on the edges. To germinate and grow, spores for many fungal diseases require wetting periods of several hours, which also does not occur in a high tunnel. Even if spores do land on the leaves the conditions are not conducive for germination. I have never seen a need to apply disease control measures on my tomatoes. This is significant, since field-grown tomatoes are susceptible to many destructive bacterial and fungal diseases.

Insects, however, are still a concern. The first year I grew tomatoes under tunnels they became infested with tomato hornworm. Since I was growing the tomatoes organically, I decided to wait for the parasitic braconid wasp (see image) to find and help control the hornworms. They didn’t show up and they never have over the past seven years. The clear plastic covering of the high tunnel filters out certain wavelengths of light that many insects use for navigation. This change in light quality may disrupt the navigation of insects like the braconid wasp.  However, daytime light levels and quality are not a concern to hornworms and other night-flying moths.

Tomato hornworm
Tomato hornworm parasitized by a braconid wasp.  Photo: R.J. Reynolds
Tobacco Company;

During the past seven years, tomato fruit worm, two-spotted spider mites and thrips have also been a yearly problem on tomatoes and tarnished plant bug and cucumber beetles have been observed on other crops. There are good organic and nonorganic controls for these pests. In Michigan, as long as the tunnel sides and ends are open it is considered an open system allowing growers to use products as if it were an open field situation.

Weeds continue to be a problem in a tunnel system. Raised, plastic-mulched beds can be established under the tunnels if growers have the proper equipment. Plastic mulch will control weeds in the row but weeds will still be a problem between rows even with limited water. Many herbicides for use in tomatoes require incorporation, an activity that may be difficult in a tunnel system. Therefore, the best way to control weeds between rows may be hand-hoeing.  Covering the soil with greenhouse ground cloth and planting through it, or placing containers on top of it, reduces weeds but they will still appear at the base of the plants.  Wind-borne seed will become established wherever there is bare soil.

For high tunnel research reports generated by Michigan State University Extension at the Southwest Michigan Research and Extension Center in Benton Harbor, Michigan go to and look at the Annual Reports starting in 2005.

For more information on commercial vegetable production, contact Ron Goldy at 269-944-1477 ext. 207.

This article was published by Michigan State University Extension. For more information, visit To contact an expert in your area, visit, or call 888-MSUE4MI (888-678-3464).

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Better climate with screen outside greenhouse

1 October 2012


Model calculations for greenhouse vegetable cultivation show that the use of a screen outside the greenhouse results in a better greenhouse climate than the use of a screen inside. The loss of production due to screening seems relatively small.

The research from Wageningen University (WUR) in the Netherlands shows that there might be some advantages as well, such as preventing photo-inhibition and water stress in the plant. The application of a screen outside the greenhouse to reduce irradiance peaks in greenhouse vegetables, is a new concept that deserves a further analysis.

In the cultivation of vegetables a high light transmission of the greenhouse is emphasised in order to uitilise the sunlight efficiently in the dark winter period. During sunny periods on summer days, the plants might be exposed to too high irradiance levels. In the case study of the WUR it was investigated whether these peaks in irradiance can affect the plant negatively and whether removal of these irradiance peaks by screens can lead to improvement of production and product quality. Possibly, this is a new step in the concept of the next generation cultivation.

The research was funded by the Product Board of Horticulture and the Dutch Ministry of Economic Affairs, Agriculture and Innovation and was carried out as part of the Innovation Programme Greenhouse as Energy Source.

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12 Tips On Choosing The Best Greenhouse Site

Consider several factors before determining the location of your greenhouse.

August 9, 2012

Строительство теплацSelecting a proper site for your greenhouse is just as important as selecting your construction materials, seeds, plant nutrients, and countless other components needed to ensure success. As many aspects should be considered when choosing a site, what follows are 12 factors to take into account before you make this important decision.

These site selection tips are from a presentation made by Pat Rorabaugh, a professor in the School of Plant Sciences/Controlled Environment Agriculture Center (CEAC) at the University of Arizona, at the Greenhouse Crop Production & Engineering Design Short Course that was held in Arizona in April.

1 Solar radiation: Since plants require light for photosynthesis, it’s critical to determine how the sunlight will reach them. Low light reduces photosynthesis and causes slow growth and fruit and flower abortion. The result is a low yield and minimal financial return. The location of your greenhouse and the time of year make a big difference in photosynthesis; locations that don’t receive enough solar radiation in the winter will need supplemental lighting.

2 Water: About 1 gallon of water mixed with nutrients is needed daily to supply each plant in addition to the water needed for evaporative cooling, which is about 10,000 to 15,000 gallons an acre each day. You can recycle nutrient water to increase your water use efficiency, but be wary of salt build-up. An initial water analysis should be done to assess salt and pH levels. pH levels should be adjusted to around 5.8  to 6.5 for tomatoes and if the source water is basic, as in more than 7 parts per million, add acids such as nitric, phosphoric, and sulfuric. If the source water is acidic, as in less than 7, add a base.

3 Elevation: Elevation affects high summer and low winter temperatures and will affect your cooling and heating costs, as well. For example, tomatoes function best between temperatures of 59°F to 86°F. If you happen to be at a higher altitude, here are several tips on how to control the temperature:

● Place plastic jugs of water around the plants when it’s cold. The water will garner heat during the day, and hold it during the night when the temperature drops.

● Place a temperature alarm in the greenhouse during colder months to alert you when the temperature drops. If necessary, you can place a ceramic heater in the house to increase temperature.

● If you have a rigid structure, use an automatic vent opener to control the heat, and if you have a soft structure greenhouse, you can open a flap to
permit heat reduction.

● During the summer use an automatic water system, possibly one that includes misters. During the winter disconnect all hoses to prevent pipes freezing up and water instead by hand.

4 Microclimate: There are many different factors that can affect your environment including latitude. Sea level at the poles will always be colder than sea level at the equator, and large bodies of water will heat up and cool down much slower than land masses. For example, San Diego, which is next to the Pacific Ocean, has much smaller fluctuations between day and night temperature than does the Sonoran desert, which is not close to a large body of water and whose temperatures can fluctuate.

Take trees, mountains, and other obstructions that could possibly cast a shadow on the greenhouse into consideration, especially in the morning. Mountains also have the ability to affect wind and storm patterns. Other environmental considerations include: clouds and fog, which can gather at certain times of the day in specific areas and reduce sunlight and photosynthesis; high wind that can cause structural damage and suck heat away from the greenhouse; blowing dust and sand which can braze the greenhouse glazing; and lastly, snow.

5 Pest pressure: Make sure to either choose a site that is far away from other agricultural production areas, or create a buffer zone between your operation and other production areas to prevent pest infestation.

6 Level and stable ground: Be aware of the stability of the ground on which you construct your greenhouse; it should not be subject to shifting. The ground must also be graded for water draining (a 6 inch drop in 100 feet). Additionally, the ground must be compacted so that it won’t begin to settle after the greenhouse is built.

7 Utilities: Make sure that you have the following utilities at your disposal:

● Telephone service

● Three-phase electricity

● Fuel for heating/CO2 generation: natural gas, propane, fuel oil, electricity. Alternatives include solar, compost, woodchips, nut hulls, etc.

8 Roads: Access to good roads is a must. For example, if roads are unpaved, when you transport your harvest, the fruit will be subject to all of the rocky movement of the vehicle which could lead to bruising, crushing, and other major damages for your fruit.

9 North-South orientation: The greenhouse as well as the plants inside the greenhouse should be oriented north-south, especially in southern latitudes to maximize the amount of light that enters, and to create the best ventilation possible.

10 Capability of expansion: It’s advisable to purchase more land than you initially need so that you have the possibility of expanding later.

11 Availability of labor: The owner or manager of the operation will need two different types of labor forces:

● Trainable laborers as a retainable workforce. These laborers will take care of the plant and fruit harvesting and packing.

● Specialty laborers. This includes growers, plant production managers, plant nutrition specialists, plant protection specialists, office/computer specialists, labor/management specialists, and marketing specialists.

12 Management Residence: Growers and managers should all live relatively close to the greenhouse in the event of an emergency.

Alexander is the Content Editor for Productores de Hortalizas, a Meister Media Worldwide publication

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Welcome to our new website!

Logo agrispanWe would like to welcome you to our new site:! With this site we provide information for commercial growers around the world. Besides our offering of several types of greenhouses, we will also support customers by giving tips and advice for professional greenhouse growers.

Over the coming month we will be adding new features and content to the site. So keep checking back to see what’s new.  If you have problems viewing the site or any questions or suggestions about what you’d like to see, let us know by leaving a comment below.

We hope that you find our new blog and website helpful and informative, and we really look forward to hearing your thoughts!

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