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Bergen’s Greenhouses: Cutting-edge technology

When you enter Bergen’s Greenhouses in Forest Lake, Minnesota you hear a faint humming noise that starts and stops, and starts all over again. And if you sense the ceiling above you is moving, in a way it is. Long rows of potted plants are suspended from the roof trusses in hanging containers. These columns of green are on the move all day long, only stopping to be watered or harvested. It is an impressive sight to look along the 1100 feet expanse to the end of the building. 117,000 hanging pots of petunias and impatiens sway gently as they move round the greenhouse from north to south – 400,000 hanging plants leave the greenhouse every year.

This "moving" canopy conceals a trove of technology. A motor drives the rows of plants and stops them at predetermined times. The workers who harvest the plants drive along the rows with lift trucks and take off the plants that are ready for transport. "We have a unique system," says Managing Director Kevin Johnson. "Not only do we make better use of our greenhouse space, we also simplify our work processes." Workers no longer need to bend over to pick the plants, and there is no need for watering by hand. And the plants flourish because they get more light in the upper section of the greenhouse.

The family business in Minnesota has now been operating for four generations. They were one of the first company in North America to build a greenhouse with PLEXIGLAS ALLTOP? double-skinned acrylic glazing and thus to appreciate Evonik Cyro’s 30 year non-yellowing warranty.  . "Locally Grown since 1921" is Bergen's slogan for selling mainly potted plants like hydrangeas, lilies, geraniums, impatiens, begonias and petunias. The company is also renown for seasonal plants like  Easter Lilies and poinsettias, which are bought largely by retailers like Wal-Mart, Lowe’s, Target and to a smaller extent by big, independent florists in Minnesota, North Dakota, South Dakota, Iowa, and Wisconsin. With four sites and some 1,130,000 square feet of cultivation surface, Bergen’s is one of the biggest growing enterprises in the region, and at the same time is at the cutting edge of technology.

In addition to the system of the hanging containers, Bergen’s has installed another innovative technology.  Built with a unique cutting-edge design, the convertible-style roof opens and closes.  The option to open and close the roof completely, allows a simple control of the greenhouse’s climate by venting air that is either too humid or too dry without the use of expensive, energy driven electric exhaust fans. It also enables the plants to grow under natural conditions and become hardened to the climate conditions they will be exposed to when sold.

After gazing overhead, it's worth looking back down to the floor. It gets wet and dries again at the flick of a button. The potted plants stand in trays that are just a few inches high. When they need water, the trays are flooded. The tanks beneath the floor contain over a million liters of water. The water also contains the right amount of fertilizer that is calculated by computer. This has other advantages beside the precise dosage and the reduced need for manual work: "The water that runs off with the fertilizer can be used again, and we also have far less plant disease and quality losses because there is no water dripping onto the plants," Kevin Johnson explains. Bergen’s in Forest Lake also relies on quick and simple handling of cuttings too. "Previously, we used to  transplant the cuttings and then load them onto big trucks. Workers then took them to a certain area of the greenhouse where they were watered by hand," Johnson says. Today everything is much easier: The cuttings are planted and automatically loaded onto an aluminum transport system. After a tour through the irrigation unit, they are automatically conveyed to their final destination in the greenhouse, where an overhead crane or stacker lifts the pallets into the growing beds.

The entire technology at Bergen’s Greenhouses is based on product quaility  "To maintain our market position, we have to offer first-class goods. We have to meet the standard we are known for in this region or lose our advantage," “Costs play a major role. We avoid costs by saving energy” Johnson says.  PLEXIGLAS? is a big help in that respect. At the Forest Lake site, all 475,000 square feet of greenhouse space have been glazed with energy efficient PLEXIGLAS ALLTOP? Double Skinned Sheet. This part of the country is often subject to sub zero temperatures and from November to April there is always the chance of heavy snowfall. The heat-insulating glazing has proved to be a real cost factor in this climate. "We use half as much energy as we would with glass," the Bergen’s have calculated. And PLEXIGLAS? offers further benefits compared with glass and other materials in terms of light yield. "The material's 86 percent light transmission means the plants grow faster, are more colorful and more resistant to disease. We can compare them directly with plants from our greenhouses built with other materials," 

Following the success of Bergen’s first PLEXIGLAS? greenhouse in 1978, they continued to build greenhouses by the acres - 2 acres in 2003, 2 acres in 2004, 4 acres in 2005, 1 acre in 2006 and 1 in 2007.  “The next PLEXIGLAS? greenhouse is already being built.” confides Johnson.  Rows of potted plants will soon revolve there too. And the begonias and petunias will probably attract other visitors as well. If faint chirps can be heard above the low hum of the conveyor belts, the staff knows they have to take a closer look, and relocate the bird that has built its nest again in one of the flowering containers. 


The story about the queen of pot plants is just one of the articles in the current issue of the Greenhouse Journal: PROFITABLE GROWTH UNDER ACRYLIC. Download PDF  

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