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High energy efficiency, lower costs

Shades of Success

PLEXIGLAS? greenhouses bring out plants' true colors 

Begonias are prized for their eye-catching, vivid hues - vibrant red, sunny yellow or neon pink. In South America, where they originally come from, they are perennials that grow outdoors, with no glass to separate them from UV light. The pigments in their leaves and blossoms ensure their natural radiance. But similar effects can be achieved in the greenhouses of Central Europe too. "In our greenhouse made of PLEXIGLAS ALLTOP?, the begonias grow under the same conditions as outdoors," says market gardener Karl Zwermann from Usingen in the Hochtaunus region of Germany. And he should know, because he was able to make a direct comparison after adding a PLEXIGLAS? greenhouse to his existing glass structure over 30 years ago. Karl Zwermann offered plants from both greenhouses on the wholesale market. "But soon, customers only wanted the begonias from the PLEXIGLAS? greenhouse. It wasn't just because of the colors - the plants were more compact too," says Mr. Zwermann, who has observed similar effects in poinsettias as well. This is also thanks to the material's high UV transmission of around 91 percent.

PLEXIGLAS? for a special climate

When Karl Zwermann chose a PLEXIGLAS? greenhouse over thirty years ago, he was a real pioneer. Plant growers came to visit him from as far off as Japan to see his greenhouse for themselves. "We created a very special climate for our plants beneath the PLEXIGLAS? sheets," Mr. Zwermann tells us. Air circulation between the plant rows made sure the plants had warm feet, but a cool head. The crucial factor was the material's good heat insulation. Unlike the glass greenhouse, with its inferior insulation properties, the plants did not suffer from the cold, and the temperature remained constant. "That alone saved us 35 to 40 percent in energy," Mr. Zwermann sums up. "With modern technology, we save over 50 percent." What was highly topical back in the days of the oil crisis and rocketing prices remains every bit as important now that we are faced with the challenges of climate change.

More light for faster growth

Skeptics back then told Mr. Zwermann it was impossible to grow plants under PLEXIGLAS? sheets. But his results spoke for themselves. Not only did he succeed in obtaining brighter colors and cutting energy consumption, his plants rewarded him with denser and more attractive growth. The diffuse light transmitted by the PLEXIGLAS? sheets protects the plants from burning. "That means I could let in all the light for longer stretches at a time and didn't need to shade the begonias from direct sun," Mr. Zwermann explains. And the plants never had to strain upwards to get enough light. With plenty of natural UV radiation, the plants grew bushy and strong, with hardly any need for growth inhibitors, and within shorter cultivation times. So the 1,300-square-meter greenhouse built in 1972 was continuously expanded. Mr. Zwermann added to his premises until he finally had a cultivation area of 8,000 square meters for his begonias. Despite having retired in 2005, he still visits his former premises now and then to enjoy the splendid sight of the brilliantly colored begonias and poinsettias growing below PLEXIGLAS?.  

 


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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