January 2007

Lessons Learned: Polycarbonate Replaces Whitewashing By Meghan Boyer

Shading plants from the sun and heat is necessary for many growers, but especially for those who grow in warmer, Southern climates like Blanco, Texas. Jimmy Klepac, owner of Klepac Green-houses, Inc., grows potted flowering crops using a whitewash shading compound in conjunction with shade curtains to protect the plants from the Texas heat. While the compound works well to shade plants, it takes more time and labor to maintain than Klepac wants. Additionally, Klepac says the results are not as consistent as he would like, which is why he considered alternate methods of lowering heat and light for his new greenhouse build.

Using A Shading Compound

Klepac found that in a demanding climate such as his, shading compounds need to be applied frequently throughout the growing season to be most effective. "In the spring you put on a white coat," he explained. "Then once a month you put on another coat to knock the summer heat out because it gets so hot here in Texas." In the fall, workers have to use brooms and hoses to wash the compound away so crops can get more sun during the winter.

The amount of labor needed to maintain the shading compound is frustrating for Klepac. The process can be quite time consuming for his workers: "You go up there and spray it, and everything's good for a few weeks, maybe a month. Then it gets hotter, or if you get some rain, maybe it washes some off, and you need to go back and reapply," he explained. More important than the amount of time whitewashing takes, Klepac says that sending workers onto the greenhouse roof to apply and remove the compound can be dangerous; the whole process increases the possibility of worker injury. "We haven't had anybody fall, but it is still hazardous," he said.

The shading compound has an effect on his business as well. Inconsistent crop quality is a problem he has noticed in his whitewashed houses. At times, too much heat and light can come in through the shading compound, which can impact Klepac's crops. "[The shading compound] has an effect on the crop quality overall," he said. "When you whitewash, it's not really uniform because you have a few weeks when the temperature and the light is just right, then all of a sudden it starts getting hotter, and you start to see some crop deterioration, and you have to whitewash again."

New Structure, New Covering

Last summer, Klepac built a new greenhouse with an 18-ft. gutter height to bring in more light and create a higher buffer zone between the crops and the summer heat. With labor and crop consistency concerns on his mind, Klepac chose a polycarbonate covering for the house. The new covering, DynaGlas SolarSoft, is supposed to diffuse light better than his old covering. He hoped the new covering in conjunction with a 55-percent shade fabric would prevent him from having to use a shading compound on the new house.

DynaGlas SolarSoft polycarbonate technology from Palram Americas is designed to diffuse light that is transmitted through the sheet while letting a high level of PAR light through. Direct radiation of infrared light should be removed, which can reduce leaf temperature and plant burning. Different types of DynaGlas and SolarSoft are available; light transmission properties range from 45 to 92 percent depending on the type of DynaGlas and Pigmentation chosen. Klepac chose DynaGlas SolarSoft 85, which is designed to deliver 85-percent PAR light transmission and 100-percent diffusion, for his new greenhouse.

Seeing The Effects

The DynaGlas SolarSoft covering works for Klepac, and as he hoped, he has not had to whitewash his new greenhouse. "We've had no whitewash up there. We just pull the shade in late morning when it starts to get hot. Then late in the afternoon after the sun starts to go down, we open up the shade to let the light back in," he explained.

Not having to apply shading compound to his new greenhouse has saved Klepac time and money: He saves money because he does not need to purchase shading compound for the new range. Additionally, he does not need to allocate time and labor to applying and maintaining whitewash, which amounts to additional savings.

Klepac also found the new polycarbonate affects the way he grows in his new greenhouse. He has not experienced high light levels in the new structure, which has allowed him to decrease the strength of the PGRs he uses on pot mums.

And while he experienced heat delays, sometimes up to two weeks, with his pot mums when growing with the shading compound, he has not had any such delays with the DynaGlas SolarSoft covering. "[The DynaGlas SolarSoft] has helped us get our crops to market on time, which is a great benefit," said Klepac. "It has been easier to schedule. A lot of times when you get heat delay and a customer asks for a big order, you're not sure if you can get it to them on time, but this year [the covering] has helped us get to market more consistently."

DynaGlas SolarSoft 85 works well for Klepac because he grows in the South, and the covering lets the right amount of light through. Klepac recommends that other growers who are looking at new greenhouse coverings choose the right coverings for their locations; a different covering can change the way growers go about shading their crops.