Tomatoes grown around LED lights in the winter can significantly reduce greenhouse energy costs without sacrificing yield, according to a Purdue University study.

Mitchell and doctoral student Celina Gómez experimented with light-emitting diodes, which are cooler and require far less energy than traditional high-pressure sodium lamps used in greenhouses. They got the same yield — size and number of fruit — with high-pressure sodium lamps and LED towers, but the LEDs used about 25 percent of the energy of traditional lamps.

The scientists think the method could have other advantages because the cooler LEDs can be placed much closer and along the sides of plants, lighting not only the top, but also the understory.

"The leaves are photosynthesizing on the lower parts of the plants, and that may be helping with the plant's energy," Gómez said. "We're getting the high intensity of the LEDs close to the plants because they're not hot like a high-pressure sodium lamp. If you put one of those close to the plants, you'd scorch it."

The heat from high-pressure sodium lamps account for about 15 percent to 25 percent of the heat needed to warm greenhouses, but Mitchell said that's inefficient."That's a very expensive way to heat a greenhouse, through lighting," Mitchell said.

Mitchell said the goal of his research is to reduce prices to the point where local growers could compete with the prices of tomatoes that are shipped from faraway places. Local tomatoes would be harvested vine ripe, would taste better and would boost local economies.