Purdue University researchers’ success in using red and blue LEDs as the only source of light to grow ornamental plant seedlings indoors has led to a new phase of determining whether they can reduce production time with more colors.
The research is important because most seedlings are grown in greenhouses in the late winter and early spring, a time when sunlight with enough growing power is low, especially in northern states. Seedlings need to grow at that time to meet spring and summer sales of bedding plants, so supplemental lighting from electric lamps is typically needed.
In the first part of the research, associate professor of horticulture Roberto Lopez and master’s student Wesley Randall grew seedlings from five bedding plant species – impatiens, marigold, petunia, vinca and zonal geranium – some using light-emitting diodes, known as LEDs, as a supplement to sunlight. They found that the quality of seedlings grown with LEDs was similar to – and in some cases better than – those grown in a greenhouse with high-pressure sodium lamps (similar to street or arena lamps) to supplement sunlight.
They then decided to see if the seedlings could be produced indoors with LEDs as the sole source of light.
“It was quite surprising to see how uniform, compact and sturdy the seedlings were compared to seedlings produced in the greenhouse with sunlight and supplemental lighting from LEDs,” Lopez said. Compact seedlings are desirable because tall seedlings can be damaged in boxes during shipping. I didn’t think we could produce such a nice, high-quality plant without the sun,” he said.
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