Can you use LEDs in all production phases of controlled environment agriculture?

Shenandoah Growers uses LEDs in all stages of its organic potted herb production, including propagation, finishing and postharvest.

by David Kuack

Shenandoah Growers in Harrisonburg, Va., began operating in 1989 as a small company producing culinary herbs in greenhouses and outdoors in the field. In 2007 the company built its first state-of-the-art glass greenhouses to produce organic potted culinary herbs. Today Shenandoah Growers has about 6 acres of greenhouses and grow rooms at its Virginia headquarters. It also has satellite controlled environment agriculture operations in Georgia, Indiana, Michigan, Texas and Washington.

The company has replaced its poly-covered greenhouses in Virginia with Venlo glass greenhouses equipped with energy curtains, grow lights, a moving gutter system and ebb-and-flood benches. An increasing amount of automation was installed when the company began growing herb plugs in 2007.

“The layout in our Virginia operation is completely different than the original facility,” said Bob Hoffman, who is chief science officer. “Originally the layout was geared to fresh cut herbs, now it is primarily certified organic potted herbs. With the Venlo greenhouses and the automation that was incorporated we were able to double our output of potted herbs.

“Combining all of our controlled environment facilities nationwide there is about 8 acres of total greenhouse and grow room production. We also have a few hundred acres of field production, all of which is certified organic. We are doing some leafy greens in those facilities as well and expanding that production. We have done trials with leafy greens over the years. Now we just need more production space to do it on a larger scale. Almost all of the controlled environment agriculture production is certified organic. We also do some hydroponic basil in our Washington and Texas locations.”

The company’s herbs are sold to supermarket chains nationwide. It produces about a dozen different potted herbs and about 25 different fresh cut herbs. 

Incorporating LEDs into all growth stages

When Shenandoah Growers initially began to replace its old greenhouses it installed high pressure sodium (HPS) lamps in its new greenhouses. In 2012 the company began trialing LEDs for its plug production.

Bob Hoffman, chief science officer at Shenandoah Growers, said LEDs have enabled his company to produce more turns per year in the same production space.

“We began looking at the LEDs to try to improve the quality of the young plants that were going into the greenhouses,” Hoffman said. “This is usually a very sensitive stage. If there were cloudy days followed by bright sunny days there were losses in plug production. Just as the plugs were entering the final stage of germination they were very tender young seedlings. Events would occur hampering production that would affect the plants five to six weeks later when they were entering final production. The incentive for us to install LEDs was to solve problems and to increase productivity in a controlled environment.

“We started using LEDs in our young plant production. LEDs were initially used at the plug stage where we have the highest density of plants. This provides us with our quickest return on investment. The plugs go through our automatic transplanters where they are planted into pots and then placed onto grow carts. At this time the plants go into a grow room, also equipped with LEDs, where they are pot tight before being spaced out into our final growing system. The plants are then planted in the greenhouse growing systems. After growing to their final size in the greenhouses, the plants are harvested, packed and shipped out.”

Hoffman said it is most cost effective for the company to use LEDs when the plants are in the plug stage and when they are pot tight. In its propagation greenhouse overhead LED top lighting is also being used to root cuttings of rosemary and mint.

Shenandoah Growers initially used LEDs for plug production where it has its highest density of plants. This provided the company with the quickest return on investment.

“Sometimes the finished potted herbs go into a grow room equipped with LEDs before they are shipped to our retail supermarket customers,” he said. “During this postharvest stage the LEDs are being used to improve the quality of the plants. The light spectra provided by the LEDs can enhance both the flavor of the herbs as well improve the antioxidant, flavonoid and carotenoid levels, increasing the overall nutritional content. The LEDs also tone the plants and improve their overall color which gives them better eye appeal.

“This LED postharvest treatment is being done on a small scale right now. Eventually we would like to do the LED postharvest treatment with all our plants.”

The company is also growing microgreens and leafy greens under LEDs.

“We are growing a small amount of leafy greens under LEDs, but we are looking at potentially expanding that production,” Hoffman said. “We are always looking at new crops and new varieties. Growers always want to do trials first to make sure they can grow a quality crop.”

Shenandoah Growers is planning to increase the use of LEDs at its other satellite production facilities.

“Some of these facilities currently don’t have any supplemental lighting,” Hoffman said. “Some do have supplemental lighting and some will have LEDs installed in new production facilities that will be added.”

Not all LEDs are the same

Hoffman said when his company began trialing LEDs it didn’t take long to find out not all LEDs are the same.

“There is quite a substantial difference between brands, set ups, intensities and spectra,” he said. “We began by identifying the ones that worked well for us. We had to determine how the lights could be incorporated into the production systems that were cost effective for us. Then we had to identify how we could save labor steps by incorporating these systems. We looked at the LEDs initially to solve problems and to make our production much more efficient.”

Shenandoah Growers is replacing high pressure sodium lamps with LEDs, which provide double the light output of the HPS lamps.

Although Shenandoah Growers still has some of the original HPS lamps it installed in its Virginia operation, as these fixtures are replaced LEDs are the replacement of choice.

“LEDs have lowered our energy costs and we are producing more light energy for the same amount of electrical cost,” Hoffman said. “When we replaced the old magnetic ballast HPS with LEDs, we were able to get double the light output. That has enabled us to produce more turns per year in the same production space. We could have installed the LEDs and tried to save dollars of electrical cost, but we have been able to get more production out of the same space without having to build additional greenhouses or growing facility space. Also, length of the plant internodes is shorter so there is less stretch, improving the predictability of the crops.”

Criteria for choosing LEDs

Hoffman said growers interested in installing LEDs should do their research before making their choice of lamps.

“Speak with other growers who have installed LEDs and talk with the researchers who are working with LEDs,” he said. “Once growers have narrowed down their choice of LEDs, bring in samples of the lamps and try them out on a small scale. Make sure it is a good honest trial and see what kinds of results occur.

“Growers should determine the efficiency of the lights in converting electrical energy to photons and whether the light spectra produced by the lamps are best for the crops being produced. Then determine the best quality lamps for the best value financially.”

Shenandoah Growers found the light spectra provided by LEDs have eliminated the stretching of plant internodes that occurred with HPS lamps.

Hoffman said growers should also find out what type of guarantee or warranty the manufacturers provide for the lamps.

“The warranty should be a minimum three-year, bumper-to-bumper replacement guarantee and preferably a five-year guarantee,” he said.

For more: Shenandoah Growers, (540) 896-6615;

Editor’s note: If you are interested in learning more about how Shenandoah Growers is using LEDs, plan on attending the 1st GLASE meeting on Nov. 5, 2018, in Ithaca, N.Y. Chief science officer Bob Hoffman will be one of the growers speaking at the event.

David Kuack is a freelance technical writer in Fort Worth, Texas;