LED Horticultural Grow Lights Make Propagation Easier and Faster

Rooting cuttings in separate propagation room cuts a week off of production schedule

 

by David Kuack and Jean-Marc Versolato

 

Minnesota in the winter is not the ideal place to try to propagate woody ornamental cuttings. Cold temperatures and low light conditions make rooting cuttings a real challenge. So when Jean-Marc Versolato at Bailey Nurseries in St. Paul, began reading about how European growers were using LED lights to root cuttings it piqued his interest.

Versolato, who is the company’s IPM manager for the greenhouses, worked with Philips Horticultural Lighting and Hort Americas to design a separate propagation room not in the greenhouses to trial the LED lights.

“I felt that the LED lights were going to be the next improvement in growing,” Versolato said. “We started in February 2011 and ran a variety of crops under the lights. We used three Cannon carts tied together side-by-side to form one large shelf that can hold up to 15 trays. The trial was conducted in a corner of our germination room.”

Versolato said the germination room was the perfect location for the trial. Located inside a production building, the room provides a constant 70°F and is equipped with fogging nozzles in the ceiling. The trial propagation area was partitioned with black plastic to avoid light contamination from the room’s fluorescent lights.

The cuttings only received red and blue light from Philips GreenPower LED production modules. The 5-foot modules, which matched the size of the carts, were located about 16 inches away from the cuttings.

Cuttings were taken from a variety of plants in the greenhouses, including Spirea, Celastrus, Physocarpus and Hydrangea. The cuttings were sprayed with indole-3-butyric acid (IBA) to help initiate rooting. The cuttings were stuck in 38-cell plastic trays (standard 11- x 21-inch) containing Preforma rooting plugs. The cart shelves held five flats of each genus for a total of 15 flats.

The fogging nozzles filled the entire room with fog. There cuttings received no direct water misting or spraying.

“By using the fog we eliminated droplets from forming on the foliage, which greatly reduced the chance for Botrytis and loss of cuttings,” Versolato said. “Gravity caused the fog to descend on the cuttings and the fog kept the cuttings turgid.

“The LED lights generate heat, but nothing like other lights available for growing. For this reason the Preforma plugs remained moist and we didn’t need to apply any additional water.”

The cuttings rooted in three to four weeks. Versolato said in the greenhouses the cuttings root in four to five weeks and occasionally take longer for some species.

 

Crops on Cannon carts under fog and Philips LED Grow Lights

Trialing other crops

After the initial propagation trial proved successful, Versolato was looking to try additional crops. During the summer the company purchased tissue-cultured lilac micro-cuttings.

“We rooted three flats of micro-cuttings under the LED lights in three weeks,” Versolato said. “They required very little grower care whatsoever. The environment in the propagation chamber was controlled by the LED lights and the fogging nozzles. Also, no fungicide spray applications were made.”

Versolato said winter cutting propagation in the greenhouse can be difficult to manage because of low light levels, the temperature and the humidity. Based on the successful results of the lilac trial, Versolato said the company plans to root 25 percent of its French lilacs (Syringa vulagris) cuttings in the propagation room.

“In January and February we will begin to root the micro-cuttings lilacs in the room,” he said. “We are probably going to root six to seven varieties, putting a sample of each one of them under the LED lights to see how they perform. We’re going to do six carts with three shelves each. Each shelf holds five trays, for a total of 90 flats under the LED lights. This trial will be our first multi-layer production attempt.”

Although pleased with the rooting results under LED lights that he has gotten so far, Versolato said he thinks there are other factors that are instrumental in the cuttings rooting faster.

“The cuttings are being rooted in the Preforma plugs instead of greenhouse growing media,” he said. “The chamber also has very good temperature and humidity control. All of these factors put together help to shave seven days off of the rooting schedule.”

Expanding propagation

Versolato said the propagation room will be used for hard to root crops. The room can hold 40-50 carts.

“We are not going to be wasting space in the trial area for crops that are easy to root in the greenhouses,” he said. “We are looking at a list of a dozen varieties/species that we would root in the room knowing that they are difficult to root in the greenhouses. Some of the plants that will be trialed include Rhus typhina ‘Bailtiger’ Tiger Eyes, Amelanchier and Betula.”

For the lilac trial, 15 flats of cuttings were lit by five modules of LED lights.

“We wanted to be sure that we had enough light for all of the flats,” Versolato said. “For this coming year the lights are not going to be directly above the plants or mounted on the carts. We want to be able to move the carts in and out of the propagation room.”

The lights will be mounted on a bracket shelving system and located about 16 inches above and to the side of the cuttings. Versolato said this will make switching and handling carts a lot faster and easier.

 

The right recipe

Versolato said the red and blue LED lights come in different recipes depending on what a grower wants the plants to do, whether it’s develop roots, hasten flower initiation or speed up time to flower.

“The recipe that we are using is generic and works with just about any plant we are trying to propagate,” he said. “It would be too difficult to have a different recipe for every genus and species that we are growing.”

Versolato said Philips can provide growers with the information to tweak the light wavelength recipe to increase or decrease the amount of red light or blue light.

“For Dutch growers, who may be producing acres of Anthurium or another mono crop, it is easy for them to have a specific light recipe for that one crop,” he said. “But in our situation where we have many different crops, it would take a lot to come up with a different recipe for each one of them.”

Finished crop on Cannon carts (multilayer production)
under LED grow lights

Finishing plants

Versolato is also planning to do another trial finishing plants in the greenhouse under LED lights.

“Philips has different types of LED lights,” he said. “In addition to the light modules we used for propagation, Philips also has flowering light bulbs that can be screwed into regular light fixtures. One helps to promote flowering.

Versolato is planning to do a small trial with the flowering LED lights to see if they help with flower bud initiation on impatiens during early season crop production. He said the first impatiens crop is grown during the short dark days of the year and the plants are very slow to develop buds.

Even though the first crop is currently grown under high intensity discharge lights, Versolato wants to see what impact the addition of LED lights will have on the plants.

“We want to try some LED bulbs mixed in with the HID to see if they help to improve bud count,” he said. “The crop would be put out in the greenhouses around Feb. 23. The light level in the greenhouses in Minnesota during February is very low. We’re planning to trial about three benches with the LED lights.”

For more: Bailey Nurseries Inc., www.baileynurseries.com. Hort Americas, www.hortamericas.com. Philips Horticultural Lighting, www.philips.com/horti

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com. Jean-Marc Versolato is IPM manager, Bailey Nurseries in St. Paul, Minn.
 

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