Light bulb moment

Sierra Gold Nurseries in Yuba City, Calif., grows more than a million nut and fruit trees a year. The company’s primary market is growers in California, Washington and Oregon.

“We currently do more bare root trees than what we do in containers,” said Cliff Beumel, Sierra Gold’s director of product development. “We are targeting to have a nursery where we grow half the trees as bare root and half in containers.

“Looking long term at the California nursery industry, more of the production will be done in containers and less as bare root. Mounting regulatory issues related to ground water and the inability to fumigate the soil are causing more production to be done in containers. Growing in containers is more efficient because plants can be grown in greenhouses and multiple crops can be produced. The natural cycle of bare root trees only allows us to grow one crop per year.”

Beumel said that seven years ago the nursery was 100 percent bare root. During the last three years the company has doubled its containerized production every year. Beumel said the company is positioning itself to increase its ability to meet the needs of its customer base.
 

Increasing use of tissue culture

This summer Sierra Gold opened a 10,000-square-foot tissue culture lab to produce nut and fruit tree rootstocks.

“Virtually all of the trees that we produce consist of a scion cultivar put onto a rootstock,” Beumel said. “A rootstock is chosen for its attributes for a given area along with the desired cultivar, whether it’s a nut or fruit variety. Most of the trees are produced as 1-year old trees.

“For over 10 years we had been purchasing tissue culture propagated rootstock from suppliers. Our orders were increasing and we saw new rootstocks on the horizon which were going to push half of our propagation material to be tissue cultured. We made the decision to start our own tissue culture lab primarily for internal use only. However, it is possible down the road that we will generate supplemental income by supplying the industry with rootstocks.”
 

More uniform, faster growth

Before determining the type of lights to install in the company’s tissue culture lab, Beumel said a lot of information was gathered from other labs, researchers and consultants from around the world.

“We became aware of what the options were and it was a simple cost analysis of LEDs vs. fluorescent lights,” he said. “We were so confident in our decision of choosing LEDs that we never trialed LEDs against fluorescent lights. We had collected enough evidence that LEDs were superior to fluorescents. We did trial different LEDs against each other. We only needed to decide what LEDs we were going to use. We were fortunate that the LEDs were financially viable at the time our lab was being built.”

Sierra Gold worked with Hort Americas to select the Philips GreenPower LED Production Module Deep Red/Blue 120 for the lab.

“In tissue culture, uniformity is very important where everything is like a factory,” Beumel said. “This is difficult to achieve with plants, but the closer you can get to it the better. Uniformity of plants under LEDs is better across the lab than under fluorescents.”

Beumel said another critical factor for success with a tissue culture lab is multiplication rates. “There are two parts to the multiplication equation,” he said.

“There is the number of plantlets that are produced from each multiplication cycle and there is how quickly these cycles occur. We believe because the LEDs deliver more usable light in the grow room that the plant proliferation rates should improve due to either greater uniformity or enhanced plant growth.”
 

Fewer lights, lower energy use

Beumel said even if LEDs only operated equally to fluorescent lights in terms of plant growth, the energy savings alone provided by the LEDs convinced him they were the right choice for the lab. Beumel said the fact that the payback was only a few years made the decision that much easier.

“We are using one 35-watt LED module instead of two 40-watt fluorescent bulbs,” he said. “The LEDs use about 43 percent as much energy as the fluorescent lights, which is a major factor considering the high energy rates we are paying in California.”

Another energy-related factor that influenced Beumel’s decision to install LEDs is the amount of heat given off by the lights.

“In a tissue culture growth room the plants have to be kept at the right temperature,” he said. “You’re heating and cooling, but mostly cooling. With fluorescents you’re putting heat into the room.

“A temperature increase of only 5°F can have an adverse effect on the plants. If plants grow too fast, vitrification can occur. The plants grow so fast that they can’t sustain themselves and plant quality suffers tremendously. This can occur when there is a slight change in temperature.”

Beumel said if a fluorescent ballast with two 40-watt bulbs is sitting underneath a tissue culture shelf the temperature of the shelf above the lights is going to be warmer.

“You can put your hand on the shelf and feel it is warmer. People using fluorescents need to make sure there is enough air space between the lights because of the heat they generate. The warmer temperature can lead to problems with uniformity if the plants are not spaced out. The closer the shelves can be spaced together means more shelves enabling us to put more plants in the lab. With LEDs we can put in more shelves and grow more plants making it a more efficient set up.”

Beumel said before the company made the decision about which lights to install he talked with operators of tissue culture labs to confirm his company’s findings about LEDs.

“The LEDs should last 50,000 hours, plant performance is better under the LEDs, there is a major energy savings difference and the payback is a few years. It was a no brainer for us as to which lights to install.”

For more: www.sierragoldtrees.com; www.hortamericas.com

Photos courtesy of Sierra Gold Nurseries

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.