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Breeding crops for controlled environment production

Controlled environment agriculture growers have been trying to fit a square peg into a round hole by growing field crops in indoor environments. This is changing as research tries to match plant genetics with the production environment.

During this year’s International Congress on Controlled Environment Agriculture (ICCEA) in Panama City, Panama, University of Florida horticulture professor and keynote speaker Kevin Folta discussed the overlooked reality that food crop varieties have not been bred for indoor controlled environment production.

“One of the limitations of controlled environment agriculture (CEA) is that the conditions do not match the genetics,” Folta said. “Plants being grown in CEA environments were actually developed for field production. There are a lot of opportunities that go unrealized by growing plants in a controlled environment. It’s like asking Chihuahuas to pull a dog sled. Plants that were bred for one application are expected to perform under very different applications. The genetics don’t match.”

Research has begun to develop the next generation of plants with the potential to develop different products using the same set of genetics by changing the environment.

Creating the next generation of plants

Folta said research has begun to develop the next generation of plants with the potential to develop different products using the same set of genetics by changing the environment.

“By flipping a switch and varying the light spectrum we could change green leaves to purple or have the plants accumulate specific flavors or textures or nutraceutical compounds,” he said. “That is all very realistic. This is like being able to shine a different light spectrum on a Chihuahua and turning it into an Alaskan malamute or a dachshund. A plant’s body, its composition, its chemicals, its secondary metabolites could be altered by changing the light environment. We need plants that are ready to do that. We need to identify or create those genetics.

“We are exposing plants to different light spectra and evaluating how the plants behave and perform. Then we will work with plant breeders to develop the next varieties.”

Varying the light spectrum has the potential to change leaf colors and textures and to have plants accumulate specific flavors or nutraceutical compounds.
Photos courtesy of Kevin Folta, University of Florida

Need for more industry involvement

Folta said the companies that are developing and manufacturing the lights for CEA production should become more involved with the development of plants grown in these environments.

“The lighting companies should be working with the university researchers and plant breeders,” he said. “The lighting companies should be financing the development of proprietary varieties. Unfortunately that hasn’t been an area of interest for the lighting companies. They want to make and sell lights. They forget the seed. The seed is a much more complicated machine.

“The lighting companies should be able to say to the growers here are the grow lights we are offering and here are the seeds that grow best under them. That opens up recurring revenue for the lighting companies. It behooves the lighting companies to focus on identifying plants that perform best with their products. It’s like saying that a Ford engine does best with a Motorcraft oil filter. It’s manufacturer’s optimized matching parts.”

Folta said plants are the most complicated part of matching the genetics with the environment and the part that people worry least about.

“It doesn’t matter whether the breeding company or the lighting company takes the initiative to develop the genetics,” he said. “This is going to happen whether it’s private plant breeders, universities or technology companies. This is another niche to create new genetics. You’ll see people filling this void.”

Researchers are learning that green, far red and UV light have important roles to play in controlled environment agriculture plant production.

Limiting, changing the production environment

Even technology companies like Panasonic, Toshiba and Fujitsu are finding opportunities in controlled environment agriculture.

“These types of companies will develop the genetics or will find the genetics that work well in CEA environments,” Folta said. “For now the field genetics will continue to be put in artificial conditions and the indoor environment will be reshaped to accommodate the plants. What should be done is finding or developing plants for these energy-efficient, artificial conditions that are sufficient to support growth. Research needs to be done to determine how to maximize output or yields with fewer photons of light or colors of light. Research is going to focus on economic viability. I expect the pharmaceutical companies will get involved in this research.

“My interests are much more about food and how we create the next generation of profitable growers and higher nutrient crops that are more readily available for consumers. That’s what gets me fired up.”

While matching the genetics to fit the environment is important, Folta said researchers also need to be looking at limiting the environment.

“At the same time that we are looking at the breeding and genetics, we are also looking at how we can deliver shorter pulses of light that still maintain the same output,” he said. “We have cut energy application by 50-80 percent and grown comparable products. The viability of these systems has come from people who have focused on the diminishing return of light efficiency. What they need to work on is the plant efficiency. That is something that is extremely viable.”

Folta said all of the research he has been focused on is with small format, high value crops, including lettuces, sprouts and microgreens.

“Our university does not have the facilities to conduct the necessary experiments,” he said. “But we are partnering with others to do that. We will have good access to larger spaces in the upcoming months. It’s less likely that this type of production would be done with crops that take more space like melons. We are looking at plants where the vegetative portions of the plants are eaten. If you consider a head of lettuce, every photon that is invested results in the plant structure. With a crop like tomatoes, 80-90 percent of the biomass is being thrown away or composted.

Kevin Folta at the University of Florida is interested in how to create the next generation of profitable growers and higher nutrient crops that are more readily available to consumers.

“Growing the plants in shorter production times, shorter supply chains, better postharvest quality because of shorter supply chains, possibly lower costs, a lower carbon footprint and access to local markets, these are the issues I want to address. I see this being done with lettuces, microgreens and herbs such as cilantro and basil. Not so much with corn or melons where a huge amount of energy is invested in a relative small return in terms of calories. These types of crops do better using the sun.”

Folta said 15 years ago people thought the idea of light recipes and changing the spectrum was a crazy and senseless idea.

“Researchers and light manufacturers thought mixtures of red and blue light were all that was needed to grow plants in controlled environments, so there wasn’t any concern about doing anything different,” he said. “Now people understand that green, far red and UV light have important roles and that light quality should change throughout the day. With that in mind, it gives us some flexibility when it comes to changing the production environment, which is a really good thing.”


For more: Kevin Folta, University of Florida, Horticultural Sciences Department, Gainesville, FL 32611;;

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

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Growers, researchers learning how, where and when to use supplemental lighting

Before growers invest in supplemental lighting they need to determine the impact of natural light levels on their crops.

One of the things that University of Florida horticulture professor Celina Gómez tries to reinforce with growers when talking about supplemental lighting is the importance of the daily light integral. Daily light integral is the sum of photosynthetic light (photosynthetically active radiation) received by plants in a day. Gómez did a presentation on “Yield Responses to Supplemental Lighting” at the Northeast Greenhouse Conference in November.

“Solar DLI will determine the light intensities that growers need and for how long they will need to run supplemental lights or even if they need supplemental light,” Gómez said. “Growers should be aware of the DLI whether they are growing greenhouse vegetable or ornamental crops. It is one of the most critical factors.

“Fruiting vegetable crops have a fairly high DLI requirement, usually between 20-25 moles of light per square meter per day (mol·m-2·d-1). For most ornamental crops, the DLI won’t likely be more than 12 moles since growers are not trying to develop fruit.”

Celina Gómez, environmental horticulture professor at University of Florida, said knowing the solar DLI will determine a grower’s need for supplemental lighting.
Photos courtesy of Celina Gómez, Univ. of Fla.

Gómez said growers may find it difficult to determine the optimal DLI for various crops.

“This information isn’t the easiest to find and there can be differences between similar species,” she said. “Finding the optimal DLI can be especially difficult to find for uncommon horticultural crops. During my presentation I had one greenhouse grower ask me about the optimal DLI for potato seed production.”

While knowing a plant’s DLI is important, Gómez said it is just as important for growers to know how much light is being delivered by the sun.

“Knowing what a crop is getting from the sun will determine how much a grower is going to need supplemental light or if he even needs supplemental light,” she said. “A grower may benefit from supplemental light for only a few months or for most of the entire year depending on the crop and its DLI.”

More accurate light measurement

Gómez said one area where growers are making progress is how they are measuring light intensity.

“After so many years of talking about the best way to measure light that is useful to plants, growers are realizing how to more accurately measure light,” she said. “They realize the importance of monitoring the light intensity that their plants receive from sunlight.

“I expect that more growers have invested in quantum sensors to measure light intensity and if they are still using light meters they realize they have to be able to figure out how to convert those readings that makes sense in regards to plant growth. The growers are getting it and making the conversions from footcandles to other metrics like moles.”

Still learning about LEDs

Even though growers better understand the importance of DLI, Gómez said growers can still be overwhelmed by the choice of supplemental lights available, including high pressure sodium (HPS) and light emitting diodes (LEDs).

“Most growers don’t know exactly what specific wavelengths or spectrum or what light recipe are best for their crops,” she said. “In the case of LEDs, most growers are choosing white LEDs or a combination of colors like red and blue. When I started my PhD in 2011, most available LED arrays came in combinations of red and blue. More LED light manufacturers are adding wavelengths to their range, but most commercial LED units come with fixed wavelengths.

“Most growers don’t know which specific wavelengths work best for their crops. They are relying on what they are told by the LED manufacturers. If the growers know what they want to do with a crop, then the university researchers working with the LED manufacturers could be able to advise growers on what LED lights they should be using. It’s also going to be cheaper for the light companies to manufacture fixtures with a standard recipe than to try to come up with a specific recipe for every grower.”

Gómez said LEDs have been more widely adapted by controlled environment agriculture growers operating vertical farms and warehouse facilities.

LEDs have been widely adapted by controlled environment agriculture growers operating vertical farms and warehouse facilities.
Photo courtesy of Farmbox Greens

“While an increasing number of greenhouse growers are interested in LEDs, more of these growers are still using high pressure sodium lamps,” she said. “I generally don’t recommend that greenhouse growers switch from HPS to LEDs just yet. There is more information that needs to be determined for LEDs. HPS is the more established technology and greenhouse growers know what they are getting with these lamps in regards to light intensity, light quality and lifespan. When it comes to greenhouse applications, LEDs can still be considered a high risk technology for growers. Most greenhouse growers are still waiting to make the transition from HPS to LEDs.”

Additional LED research

Gómez said many of the research papers published about LEDs have focused on the effect of light quality or spectrum on several different crops.
“A lot of the plant responses are also affected and dependent on the intensity of light or light quantity– high light vs. low light,” she said. “Under different light intensities plants are going to have different responses. There is also the potential for differences in cultivar responses. Most growers are not going to use a specific red, blue, far-red, white, whatever ratio of light quality for one particular cultivar when they have hundreds of different cultivars in their production facilities.”

Another area Gómez said still has to be determined is the lifetime of the LEDs used in production greenhouses.

“This has to do with the greenhouse production environment where there can be high temperatures, high humidity and chemical application residues,” she said. “The life expectancy of a LED installed in a greenhouse in Alaska is not likely to be the same as the life expectancy in a greenhouse in Indiana due to the different environmental conditions within the greenhouses.”

Another area that Gómez said could use more research is the area of LED interlighting or intracanopy lighting.

“This is something that we were interested in when I was a student at Purdue University,” she said. “This use of LEDs even has potential applications in areas that have high light levels.

“There can be a lot of shading within the plant canopies of high wire crops like tomatoes, cucumbers and peppers, even if the light levels overhead are high. Research still needs to be done with intracanopy lighting and with the light quality of intracanopy lighting. The light quality for this intracanopy lighting may need to be different than the light quality for overhead lighting.”

Gómez said the use of intracanopy lighting could potentially provide light to those leaves that are shaded by the upper canopy or by neighboring plants.

Intracanopy or interlighting LEDs could potentially be used to increase fruit number, fruit size and fruit quality of high wire crops like tomato.

“Those leaves may be receiving low levels of light and not photosynthesizing so they are not contributing to the photosynthetic production of the plant,” she said. “There is the potential of using intracanopy lighting to increase the photosynthetic activity. We don’t know yet if that is true or if that is even going to make a difference in terms of production.

“We don’t know if the plants have already reached their maximum genetic potential. We may find out that there is increased photosynthetic activity with intracanopy lighting. The increase in overall production could include number of fruit and size of fruit. Another benefit is that a specific light wavelength could increase fruit quality. That could potentially be done with intracanopy lighting by placing the fixture close to the fruit clusters. In the case of tomatoes the levels of beneficial compounds like lycopene might be able to be increased.”


For more: Celina Gómez, University of Florida, Department of Environmental Horticulture, Gainesville, FL 32611-0670; (352) 273-4568;;

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

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Online fertilizer training course from University of Florida begins on July 18

University of Florida Nutrient Management Course

University of Florida Nutrient Management CourseThe online course “Nutrient Management (Level 1)/Manejo de Nutrientes (Nivel 1)” offered by University of Florida IFAS Extension (UF) helps growers make better crop management decisions. This course is designed for US and international growers that have practical experience or entry university level, and are in production, technical or sales roles. The course is offered in English and Spanish. Topics covered include common nutrient problems, essential nutrients, fertilizer types and how to interpret a fertilizer label, managing total nutrient level, pH and EC and onsite testing, and growing media.


The course runs for 4 weeks, from July 18 to August 12, 2016. Cost is $US200 per participant, and includes a personalized certificate of completion. Each week there are two streaming video lessons, readings and assignments (about 3-4 hours total commitment per week), which can be accessed at any time of day. Bilingual PhD instructors can be accessed via text chat and discussion features. Click here to register.

Other courses are available on advanced crop nutrition, weeds, diseases, and greenhouse management. For more information, go to, or contact

PDF: Nutrient Management Central


University of Florida

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University of Florida offers online greenhouse training courses

Growers at all levels of experience can benefits from four week courses.

For the second year, the University of Florida Institute of Food and Agricultural Sciences Extension will be offering online training courses in English and Spanish starting on May 30. The courses are to be geared towards helping grower staffs make better crop management decisions.

Each course runs for 4 weeks, costs $200 per participant, and includes a personalized certificate of completion. Each week there are two streaming video lessons, readings and assignments (about 3-4 hours total commitment per week), which can be accessed at any time of day. Bilingual PhD instructors can be accessed via text chat and discussion features. For more information, go to under “training” and “online courses”.

The schedule of online courses planned for 2016 includes:
The first course, Greenhouse 101, is ideal for new employees, or employees with practical experience but lacking in formal horticulture training. Topics covered are plant parts and functions, photosynthesis and growth, greenhouse technology, flowering, compactness and branching, irrigation, nutrition, and plant health.
Nutrient Management 1, Disease Management and Weed Management are courses geared towards grower staff with some experience and training, or at the entry-university level.
Nutrient Management 2 is an advanced course for the experienced, well-trained grower, those at the upper-university level.
University of Florida
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Plant factories continue to evolve

As technology improves, plant factories have the
potential to operate in the U.S. and Canada to produce crops that are difficult
to grow using current conventional methods.

By David Kuack
When you hear the term “plant factory” what picture comes
to mind? University of Florida professor and mechanical engineer John Schueller
said the traditional definition of a plant factory is a place in which there is
no natural light and artificial light is used to produce plants.
“I’m more of a traditionalist in that I feel a plant
factory is a place that has mainly or only artificial lights in order to grow
plants,” Schueller said. “But a greenhouse with multiple levels of plants in
which natural light is the dominant source and is supplemented with artificial
light, I would also consider that to be a plant factory.
“People involved in protected plant agriculture,
including greenhouses and indoor plant factories, are displaying a lot of
creativity. There are a lot of different systems being tried out. It’s
difficult to make a hard and fast definition of a plant factory. A traditional
greenhouse with plants on raised benches or growing on the floor is not usually
recognized as a plant factory.”
Plant factory

Schueller, who spoke at the Plant Factory Conference in
Kyoto, Japan, in Nov. 2014, said the most important automation that occurs in a
plant factory is during the growth stage.

“The application of light and fertilizer is when the main
automation occurs,” he said. “There is automation during planting when a grower
is trying to establish the plants. And there is also automation during

University of Florida mechanical engineer John
said the technology of plant factories
is improving with the main improvement
occurring with LED lighting.

courtesy of John Schueller, Univ. of Fla.

Schueller said during the Plant Factory Conference there
was a lot of discussion about which lights are the best for using in plant
“There are questions that still need to be answered about
what are the best wavelengths and what are the best cycles for different
crops,” he said “Even though there are a considerable number of plant
factories, we still don’t know what the optimal conditions are for growing
plants. There is a lot of variation and experimentation occurring.”
Schueller said automation in the plant factories will
probably occur with the planting practices before it happens with harvesting.
“In Japanese plant factories the finished plants are
brought to the harvesters,” he said. “There is automation to transfer the
plants. People are doing the harvesting of leafy greens, but they are brought
to the workers at an appropriate height and position so that they can be very
efficient and very productive. Obviously, if there are 14 layers of plants
under lights the plants are moved to the harvesters. But there is still some
human involvement in harvesting the plants.”
Schueller said an advantage to a plant factory is the
ability to precisely control the environment. “The technology is improving,” he
said. “The main improvement is with LED lighting. As LEDs become less expensive
and better that will help in the development of plant factories. Also, less
expensive sensors for measuring nutrient solutions are becoming available. As
growers gain more experience with this technology they get better at
controlling the production environment.”
Plant factory

Schueller said economics play a big role in what will be
feasible in how these factories operate.

“The Japanese market for fresh fruits and vegetables is
much different than in the U.S. and Canada,” he said. “In the U.S. and Canada,
vegetables are cheaper. The market will not bear some of the costs that will be
accepted in Japan. In Japan consumers are willing to pay $40 for a watermelon.
“From an agricultural economic standpoint, it seems to me
the big advantage of a plant factory is that a grower can control the
production situation very well. The disadvantages are the energy costs for
running the artificial lights and the capital equipment costs. The best
opportunity is to produce a product that has certain characteristics, that has
no pesticides applied, that has no bacterial contamination, so that a grower
can demand a premium price for it.”

Schueller said one area of plant factory production
that shows great potential
is being able to develop
techniques that allow high end vegetables to have
nutritional characteristics that can be easily manipulated.

Schueller said one area of plant factory production that
shows great potential is being able to develop techniques that allow high end
vegetables to have nutritional characteristics that can be easily manipulated
more so than in other production environments.
“One of the Japanese plant factories that was built by
Fujitsu is growing lettuce which has a low potassium content,”
he said. “This lettuce is being produced for kidney dialysis patients and
people with chronic kidney disease. This type of crop has a lot of potential
for U.S. and Canadian markets. Developing vegetables that have nutritional
characteristics so that the markets will be able to tolerate higher production
costs that are associated with plant factories.”
Schueller said the plant factories in Japan can produce
leafy green vegetables in about 15 days.
“The production cycle needs to be as short as possible,”
he said. “If a plant factory is controlled properly and maintains sanitary
conditions, it is possible to produce leafy green vegetables with specific
nutrient characteristics without pesticides. For those types of crops a grower
can demand a premium price to pay for the equipment and energy to produce
Fast, precise

Schueller said the plant factories in Asia are producing
primarily leafy green vegetables.

“I expect these crops would have the greatest potential
in the U.S. as well,” he said. “As more consumers move away from iceberg
lettuce and romaine lettuce, they tend to look for other types of lettuce and
leafy greens and microgreens. There might be real potential with these crops
because they can usually be turned much more quickly.”

has over 200 plant factories. One of the reasons that
the country has experienced
a proliferation of these facilities
 is food security. Sixty percent of the country’s
food is imported.

Schueller said some of the issues pushing plant factories
in Asia are related to domestic food production and land availability.
“Japan imports almost 60 percent of its food,” he said.
“For the Japanese it’s an issue of food security. Singapore has increased its
vegetable consumption from 7 percent to 8 percent. In Singapore there is a
limited amount of land. They are looking for ways to maximize food production
and plant factories offer them a solution. With plant factories that have
vertical farming they can push the production to maximize the space. In the
U.S. that isn’t a big concern. The plant factories in the U.S. that will be
successful are the ones that grow products that are difficult to produce using
conventional methods.”

For more: John
Schueller, University of Florida, Departments of Mechanical and Aerospace and Agricultural
and Biological Engineering; (352) 392-0822;

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

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Organic fertilizers provide option to grow more sustainably

Organic fertilizers offer growers another tool for
producing their crops with more sustainable inputs.

By David Kuack
Growers of both food and ornamental crops are facing
increased scrutiny regarding their production practices from the pesticides
they apply to the amount of water and energy they use. In October, Whole Foods
Market launched its Responsibly Grown
program. The company
said the purpose of this new rating system is to assess production practices
that impact human health and the environment. The system labels fresh fruits,
vegetables and flowers as “good,” “better” or “best.” The program also prohibits
the use of some of the hazardous neurotoxins still permitted in agriculture.
If growers implement more sustainable practices to
produce their crops, are consumers willing to pay more for them? A recent University of Florida study
focused on consumers’ willingness to spend more on ornamental plants based on
plant attributes related to sustainable production methods, container types and
origin of production. Consumers were willing to pay up to 16 cents more for
plants grown using energy-saving and sustainable production methods, plants
grown in non-conventional containers and plants grown locally.
Organic fertilizers
show potential

Claudio Pasian, horticulture associate professor at Ohio
State University in Columbus, said an increasing amount of pressure is being
put on growers related to the environment by both retailers and consumers.

“Growers may be forced by their clients to produce more
sustainable products, including more organic products,” Pasian said. “Here in
Ohio, like in other parts of the country, there are concerns with fertilizers
running off into waterways and leaching into ground water. In the future
“fertilizer” may become a taboo word for some people. For some people, perception is
reality. Using an organic fertilizer may help growers achieve a more
sustainable image with retailers and consumers.”

Based on research Pasian has conducted on ornamentals
plants and herbs, he said organic fertilizers look like a promising alternative
to traditional water soluble fertilizers. Like any new product or technology,
he said there are differences between traditional water soluble fertilizers and
organic fertilizers and growers will have to learn how to use them.
Pasian began his research on organic fertilizers as a
result of a substrate manufacturer seeking to conduct trials incorporating
organic fertilizer into some of its consumer growing mixes.
“The company wanted me to run some experiments with a
number of fertilizers,” he said. “There were no liquid organic fertilizers
tested because the purpose of the study was to incorporate the fertilizers into
growing mixes. All of the organic fertilizers tested were in a solid form,
either a powder or small granules. Most of the organic fertilizers were
animal-based. The control plants were treated with a 20-10-20 water soluble
fertilizer at 100 parts per million nitrogen.”
Pasian said two of three annuals (seed geranium, pansy
and petunia) grown with the organic fertilizers did very well. Although the
organically fertilized plants were smaller in size, he said they were
commercially salable.
Petunias grown with Miracle Gro Organic Choice All Purpose 7-1-2
at a rate of 5.9 grams per pot (left), Sustane 8-4-4 at a rate of 5.1 grams
per pot (center) and Osmocote 15-9-12 at a rate of 2.7 grams per
pot (right). Top = side view; Bottom = top view.
Photos courtesy of Claudio Pasian, Ohio State University

Pasian found the only plants that occasionally did not do
well with organic fertilizers were pansies. He has not conducted any further experiments
to determine why there were issues with pansies grown with organic fertilizers.

“I’m not sure why the pansies did not do as well as the
other species,” he said. “There were some phytotoxicity issues. The quality of
the plants was not as good and there was high rate of mortality.”
fertilizer trials

After the initial trials with organic fertilizers showed
positive results, Pasian expanded his research with additional ornamental
plants. He compared incorporating Scotts Miracle Gro Organic Choice and Sustane
organic fertilizers to a controlled-release and water-soluble fertilizers. All
of the plants in the study were grown in 4½-inch pots containing Fafard 3B
bark-based growing mix without a fertilizer charge.

“I grew six annual bedding plant species (angelonia, seed
geranium, hypoestes, impatiens, pansy and petunia) with the different
fertilizers,” he said. “The plant growth for plants fertilized with the
controlled-release fertilizer and water soluble fertilizer were very similar.
In most cases the water-soluble fertilized plants were the largest, followed by
the controlled-release fertilizer and then the organically fertilized plants.
Seed geraniums grown with Peters 20-10-20 water soluble fertilizer
at a rate of 100 ppm nitrogen applied with irrigation as needed (left)
or with a single application of Sustane 8-4-4 at a rate of 2.6 grams
per 4.5-inch container (right).

“The plants grown with the organic fertilizers were
slightly smaller. But overall the organically fertilized plants did well. In
some cases, the plants being smaller could be a positive effect because that
means growers may not have to apply growth regulators.”

Trialing herbs and

Pasian has received a grant from the Horticultural
Research Institute to expand his organic fertilizer study to include herbs and
perennials. He worked with a local grower on the plant selection and chose
three herbs (basil, parsley and thyme) and three perennials (Nepeta cataria, rudbeckia and salvia). Like
the annuals study, the herbs and perennials were grown in 4½-inch pots
containing Fafard 3B bark-based growing mix without a fertilizer charge.

“In the case of basil, the initial application of organic
fertilizer was enough to finish the crop,” Pasian said. “One single application
incorporated into the growing mix before planting the plugs would be sufficient
for the production cycle. For thyme it would be very close to finish with one
application, almost the same as basil.”
Pasian is planning to repeat the trials with parsley
because he encountered some issues with heat stress and disease problems.
“During the parsley trial even the control plants had
problems,” he said. “The plants were grown during the summer so the warm
temperatures in the greenhouse may have contributed to the problems. I expect
when the parsley study is repeated during the winter and the temperatures have
cooled down the results will be different.”
Basil plants grown with Peters 20-10-20 water soluble fertilizer at
a rate of 100 ppm nitrogen applied with irrigation as needed (left)
and three rates of Miracle Gro Organic Choice (from left to right):
5.9, 4.5, or 3 grams per 4.5-inch container.

Pasian said since many perennials are long-term crops,
they will need additional applications of organic fertilizers.

“In the perennial trials, the first flush of growth with
the organic fertilizers was good,” he said. “But then the fertilizers ran out.
Applying a powder or a small granular organic fertilizer to each pot is not
realistic for growers. These organic fertilizers can be incorporated into the
growing mix prior to planting. Once these fertilizers are used by the plants, which
takes about five to six weeks, a grower can start applying a liquid organic
fertilizer. This could be a fish emulsion or similar type fertilizer.
“One single organic fertilizer application incorporated
into the growing mix is not enough. Additional fertilizer will need to be
applied probably more than once. The plants grew decently with one application,
but if larger plants are the goal then more fertilizer is going to be needed.”
Nepeta cataria
(catnip) grew very fast initially and was the first perennial to show
deficiency symptoms. Pasian said nepeta would require additional fertilizer
applications sooner.
Rudbeckia took much longer to show any deficiencies.
Pasian said since rudbeckia is a very slow crop with a longer production time,
it will need supplemental fertilizer applications.
“Organically fertilized rudbeckia produced a first flush
of growth that was as good as plants fed with water soluble and controlled-release
fertilizers,” he said. “But as time went on during production, the organically fertilized
plants needed another shot of fertilizer.
“I consider salvia to be an intermediate crop between
catnip and rudbeckia. I expect that salvia will require additional fertilizer
Pasian will continue the trial with the same herbs and
perennials this winter and coming spring. The plants will be grown in 1-gallon
containers to match commercial production practices.
“This research is not being conducted with the goal of
changing how fertilization is done by most growers,” Pasian said. “Water soluble
fertilizers are excellent products that growers use successfully. This research
will provide growers with information on how to produce a crop that has been
fertilized in a more sustainable way to satisfy a small percent of their clients.
“Marketing is going to be the issue for growers. If they
grow plants with both organic and water soluble fertilizers, those grown with
the organic fertilizer are going to have to be marketed differently so the
consumers know the difference and can make their choice about which plants to

For more:
Claudio Pasian, Ohio State University, Department of Horticulture and Crop
Science, (614) 292-9941;

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

Visit our corporate website at

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Using LEDs to manipulate plant growth, characteristics

With the ability to deliver specific light wavelengths
with LED lights, growers, retailers and consumers could eventually manipulate
the scent, color, flavor, postharvest life and other characteristics of
ornamental and edible crops.

By David Kuack

Both ornamental and edible plant growers are using
supplemental lighting. Some use light to control photoperiod. Others use
supplemental light to hasten plant development by increasing the rate of

What if you could use light to increase the flavor,
aroma, color intensity, insect and disease resistance and postharvest life of
edible crops? What if you could use light to increase the fragrance, color
intensity, insect and disease resistance, flower timing and postharvest life of
ornamental flowering plants? Sound like science fiction? Read on.

Talking to plants

Kevin Folta, interim chair and associate professor of the
Horticultural Sciences Department at the University of Florida, said the
fundamental idea of using light to manipulate plants is an old one.

“We’ve known for a long time that light can affect
photosynthesis, but we are now starting to understand how light can regulate specific
plant responses,” Folta said. “It’s no big surprise that light could manipulate
something like flavors or any other aspect of plant metabolism.”

Working with other scientists at the university’s
Institute for Plant Innovation, Folta said
initial research indicates red, far red and blue light are the three major
wavelengths that affect volatile accumulation in plants. The researchers have
studied the impact of light wavelengths on strawberries, blueberries, tomatoes
and petunias.

“Volatiles are the chemicals that contribute to the aroma
and flavor that are released,” Folta said. “Volatiles are the chemicals that
are emitted that allow you to smell and taste a piece of fruit. These are the
compounds that are really important in providing flavor to fruit and

University of Florida associate professor Kevin Folta and other
scientists at the university’s Institute for Plant Innovation are
studying the impact specific light wavelengths can have on
plant characteristics.
Photo by Tyler Jones, UF/IFAS Photography  

 Folta said similar changes could be made to flowering
plants by manipulating the light wavelengths that the plants are exposed to.

“For ornamentals we could affect aromas, colors and
flower timing by changing the light environment—the specific wavelengths,” he
said. “It would be possible to synchronize an entire greenhouse of plants to
flower at the same time just by flipping a switch. By understanding the light
spectrum and how a plant sees it, it could allow us to manipulate how a plant

“It’s almost like we can talk to the plants. It’s a
language that is essentially a vocabulary of light wavelengths and that we can
use to influence how a plant grows.”

Focused on LEDs

Folta said all of the research being done involves the
use of LED lights.

“LEDs allow us to deliver very precise amounts of
specific wavelengths,” he said. “LEDs allow us to mix the light conditions
precisely. We can pick and choose the light we want to use.”

Folta said one of the ways different light wavelengths
could be used is to customize what the final fruit, vegetable or flower would
look, taste and smell like.

“For example, maybe we could put the plants under blue
light for a few days and then switch to far red and then red. We know that such
sequential treatments allow us to bump up the pigments, then the nutrients and
then the flavors,” he said. “This treatment could change the way we grow, ship
and sell crops, as well as how consumers store them at home.

“All plant traits are a combination of genetics and the
environment. The genetics are already in place to make a quality fruit,
vegetable or flower, so the LEDs allow us to manipulate what’s already there.
We can tweak the environment with the LEDs to alter plant characteristics.
Maybe an LED light would be placed in a box of roses. When a consumer opens the
box there would be this incredible aroma released.”

Folta said the research has tremendous potential for both
edible and ornamental crops.

“This research would probably have happened a longtime
ago, but LED lights were prohibitively expensive,” he said. “Now that the cost
of LEDs and narrow band width lighting is becoming more affordable, we realistically
see LED arrays being used in greenhouses to manipulate the way plants grow.”

Endless potential

Although the initial research has focused on changing the
taste of fruit and vegetables, Folta said the use of light could easily be
expanded to manipulate other plant characteristics.

Kevin Folta said growers may eventually be able to synchronize
an entire greenhouse of plants to flower at the same time just
by flipping a switch for LED lights.
Photo by Tyler Jones, UF/IFAS Photography

“There is an increasing body of research literature that
indicates some of the compounds emitted by plants and their fruit deter insects
or deter fungal growth,” he said. “It may be possible that we could affect
insect and disease resistance. For example, by using LED lights we could change
the metabolic profile of the plant so that poinsettias would be more resistant
to whitefly. This might be done by stopping production of plant compounds that
attract whiteflies, or producing compounds that scare them away or even better
than that may attract a predator of the whitefly.

“What we are doing is manipulating the plant metabolism
or changing it in ways that we don’t necessarily understand 100 percent yet,
but we know we can do it.”

An example of one of the results of the research he
doesn’t completely understand has occurred with strawberry plants.

“In the lab we have exposed strawberry plants to LED
lights and they don’t get spider mites,” he said. “We don’t know if there is
something that the LEDs are doing to change the development of the spider mite.
Or the light maybe doing something to the plant that causes it to produce a
chemical the spider mites don’t like so they choose to go to a different plant.
This is something that we still need to test.”

Folta said most of the previous research that involved
the same type of plant process manipulation involved inserting a gene, spraying
a chemical or other types of treatments that were labor intensive and required
other inputs.

“Now we are looking at basically flipping a switch to
turn on a low energy device,” he said. “Adding value at a low cost would be a
great thing for the horticulture industry.”

For more: Kevin
Folta, University of Florida, Horticultural Sciences Department, (352) 273-4812

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

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