OHCEAC Conference Recap: Transplant Production for Low- and High-Tech Farms
August 26, 2025 
This year's OHCEAC Conference took place at OSU's Controlled Environment Agriculture Research Complex (CEARC) in Columbus, Ohio.
On July 16, The Ohio State University’s Ohio Controlled Environment Agriculture Center (OHCEAC) hosted its fourth annual conference in partnership with the CEA Coalition at North Carolina State University (NC State) in Columbus, Ohio. The topic for 2025 was “Advancement of High-Quality Transplant Production Technologies Under Controlled Environments,” and the sessions covered transplant production in CEA, floriculture, and forestry.
Two presentations were especially relevant to CEA growers:
- “Production and Use of High-Quality Vegetable Seedlings and Grafting for High Tunnels and Open Fields,” by Matt Kleinhenz, Ph.D., professor of horticulture at OSU.
- “Optimized High-Tech CEA Propagation Strategies for Affordable, High-Quality Young Plants,” by Ricardo Hernandez, Ph.D., head of the CEA Coalition.
Here’s an overview of each presentation and the key takeaways for high- and low-tech operations.
Producing Seedlings for High Tunnels and Open Fields
Dr. Kleinhenz began the session by defining “seedling” (part of a plant that detaches to produce new life) and the traits that distinguish high-quality seedlings from low-quality ones. The best-quality seedlings share these traits:
- Disease-free
- Insect-free
- Lack of abiotic stress
- Ideal root-shoot ratio
- Sturdiness
- Uniformity.
In cultivating seedlings, he said, growers face several challenges. For starters, outdoor growers can’t control the levels of time, sun, water, and nutrients their plants receive every season—and anything that interferes with these resources affects seedling quality. In most cases, growers struggle to achieve plant uniformity in seedling transplants due to soil health and planting depth. Growers also encounter sustainability challenges, as the current status quo of seeding production entails starting seeds in plastic trays before planting them in a high tunnel, greenhouse, or vertical farm.
Dr. Kleinhenz presented three potential solutions for problems surrounding vigor and sustainability in vegetable seedling production:
- Seed-to-plant calculator: Dr. Kleinhenz and his team developed a calculator for growers to estimate seedling vigor. This tool helps growers determine the right time to plant their seedlings so they’re ready to be transplanted at the same time.
- Carpet media: Dr. Kleinhenz and one of his graduate students worked with Great Lakes Natural Fibers to grow a “carpet” of leafy vegetable crops using natural fibers. They planted seedlings in wool fabric and installed it in a high tunnel. By the end of the study, they found that growers can grow more high-density crops in wool than individual plastic containers–using carpet media also improves sustainability significantly.
- Blocking media: Growers compress soil into “blocks” and plant seedlings inside of each one. Then, they plant the block directly into the ground–this mimics typical seedling containers, but without using plastic trays.
With these approaches, according to Dr. Kleinhenz, outdoor growers will have a much easier time producing the right amount of quality plants when their farm needs them (or other farms need them)—and do so sustainably.
High-Tech Propagation Strategies for Seedling Production
Before launching into his presentation, which covered both lighting and CO2 enrichment in various crops, Dr. Hernandez emphasized how high-tech growers have an advantage when it comes to seedling production. Unlike high tunnel users, indoor farmers have complete control over their growing conditions and can rely on sensors and lighting to create their desired environment. Here are the main considerations he took into account in his research:
- Optimization: Which light spectrum is best suited for the propagation of seedlings in greenhouses and vertical farms.
- High-tech strategies: How pulling different environmental levers (sensors, lighting, etc.) can help grow healthy seedlings.
- Maintaining high-quality young plants with healthy biomass and morphology via the right lighting.
- Increasing production affordability by optimizing the lighting and CO2 levels.
Dr. Hernandez has focused heavily on manipulating the light spectrum to create ideal growing conditions in vertical farms and high-tech greenhouses. “We looked at LED lights with different spectra, mainly blue, red, and white, to see which would produce a high-quality plant,” he explained.
In greenhouses where supplemental lighting is used, he found that light intensity was the most critical parameter. In systems that use sole-source lighting, he found that certain spectra offer competitive advantages for specific plant species. For fully indoor operations that grow multiple types of plants, he found that broad-spectrum white light offered the highest amount of flexibility.
In addition to his research with lighting, Dr. Hernandez explored CO2 enrichment with various CEA crops (tomatoes, watermelon, cucumbers, and strawberries) to see how different concentrations of CO2 affected his research considerations listed above.
In indoor environments, Dr. Hernandez said the highest amount of CO2 that growers should use is between 600-700 parts per million. But in young plants and seedlings the CO2 cap is higher—in this study, he reached 1600 parts per million. After testing enhanced levels of CO2, Dr. Hernandez discovered that higher CO2 levels for seedlings improved plant biomass and cost less than maintaining ambient CO2.
By the end of his study, Dr. Hernandez found that CO2 enrichment, though crop-specific, is affordable in indoor propagation systems–in comparison, light intensity increases come with a significant deployment cost. He concluded that co-optimizing both light intensity and CO2 enrichment provides growers with the most benefits.
For more information about this year’s OHCEAC Conference and the featured speakers, go here: https://ohceac.osu.edu/ohceac_annual_conference.