When it comes to greenhouse efficiency and energy savings, what readily comes to mind is the type of fuel source or heating system that is in place, or perhaps the greenhouse covering. Lost in the shuffle of flats, trays and pots is the very surface these items occupy.
Getting it right
The right bench system can save money and improve efficiency. Just ask Steve Castorani, president and CEO of North Creek Nurseries, in Landenberg, Pa.
North Creek is a well-known greenhouse operation that grows plugs — mostly native perennials, ferns and grasses. The company was founded 29 years ago with a few greenhouses and has turned into a formidable supplier of starter material to perennial plant growers along the East Coast, the Midwest and Canada.
In 2013, Castorani decided it was time for an expansion and upgrade to the operation. During the construction phase, Castorani and General Manager Tim McGinty mulled over what they were going to have installed for flooring and benches.
They decided on concrete flooring with in-floor heating, fueled by natural gas with an oil-fired hot water boiler. For a bench system they went with “Grow-n-Go Racks,” manufactured by Agrinomix, after hearing about them at Cultivate'17 and seeing them in use at Timbuk Farms in Granville, Ohio.
Pouring concrete into the greenhouses and purchasing new bench systems was not cheap. However, Castorani and McGinty were able to justify the expense by strategically configuring the greenhouses to provide heat to the plants on the racks in the most efficient way.
“The concrete floor gives us a thermal mass, so it is much more energy efficient,” Castorani says. To ensure heat goes directly where it is needed — to the root zone of the plant — they had the floor and sides well-insulated. Keeping the heat from escaping the houses is a curtain suspended over the grow benches, just below the gutters.
As Castorani explains it, the Grow-n-Go Racks transportation and growing system is a series of trays the size of a pallet. Each tray has legs that are about 8 inches high, allowing air movement and drainage underneath for the plants on the benches. The trays are constructed of galvanized expanded metal. Each tray holds 10 flats, which theoretically can be lifted by two able-bodied workers. However, North Creek’s perennial trays are a little heavier than annual trays other growers are moving around in a greenhouse.
“We figured everyone is going to go out with back injuries,” Castorani says. “So, we purchased a forklift,” which he said required a minor learning curve to maneuver it around the houses and shuffling trays, but it is working out just fine now. When it’s time to move the trays out of the bay, it’s pretty easy.
“We’re able to move 10 flats at a time,” McGinty says. “One person and a forklift sets them down and picks them up; basically, when we’re moving product we’ve eliminated three people.”
McGinty is happy with the new bench system and wonders why nobody thought of the idea sooner.
“They cost $2.68 a square foot,” McGinty says. “You can’t touch a bench for that — you get a bench and a transportation system.” As for energy savings, Castorani says a recent energy audit revealed that the new greenhouse configuration is 78 percent more efficient than the old 30-foot ground-to-ground houses they used prior to the upgrade.
Lightweight benches and tables
For growers who have already invested in grow tables, whether they be wood or metal, there is a lightweight option to consider for both tables and bench systems. Agri of Virginia Inc. manufacturers two lightweight benchtops measuring 18 by 36 inches and 2 by 4 feet, respectively. They sell the bench tops and other growing systems to greenhouse growers, as well as institutions, including schools, correctional facilities and rehabilitation centers.
General Manager Jim Showalter pointed out several advantages of these bench tops, including the fact that they are lightweight, easy to clean, and you don’t have the potential for injury from metal sticking up or shards of steel getting lodged underneath your fingernails.
“You have a safety factor, especially in an institutional setting,” Showalter says. “Because we don’t have wires sticking out that people can snag their hands on — it’s especially important in a school setting.”
These UV-protected plastic bench tops are a hit with workers due to the way trays slide effortlessly along the surface. This saves workers from having to pick each tray up individually and move it.
“We’ve had people who put the plastic bench tops in only one of their structures and they call back and say, ‘Jim, everybody is fighting because they want to work in that building.’”
Plastic table tops are potentially more sanitary than wood table tops. “Cleanliness and hygiene is a huge advantage of plastic because things you don’t want in a greenhouse, such as algae, mold and fungus, don’t tend to grow on an inorganic product like polypropylene,” Showalter says.
The company also manufactures fiberglass tables, which have some of the advantages of the bench tops in terms of sanitation and being lightweight. Showalter admits that these tables are pricey and may not be affordable for growers with several acres of greenhouses. Still, they are an option for growers looking to upgrade to state-of-the-art greenhouse equipment.
“A complete bench with fiberglass frame is going to be costly but it is the best value,” Showalter says. “It’s coming on,” he says of the increasing popularity of the poly-plastic bench systems.
“Some still want to keep the wire they have,” he continues. “I would say the folks who are more progressive and open to improvement and to better ideas and so forth will definitely look at the plastic.”
Other bench options
Wood benches: Treated wood with nontoxic chemicals is a fairly cost-effective option for growers. However, being porous, wood can cause bacteria, fungi and mold to accumulate, according to Showalter. Wood benches are also heavy and more labor-intensive when it comes time to turn them over and clean them or to move them around.
Expanded metal benches: These are durable but then will rust and corrode over time and are known for having sharp edges that can cause minor cuts and clothes to rip, becoming a potential source of liability for owners, Showalter says.
Rolling benches: Rolling benches were considered a major innovation for greenhouse growers several years ago. They allow growers to utilize aisle space in a greenhouse that would otherwise be wasted, so they are still a good option.