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Greenhouse Management: Why did you decide to pursue horticulture as a career path?
Amanda Hershberger: Life is not a straight line, so I had graduated from high school and spent a year off saving money for college so I could pay for it. Then I had gone to a community college and then transferred my credits to go into horticulture. But how I got interested in horticulture was kind of an accident. I grew up in an apartment, so we didn’t have many plants around. I had gotten a job before going to community college as an administrative assistant at a person’s house. And he had all these dead and dying plants all around the house. I said, ‘I can’t just answer calls all day,’ so I went around and started watering plants and they started to come back to life. I loved it and I decided that’s what I was going to do. My initial intention was to work in a zoo, but then I learned that people developed the plants that go into landscapes at places like the zoo and that just seemed like something I would like to do. There’s a real art to it. I get to make a positive impact on the industry and work with plants all day.
GM: What is a work day like for a plant breeder?
AH: It really depends on the day. I work with disease resistance and one of the plants I work with are vinca. My goal is to spend as much time with the plants as possible. But half of it is administrative work on the computer, so you try to get good at that so you can spend more time with the plants. Like, what I’m going to do today is make a transplant list, finalizing disease results and determining what could be used for crossing for potential commercial product. Or [on another day] it could be making sure seed harvest happens on time. Or I could be talking to our production facility, making sure that all the requests I have asked for are going through. I’m fortunate that I’m given a lot of freedom as long as I’m following through on what the company is asking.
GM: What are some things you didn’t expect to encounter in this career, but you’ve since come to love?
AH: I don’t think anyone anticipates how much you need to work with others to make things happen, especially when you’re working with high-volume products. You’ve got an entire team of people you’re working with and without them, you will not see success. You have to be proactive and responsive. One [other] thing that I didn’t expect that I really, really love is working with our production facility. We have a number of them, and the one I specifically work with is in Guatemala and they are amazing people. We run a number of breeding and production projects there, so they’ve been hugely instrumental in getting our products released. Most specific to me is the Cora XDR, which is the new series I had started working on in 2012. I talk to them every two to three weeks and visit them two to three times a year. I love all of it.
Have you had the efficiency of your heating system checked recently? In doing energy audits, I have seen efficiencies on old furnaces and boilers that were less than 70%. The fuel savings with a new unit having 90% or higher efficiency can have a short payback and also reduce typical maintenance problems that keep you up on cold nights. Most manufacturers now include condensing heaters and boilers in their product lines.
How is this high efficiency achieved as compared to conventional units that typically operate at 80 to 85%? When fuel oil, propane and natural gas are burned, steam is one of the byproducts. Burning 1 gallon of fuel oil will produce about 0.98 gallons of water, 1 gallon of propane about 0.82 gallons and 1 ccf of natural gas about 1.16 gallons. In a non-condensing boiler or furnace, this water vapor, which has a temperature of 400 to 500°F, along with the other byproducts, normally goes up the stack and is exhausted into the atmosphere. The high temperature is needed to avoid excessive flue condensation or damage to the boiler from the acidic condensate.
A condensing boiler incorporates an extra heat exchanger in the flue gas exhaust system so that the water vapor condenses back to a liquid. This process captures up to 8000 Btu of heat per gallon of condensate, which is as much as 13% of the original fuel energy. The condensate heats the incoming air (if an air to air heat exchanger is used) or pre-heats the water (if an air to water heat exchanger is used). After the heat is removed, the low-temperature condensate water can be drained through a corrosion resistant pipe (usually PVC), eliminating the need for a chimney.
Condensing boilers have to have low return water from the radiators to work best. With water at 130°F, 15% of the water vapor will condense, whereas at 60°F, over 90% of the water vapor will condense. A root zone system with return water at 80 to 90°F is a good example of where it will work well.
The efficiency is also affected by the humidity of the air. Under the right operating conditions, condensing boilers can achieve an efficiency of 95% or more.
Most heating units with condensing capability have modulating burners that are capable of multiple firing rates. By using embedded control, the firing rate is matched to the heat load needed to give best performance. This means that at high firing rates, the efficiency may decrease but never be less than a conventional boiler.
Today's boilers are much smaller than the old standard units as they have much less water in the jacket. They are self-contained so that much of the wiring and plumbing is done before you receive it. This reduces installation time considerably.
Avoid too large a boiler
Oversizing a boiler can reduce efficiency as the object is to have it run continuously. This is done by adjusting the firing rate — low fire when minimum heat is needed and high fire for the coldest weather. Cycling decreases efficiency from start-up and shut-down operation and increases wear on the boiler. To get the greatest benefit from a condensing unit, it is better to size the boiler for an average winter temperature, not the normal coldest temperature frequently used by engineers. The more continuous operation will keep up with the heat needs better than a unit that cycles.
For condensing hot air unit heaters that only have one firing rate, staging multiple heaters to operate at different temperatures can provide a more uniform greenhouse temperature and save fuel. HAF air circulation can be used to keep a uniform temperature in the greenhouse.
Provide adequate radiation
Typical non-condensing boiler systems are usually designed for 180°F water temperature with fin radiation having an output of about 600 Btu/linear foot.
With condensing systems, additional radiation is needed to provide the needed heat. PEX tubing in the floor, low output fin under the benches or overhead or root zone heat on the benches is commonly used to get the required heat. Installing a condensing boiler with your present radiation system will probably not provide the savings you expect.
Although condensing boilers and heaters are more expensive than conventional units, the greater efficiency can offset the additional cost. USDA Natural Resource and Conservation Service funding may also provide an incentive to make the change.
John is an agricultural engineer, an emeritus extension professor at the University of Connecticut and a regular contributor to Greenhouse Management. He is an author, consultant and certified technical service provider doing greenhouse energy audits for USDA grant programs in New England. email@example.com
As you look around your facility trying to figure out where you are going to get more space for next year’s spring crops, look beyond the walls — or glazing material. While greenhouses offer the most controllable (and protected) climates, they are also expensive spaces to build and operate. For shoulder-season production, look for different spaces to grow your crops.
Retractable-roof greenhouses offer opportunities to take advantage of both a controlled and outdoor environment. When outdoor conditions are agreeable with crop requirements, growing plants under outdoor conditions can result in improved plant quality and lower operating costs. However, for those shoulder seasons where weather is neither consistently poor nor great, retractable-roof greenhouses are an excellent choice.
Retractable-roof greenhouses can provide all the benefits of an outdoor environment — air movement, bright light, etc. — which results in toned growth and high-quality finished plants. However, retractable roofs also mitigate the risks associated with outdoor production by excluding unwanted precipitation, so you can control the substrate moisture and fertility. Additionally, unit heaters installed in retractable-roof greenhouses can keep temperatures in ranges from keeping warm to actively growing. An efficient heating method for retractable-roof greenhouses is to use root-zone heating or plants grown on the ground.
High tunnels or hoop houses, for the purpose of this article, are single-wall film-plastic-covered structures, usually with roll-up or -down sidewalls. These have been increasing in popularity for extending the season for field-grown fruits and vegetables, as well as cut flower production. However, they also are useful for finishing seasonal crops.
Recent research shows high-quality annual bedding plants can be grown in high tunnels. Like with a retractable-roof structure, you can get the benefits of an outdoor-grown crop along with some protection.
Even though you have a protective structure, you’ll still need to watch for temperatures in high tunnels. There are several approaches to this. First, watch your planting date. While plants in a high tunnel can experience very warm days when outdoor temperatures are cold, plants can cool down to the ambient outdoor temperature (or lower!) during the night due to radiant heat loss. Make sure early plantings focus on more cold-tolerant crops.
High tunnels are not for every crop — finishing cold-tolerant petunias (Petunia × hybrida) can be great, while cold-sensitive angelonia (Angelonia angustifolia) are less amenable to this strategy. Additionally, those approaches used to protect plants from frost outdoors, such as pulling spun-fabric netting over crops, can be used in high tunnels on cold nights.
Finishing flowering crops outside is not unusual. In fact, it can be quite common in several locations where the climate is favorable to outdoor production. But even in less-than-ideal climates, there are opportunities to use outdoor space to finish your crops. Maybe you have some room on your fall mum finishing pads that could be used for some of your production? You’ll need to look at the outdoor temperatures and the species you are growing to determine when you can move production outdoors. While it likely will not be used for your earliest crops, outdoor space becomes more useful with each successive turn, as outdoor temperatures improve.
For crops grown outdoors, you will need to think about fertilization in addition to temperatures. Unprotected crops outdoors can leach nutrients when rain falls. As a result, using controlled-release fertilizers (CRFs) can help in providing some nutrition after precipitation, when fertigating may be undesirable. However, for early-season spring crops and late-season fall crops, when outdoor temperatures are cooler, CRF release will have slower nutrient release due to the cooler temperatures.
While retractable-roof greenhouses, high tunnels and outdoors are less-predictable and controllable than greenhouses, they provide opportunities to produce high quality plants while reducing costs. Careful crop selection, planning and scheduling, and a watchful eye can enable growers to take advantage of these affordable production spaces.
Christopher is an assistant professor of horticulture in the Department of Horticulture at Iowa State University. firstname.lastname@example.org
Pam Oldfield ended up in horticulture simply by being in the right place at the right time.
She happened to live across the street from a greenhouse that specialized in interior foliage. One day, about 40 years ago, a man from the greenhouse walked over looking for extra help. Oldfield, who was 18 at the time, agreed to lend a hand and as soon as she walked into the greenhouse, she immediately felt at home.
“We all get into this business because we love what we do and we stay in it because of that,” says Oldfield, an avid home gardener. “I’m blessed because it’s a good fit.”
Oldfield spent 10 years working at an interiorscape company in San Antonio, where she helped with plant installations. Later, she began to learn about the growing side of the business while working at a small operation in Alabama.
When she joined Oelschig Nursery in 1998, Oldfield continued to advance her career as she learned from third-generation business patriarch George Oelschig and head grower, Kenneth Cottros — who worked at the nursery over 50 years before retiring.
“They helped me learn the ropes as I worked my way up,” Oldfield says. Now, as Oelschig’s head grower and production manager, Oldfield wants to give other young, aspiring growers the same opportunities to learn on the job as she passes down her knowledge to the next generation.
Passing along knowledge
As head grower, Oldfield oversees nine growers at Oelschig Nursery, a wholesale greenhouse in Savannah, Georgia, that grows annuals and perennials, along with some seasonal crops and tropical plants. Most of her team is fairly new to growing — like she was when she joined the company — so she considers them apprentices.
In fact, she’s even training her future replacement: head grower-in-training Eric Thrower — the grandson of Kenneth Cottros, who trained Oldfield as his replacement several decades ago. Oldfield meets with Thrower every morning to discuss the day’s priorities and then they scout the greenhouses together to identify any issues that need attention. The nursery spans 15 acres total, with about 7 acres under production — approximately 3 of which are covered.
“We walk the crops all day long, looking and talking about what needs what,” Oldfield says. “Communication is key because the details are critical when you’re dealing with crops and making sure they’re progressing on schedule.”
In turn, Thrower is responsible for training and overseeing the other growers. The entire team meets weekly to review “why we’re doing what we’re doing and how we’re doing it,” says Oldfield, who also manages 15 employees on the production side. “I love to be able to pass it on and help someone else learn like I did.”
Oldfield says it’s easier for young growers to learn the trade today than it was 40 years ago.
“When I first started, everybody had their secrets about how to do things. That was before the internet,” she says. “Now, you can learn anything via the internet or brokers or breeders. The information is more accessible than it’s ever been.”
In addition to sharing her knowledge directly with apprentices, Oldfield also gives them access to other training resources, such as industry trade magazines, webinars and conferences. She even coordinates local field trips for her growing team to tour nearby greenhouses.
“We have some great competitors around us, so we’ll take a field trip to show [our team] another operation,” she says. “They’re very welcoming and there’s no secrets anymore. Some of them even feed us lunch! If they want to bring their people here, we reciprocate.”
Oldfield has experienced this friendly willingness to help throughout the industry and she’s grateful to have connections with growers across the country who are quick to share advice.
“Everybody’s very accessible. I can call two or three people and say, ‘Have you had this issue? What did you do?’” she says. “It just makes life easier.”
Oldfield enjoys the challenge of growing and even though the days are busy and the hours are long, she finds her job rewarding — even peaceful at times.
“I get in early in the morning and it’s calm and quiet and beautiful. I get to walk through and see all the color every day,” she says. “It doesn’t feel like a job most of the time. It does get crazy, but it’s very rewarding to see something start to finish.”
Even so, Oldfield notices that it’s getting harder to find help. Growers like her aren’t just waiting across the street for opportunity to knock. Although she’s not planning to retire anytime soon, she feels lucky to have her replacement already lined up. She’s excited about the future job potential in this industry for those with the initiative to take it.
“The demand is there for growers,” she says, “so if you want to put in the time, the opportunities are endless.”
The author is a freelance writer and frequent contributor to Greenhouse Management magazine.