Selecting energy/shade/blackout screen materials
Departments - Tech Solutions
Choosing the right material can be difficult, but can be done based on a grower’s needs.
Over 100 types of screen materials are available. This example has alternating aluminum and clear strips that reduce heat loss and provide summer shade.
Photos courtesy of John W. Bartok Jr.
Since the 1970s energy crisis, screens have become an important part of environment control in greenhouses. More than a hundred types of fabrics have been developed for different purposes and all of them provide some energy conservation. They can be fully transparent to completely opaque, have open or closed weave, have reflective surfaces to reduce radiation or provide blackout conditions. Depending on the desired environment, selecting the right one can be difficult.
Comparing materials for energy conservation and other properties has also been difficult, as there have not been any standard tests available. In the past, most of the reported energy savings are from evaluating fuel savings in a particular greenhouse.
Recently, a standard in the Netherlands has been developed to provide uniform testing (NEN 2675 – 2018). Some of the properties that they examine include the following:
Energy savings – 30%-35% of total greenhouse heat energy is infrared thermal radiation. Energy screens reflect part of this heat (emissivity) from the surface. Screens also transmit radiation (transmissivity) through the fabric. The best screens are those that have a low emissivity and a low transmissivity. Screens with aluminized surfaces or aluminum strips meet this criteria and have the lowest radiation loses. Generally, if you install a single screen for energy conservation, select one with a closed weave and aluminum strips (Svensson – Tempa). This will provide shading during the day and energy conservation at night. Cracking the screen sections a few inches wide during the day will allow excess moisture to escape through roof vents.
Plant cooling: In hot climates, shading is important both for plant and air temperature control. In this situation, an open weave material works best (Svensson – Solaro, Polysack Plastic Industries – Aluminet). It allows the heat to rise and escape out through roof vents. It also allows the heat in the moisture to escape. The aluminum or white platic strips reflect the heat before it reaches the plant area. Depending on the amount of strips, it can provide moderate energy savings. An outdoor version of this material can be installed above the greenhouse to keep the heat from reaching inside.
Tears and flaking of the aluminum coating and gaps (as shown here) reduces the effect of screen material.
Winter light transmission: To reduce heat loss during the daytime during the winter, a use of a material having a closed weave and high light transmission could be used (Svensson – Luxous). Materials with light transmission as high as 89% are available. Multiple screens of this material are sometimes installed to control the light level depending on the cloud cover.
Light Diffusion: Diffused light penetrates deeper and more uniformly into the lower plant leaf surfaces. It can increase growth and yield on most plants, especially tall ones, and is most effective on taller climbing crops, such as tomatoes, cucumbers and roses. Diffuse light can also reduce scorching, lower container temperature, reduce fungal spores and decrease insect propagation. Scattered light can also change the balance between red and far-red light. Alternating white and clear strips provides both energy conservation and uniform light across the growing area (Svensson – Harmony).
Blackout: To provide photoperiodic control for sensitive plants, a blackout material is needed ( Svensson – Obscura). It is available laminated with white surfaces on both sides to reflect summer heat away from the greenhouse and reflect supplemental light back to the crop area. With an inside aluminum surface, it will provide 70% energy savings.
Multiple screens are becoming popular to get maximum energy conservation. Cost is on average between $2 - $5/sq ft installed.
Most screen materials are available in many shade levels and energy conservation percentages.
A material that is flame retardant will meet most building codes.
To reduce the shading when retracted, select a material that folds compactly.
To be effective all screens should have a tight seal where they butt against the greenhouse wall and trusses.
Useful life of the material is 5 – 10 years. System life varies up to 20 years.
Clean dust and dirt to retain high light transmission, replace when it is frayed or aluminum delaminates.
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
Departments - Meet the Grower: Bob Glover
Head grower Bob Glover applies business leadership skills in the greenhouse to cultivate his team.
Robert "Bob" Glover worked his way up from a part-time side job watering plants to the head grower role.
Photos courtesy of Robert Glover
Growing up, Robert “Bob” Glover wanted to be a weatherman. Now, he deals with the weather every day as head grower at Dan Schantz Farm & Greenhouses.
Blending his love of science with his strong business background, Glover uncovered the perfect opportunity to grow his career in the greenhouse industry.
“I never expected to be doing this, but I like the challenge,” says Glover, who studied meteorology at Northwest Missouri State University. Facing tough competition for meteorology jobs out of college, Glover took a sales job with intentions of working in business briefly before returning to the weather industry.
Glover ended up staying in business, managing several retail operations over the next 17 years. Then, he bought a house — and everything changed. Especially after he began landscaping around his home.
“It clicked with me almost immediately, just sticking my hands in the dirt,” he says. “I loved everything about it — how the plants looked, watching them grow — and I became a plant nerd pretty quickly.”
Glover became well-known in the neighborhood for his houses’ colorful curb appeal. Some friends, who worked at a local greenhouse, heard about his green thumb and asked if he wanted to work with them. What started as a side job watering plants in 2009 soon evolved into a full-time role, as Glover earned promotions to assistant grower and, eventually, head grower at Ritter Greenhouse in St. Louis, Missouri. As much as Glover enjoys growing plants, his experience and passion for managing people is what makes him so successful in this role. “My strength is leading people and training them to become better than me,” says Glover, who moved to Dan Schantz Farm & Greenhouses in 2019. “That’s what I learned from business: To be successful takes more than numbers. It’s about the people, because they are the ones who are going to make the numbers happen and make the plants beautiful.”
Without any formal training in botany or horticulture, Glover absorbed his greenhouse know-how through on-the-job training. The team at Ritter taught him technical plant knowledge as well as the “intangible intuition” of growing, he says. Now, his goal as head grower is passing that wisdom down to the next generation — which currently consists of four growers and one assistant grower, and he plans to add more roles next year.
“I try to teach them, not only the technical side of growing, but also the leadership skills they need to succeed; that’s even more crucial,” Glover says. “I try to train them to be a step ahead of where they’re at, so if something happens or someone leaves, they’re ready to jump into the next position.”
Glover instills a sense of ownership in his growers by making them responsible for maintaining their respective sections with pride, as if it were their own property. Meanwhile, he looks for teachable moments that allow growers to learn from each other.
“When I see new issues in the greenhouse, I’ll bring the whole staff in to take a look at it,” Glover says. “I explain to them what it is, why it happens, and how to respond. Outbreaks of pests or bacteria can add some pressure when you’re dealing with a live product, so what do you do in a situation like that?”
Glover enjoys mentoring the growers and plant enthusiasts of tomorrow whenever he can.
Glover gets excited when he discovers a new bug or unfamiliar pathogen in the greenhouse because he enjoys the problem-solving challenge. Of course, he doesn’t claim to have all the answers for every plant issue, so he often turns to his network for help.
In fact, the biggest contrast he’s noticed in the green industry, compared to the competitive retail world he cut his teeth in, is how helpful his growing peers have been. “The greenhouse industry tends to be more tight-knit,” he says. “Even competitors will give you a helping hand. That’s very different from what I saw in previous businesses.”
Glover sometimes calls Ritter to ask his former team for advice on how to handle certain diseases. He routinely reaches out to his vendor reps for ongoing support, as well — especially as he adjusts to the climate conditions in Pennsylvania after nearly a decade of growing in Missouri.
“As a head grower, you just can’t do it all by yourself. You’re only as good as the people around you, so it’s good to have a network of people who are smarter than you." - Robert "Bob" Glover
“Growing in the Northeast is a lot different than growing in the Midwest, so it’s good to have a network that’s used to growing in this environment,” says Glover, who oversees 504,000 square feet of covered production — and just as much space outside — where his team grows bedding plants, annuals, bulbs, mums and poinsettias.
By leaning on his network and building his internal staff, Glover takes a team approach to solving problems and improving efficiencies at Dan Schantz Farm & Greenhouses.
“As a head grower, you just can’t do it all by yourself,” he says. “You’re only as good as the people around you, so it’s good to have a network of people who are smarter than you.”
The author is a freelance writer based in Cleveland.
The rise of rare
Departments - Hort Truths
Consumer plant preferences are evolving beyond the basic and towards the exotic and rare-to-find varieties. Read on for tips for successfully serving these new plant parents.
March 22, 2021
Photo © Pixel-Shot, © ottochka, © coolnina | adobe stock
Specialty and rare houseplants are seriously hot right now, with new plant parents shelling out serious green for their new foliage friends. Many customers are turning to small specialty or hobbyist growers to find the species they want, because they cannot find them at their local garden center or plant shop.
While most retailers are good at stocking the common houseplants, these species are not doing it anymore for plant parents who have graduated beyond beginner basics. If, as a grower, you are willing to take on production of some more hard to find species and cultivars, you could open big houseplant opportunities for your retailers and your bottom line.
As I write this column, I am teaching an elective winter quarter course for UCLA Extension called “Indoor Plants: Care and Maintenance”. Many of my students are enrolled in the Horticulture and Landscape Architecture Certificate programs at UCLA Extension, along with several architecture and interior design students.
What I am learning from my students is that in addition to rabid rare plant collectors, there is no shortage of new indoor plant enthusiasts coming into the pipeline. Plenty of plant-y people are looking for commonly available snake plant, Pothos ivy, peace lily, Hoya spp. and the like. If you are well stocked on the common top 10 houseplants, you still have a healthy market to serve for your local independent garden center and plant shop retailers. Yet, many indoor plant keepers who dug into the hobby in the last few years, or perhaps last spring at the start of the pandemic shutdowns, need to feed their desire to increase and diversify their plant collections.
Rarity is the game
For these customers, possession is the passion. The spirit of plant collecting is, or already has, come back with a rage. Aroids are of course getting the bulk of attention from new plant parents right now, as it is tough to resist their lush leaf forms and striking variegation. Prices for tiny pieces of the variegated cultivars of Monstera deliciosa are going for what I even feel are ridiculous prices. This Monsteramania, as I call it, has driven many small growers to the auction block with their plants and pulled many inexperienced hobbyist growers into the marketplace. Beyond Monstera spp., Alocasia and Anthurium spp. are picking up major steam.
Anytime I am writing about houseplant trends, I always check in with my friend Maria Failla of the Bloom and Grow Radio podcast, who also happens to be one of my Indoor Plants students. Her community of plant parents offers a unique window into the mindset of the new indoor gardener. “The rise of rare plants is obviously very real” says Failla. “I’ve heard of people keeping computer tabs open with the online shops on rare plant sellers and refreshing the sites all day to make sure they don’t miss any ‘drops.’ Rare aroids seem to be the hottest commodity (with people paying hundreds of dollars for a mere leafless node of a variegated Monstera).” She offers up that there is also a lot of talk about rare Hoya and she’s still seeing a demand for Philodendron ‘Pink Princess’.
The lengths some customers are willing to go to in pursuit of securing a desired aroid specimen is admirable, but not always advisable. One important observation I will pass on is that there are many indoor plant beginners biting off way more than they can chew with many of the rare aroids.
We know that the highly variegated types of Monstera are not the easiest plants to grow, especially for beginners who no doubt have far too little light in their apartments to serve such plants. Alocasia and Anthurium spp. can be tricky when it comes to changing seasonal and growing media requirements.
When an inexperienced customer pays more than they probably should for a species that is beyond their experience, failure and disappointment ensue. This does not bode well for the longevity of their hobby or their lifetime value as a customer. For starters, price backlash is starting to become an issue. Not to mention, many of the newer small hobbyist growers play far too fast and loose with disease and pest control, simply due to lack of knowledge and experience.
Commodities aren’t cool
The Catch-22 with the rabid rare plant collectors these days is that the moment a popular rare species becomes more prevalent in the market, it immediately falls out of fashion. These plant parents have no interest in anything perceived as a commodity.
If you are a small grower, you may have the flexibility to grow small lots of a wide variety of species, and shift production quickly on trends for rare plant collectors.
Larger growers? Take your cue from rare plant trends, then grow and market to the beginning and intermediate market of plant parent who are willing to grow anything that has an interesting form.
One recommendation I will make is that we need a more diverse selection of easy to grow aroids. Where larger growers can fill an important void for garden centers and plant shops is with clean-grown species that are not common in the marketplace, but do not require expert experience to maintain (and ship well to your retailers).
I am thinking some of the more rare but easier to grow Philodendron species and cultivars, such as P. hastatum commonly referred to as silver sword, P. billietiae, or P. ‘McDowell’ a hybrid that looks like a fancier Alocasia. P. melanochrysum was probably the most sought-after Philodendron of 2020, so any species with a similar look. Epipremnum pinnatum ‘Cebu Blue’ is a stunner but easy to grow. Also, offering up some variegated species that also are not so challenging, such as variegated Syngonium ‘White Marble’. These are just a few examples.
Obviously, your capacity to support the rare plant market depends on your individual business model. In the end, it all comes down to targeting the right customer for your business, and managing your marketing messaging accordingly.
Leslie (CPH) owns Halleck Horticultural, LLC, through which she provides horticultural consulting, business and marketing strategy, product development and branding, and content creation for green industry companies. lesliehalleck.com
Controlled-release fertilizers 101
A CRF applied at different rates and applied on different ornamental plants
Photo courtesy of chrisTOPHER J. currey
Providing adequate mineral nutrientS to greenhouse crops is essential to produce healthy, marketable plants that will perform well for consumers. However, managing fertilizers is just one of many tasks growers have to deal with every day.
Water-soluble fertilizer (WSF) is ubiquitous in greenhouse crop production, and for good reasons. Yet controlled-release fertilizer (CRF) can be a great option, either as an alternative to WSF or as a complement in production.
This month’s Production Pointers will cover some of the important considerations for anyone considering CRFs for their crops.
Controlled vs. slow
First, the focus of this article is on controlled-release fertilizer — not slow-release fertilizer (SRF). It is common to hear these names used interchangeably, but they are indeed different. While both CRF and SRF release fertilizer over time, CRF utilizes polymer coatings, as well as additional chemical treatments in some instances, to release nutrients in a controlled fashion. Alternatively, SRFs rely on the breakdown and degradation of their coating to release nutrients.
As with any fertilizer, the analysis states the percentages, by weight, of mineral nutrients in the CRF. Just like with WSF, there are a variety of different complete fertilizers available to choose from, with nitrogen:phosphorous:potassium (N:P:K) ratios ranging from the standard 1:1:1 to those formulations with less P or with greater K. Formulations containing no micronutrients, as well as those with a complete suite of micronutrients, are also available. Be sure to check that what you are purchasing will meet your needs.
Nutrient release from CRFs can vary in time and pattern. First, CRFs are rated in the duration in time of nutrient release — typically in either months or days. There are a wide variety of release durations, from as short as two months up to one year, and they should be matched with the crop they are going to be used for. The release durations stated are based on a specific temperature, and it is important to keep in mind release will be slower or faster at cooler or warmer temperatures, respectively.
In addition to the total release period, there are specific formulations that provide a quicker — or slower — start of release to further accommodate grower needs.
When it comes to prill size for CRFs, one size does not necessarily fit all. In addition to the standard — or “regular” — sized fertilizer prills, manufacturers are producing CRFs in smaller sizes. Pound-for-pound, these micro prills have the same amount of fertilizer as larger prills when analyses are the same. However, the smaller prill has advantages compared to the larger prills in certain situations.
Most importantly, micro prills are well-suited for use in small container sizes to help uniformity in fertilizer distribution across containers. Take, for example, a flat of bedding plants in 1204 packs. Using the same amount of fertilizer, by weight, micro prills would result in a more even distribution of fertilizer across the 48 cells in the flat compared to larger, standard prill sizes.
When it comes to CRFs, it can be useful to “think outside the pot”. We are often considering how CRFs can be used to provide mineral nutrients to containerized crops during production. Yet, there are also opportunities to fertilize plants once they have left the greenhouse.
Although we would like to believe consumers fertilizer their plants, I don’t think any of us are under the illusion this is the reality. When CRFs are used to produce plants in the greenhouse, this can potentially provide additional nutrients to plants after they have been purchased by consumers. For example, if a CRF with a 3-4 month release rate is used for producing herbaceous annual bedding plants in 4-inch containers, the length of the production time in the greenhouse is less than the CRF release period, and essential nutrients will continue to be available for consumers.
Consider a blended approach
Using CRFs is also not an all-or-none proposition. Consider combining CRFs in combination with WSF. Using a low rate of CRF, such as incorporating 1.5 to 3 pounds of CRF per cubic yard of substrate, along with low concentrations of WSF allow you to take advantage of the positive attributes of both CRF and WSF, providing plants with consistent baseline nutrition while still maintaining flexibility in fertilizer programs.
Or, along with WSF, use CRFs to provide more nutrients to those heavy feeding plants in your annual bedding plants program.
Controlled-release fertilizer technology has come a long way, and the CRFs available on the market today provide opportunities to simplify production. Remember that CRFs can also be used as a tool to cater to the needs of specific crops in a diverse greenhouse, and potentially provide benefits to consumers.
Christopher is an associate professor of horticulture in the Department of Horticulture at Iowa State University. firstname.lastname@example.org
Top stories from Greenhouse Management’s website
Departments - Home Page
March 22, 2021
On Monday, Wednesday and Friday of each week, you can get the latest industry news right in your inbox with the Greenhouse Management newsletter, featuring the latest headlines and stories from the magazine. You'll find everything from exclusive research and industry insights to production tips and breaking news. To subscribe to the newsletter, visit bit.ly/greenhouse-newsletter.
Here are some of the top headlines you might have missed.
Photo courtesy of David Torrance
Norwin Heimos dies at age 90
Norwin Heimos, the founder of N.G. Heimos Greenhouses and Millstadt Young Plants in Millstadt, Illinois, died on Feb. 18. He was 90.
Heimos founded the company in 1951 as a fruit and vegetable producer and the first greenhouses were built in 1955. The Millstadt facility was acquired in the mid-1980s. Three generations of his family have led and continue to lead the business, including his daughter Amy Morris and grandson Adam Heimos.
Read more at bit.ly/3riWMct
Botany Lane Greenhouse obtains Veriflora certification
Per a press release, Botany Lane has been certified by Veriflora Sustainably Grown by “meeting the highest levels of performance under the three internally recognized pillars of sustainability: environmental stewardship, social responsibility and economic stability.”
“We are very proud of this certification as it validates all the hard work we are doing as a company to align our practices with the Veriflora standards to keep us focused on sustainability within our community,” said Scott Fulton, general manager at Botany Lane, per the release.
Read more at bit.ly/2MLVNlY
Dümmen Orange debuts ‘Norwin’ poinsettia
Dümmen Orange, per a press release, has announced that it will be honoring the legendary horticultural leader Norwin Heimos, who recently passed away, with the new ‘Norwin’ poinsettia.
An instrumental collaborator with the Ecke poinsettia program (now part of Dümmen Orange), Norwin found a new pink genetic sport of a poinsettia in 1994 which was later named V-14. He brought it to Ecke and this variety was the new industry standard for years in pink poinsettias with the deepest color at the time. It was successfully sold worldwide from 1996 to 2004.
The ‘Norwin’ poinsettia, per the company, is an improvement in orange color and provides color very early in the season, enabling growers to offer it in time for Thanksgiving. It will be introduced for the 2022 holiday season.
Read more at bit.ly/3e9d6IV