Light is one of the key components needed for growing plants. A rule of thumb is “1% increase in light equals 1% increase in plant growth.” How can we increase the light level, especially during the dark days of winter?

Research has shown that greenhouse film and polycarbonate lose 2% or more light transmittance each year because of ultraviolet light. Depending on where your greenhouse is located, dust, dirt and air pollutant accumulation may also cause light reduction. A 5% reduction per year is likely in some areas near large cities on the east coast, Midwest or west coast. Industrial areas also tend to have greater smog (smoky fog) concentrations.

I recently visited Freund’s Farm Market and Bakery in East Canaan, Connecticut, to do an energy audit. Theresa Freund indicated that they had replaced the 20-year-old polycarbonate on their 7,200 sq. ft. gutter-connect greenhouse. She found this resulted in having to rework the plant production schedules as the increased light reduced the plant production time in the spring by two to three weeks.

New glazing can reduCe the heating cost

A simple calculation can be made to estimate the fuel savings for the reduced time when the greenhouse is not heated. Determine the heating degree days for the year. This can be calculated from degree day data available for any location in the world on the website www.degreedays.net. Based on research at Rutgers University, select a temperature that is 50 less than the night operating temperature and let the program calculate the number of degree days. Solar energy makes up the 50 difference. Divide the estimated gallons of oil or propane or ccf of natural gas used for that greenhouse for the year by the number of degree days to get the fuel use/degree day. From the degree day calculations, determine the number of degree days during the period when heat is not needed and multiply by the fuel use/degree day. Then multiply by the cost of the fuel to get the savings.

The Freund’s Farm greenhouse used 3,880 gallons of propane for 1,400 degree days for the year 2020, or 2.77 gallons/degree day. There were 400 degree days in the first two weeks in March when the greenhouse didn’t have to be heated, resulting in 1,108 gallons being saved. At $3/gallon propane, the savings for not having to provide heat resulted in a savings of about $3,324. This helps to offset the cost of the new glazing. There is also a savings in labor not needed to maintain the plants for two weeks.

For air inflated greenhouses, replacing the plastic yearly may be economical. During the summer, light levels are high enough that the reduction in light may not affect plant growth. It is during the late fall, winter and early spring when this is of most concern. Let’s look at an example. The cost of replacing the double layer of plastic on a 30’ x 100’ hoop house is about $1,500 ($0.50/sq ft for plastic and labor x 3,000 sq ft = $1,500). It would take an increase in production of just 0.63 lb/plant of tomatoes at a wholesale price of $3/lb to pay for the new plastic. Increased yields of one pound/plant or more are not uncommon when new plastic is installed.

Now that we have taken care of the easy upgrade to the greenhouse, let’s look at some other areas where light getting to the plants could be increased.

Inside the greenhouse

• Place water, heat pipes and conduits below ground, along the post line under the gutter or along the sidewalls.
• Install energy/shade screens that retract into a small space. When retracted, some shade systems create more than 10% shade.
• Locate overhead heaters near the north wall of the greenhouse when possible.
• Use a glazed louver system rather than motorized metal shutters.
• Remove insect screening and evaporative pads during the winter.
• Remove overhead hanging basket supports for the winter. Eight rows of 1-1/4” support pipe create more than 5% shade in a 21’ bay.
• Paint structural members, bench surfaces and walkways white to reflect light. White paint will give about 80% reflection, whereas aluminum reflects about 60% of the light that strikes it.

Outside the greenhouse

• Remove all remnants of shading and grime from the glazing before winter. Use shade remover or a power washer.
• Remove nearby trees if they create shadows on the greenhouse. Observe the shadows during January and February.
• Purchase a light meter and check your greenhouses for light transmittance. A few changes may increase light levels significantly.

Have you been feeling a little black and blue the last couple of years? Me too. So, I decided “bruised” would make a fitting garden color scheme theme for 2022. “Bruised” has always been my favorite color combo, but it feels particularly appropriate right now. Black, blue, purple and a bit of chartreuse thrown in for contrast and accuracy. As luck would have it, there are some lovely black and blue perennials hitting the retail market in 2022.

Dark times

Dark times often seem to call for dark foliage. The black foliage plant trend isn’t new, but we’ve seen a resurgence in its popularity over the last year or so, especially in the houseplant market. The Raven ZZ plant, Alocasia, Peperomia, Begonia, and jewel orchids (Ludisia discolor), sparked much of the excitement in the indoor garden. Taking your cue from indoor gardening trends, black foliage will also resonate with your outdoor gardeners.

Consumers are simply trying to find something different or unique to enhance both their living spaces and gardens. Black, or almost-black, foliage and flowers certainly deliver on distinction. Given the number of new perennial plant releases that look to encourage gardeners to grow to the dark side, I’d say black foliage is due for another moment in the sun.

I did manage to make it on one business trip scheduled over the last two years that didn’t get cancelled: AmericanHort’s Cultivate ’21 show. While it felt a bit strange (I suspect not only for me) figuring out how to navigate a crowded convention center during a pandemic, I made a few fast passes through the trade show floor; specifically, to hunt for new standout plant varieties.

The new perennial releases that caught my eye include:

Sedum ‘Back in Black’: You can definitely go to the dark side of your sun garden with this fall-bloomer. Near-black leaves will offer standout contrast in your garden most of the growing season, followed by flowers with cream petals and a bullseye red center, creating a pinkish hue across the bloom clusters. Give plants full sun to retain the rich and deep foliage color.

Hibiscus ‘Edge of Night’: While pink flowers don’t technically fit into my “bruise” color scheme, there’s no denying that the foliage of this new compact hardy hibiscus are near-black and quite stunning. The foliage is described as “jet black,” which does make a lovely contrast to the huge 8-inch rosy, pink flowers. With plants growing to only 3-3 ½ feet tall, this cultivar should make a nice container specimen as well. Full sun, of course, keeps these beauties in full flower and foliage intensity.

Got the blues?

Geranium ‘Boom Chocolatta’: As its name implies, this gorgeous Geranium pratense hybrid has deliciously dark bronze foliage with chocolatey tones. But it’s the combination with intense purple-to-blue flowers that place this plant firmly into my bruise-appropriate scheme. While I believe this cultivar first hit the market a couple of years ago, this is the first I’m seeing of it, and it is a new intro in the Proven Winners Perennials program. Now, down here where I garden in Texas, I can’t say we have a ton of luck with cultivated cranesbills due to our extreme heat and drought; but when planted here, they are best positioned in a dappled shade garden. I’m certainly willing, given its promise to be more “vigorous,” to give it a try in my tough Texas garden.

Schizachyrium scoparium ‘The Blues’: This little bluestem has earned itself the coveted Perennial Plant of the Year designation for 2022, and for good reason. This tough clumping grass sports the most ethereal ice blue foliage, accented by red stems. As fall temperatures cool, each plant takes on its own “bruised” stem, offering a mix of colors from purple to blue to orange. The beauty of this blue stunner is that it thrives in poor soil and limited water. It’s an easy-to-grow water-wise perennial in full sun locations, if you’re willing to forego any extra TLC.

Amsonia ‘String Theory’: The light blue to periwinkle flowers sported by this compact cultivar look like tiny stars sprinkled over your garden. If you’re looking for a more compact and denser alternative to Amsonia hubrichtii, with the bloom power of A. tabernaemontana ‘Storm Cloud,’ ‘String Theory’ promises to deliver. It also promises to deliver dark green foliage all season long, instead of the chlorotic foliage so often present in the standard species. At only 18-22” tall, this compact blue beauty can move to the front of the border.

Purple punch

No bruise would be complete without a punch of purple in the mix. One of my favorite finds at Cultivate ’21 was the new Cake Pops line of tuberous Verbena rigida, with purple clearly a standout color-wise. This is a species that is quite at home in my tough Texas gardening climate, but it can become a bit of a beast. So, I was excited to spot these cute round mounds of compact Cake Pops in containers in the New Varieties area of the show. The compact mounded form lends them to both the front of the border and containers — not to mention hanging baskets. Hey, a V. rigida hybrid might be one of the few things that can survive a Texas summer in a hanging basket without 24/7 irrigation. I’m here for it. OK, I realize that as far as the Zone 5 Mafia is concerned, this plant is an annual. But, for the entire southern half of the country, this species is happy to stick around year after year.

Lest you worry I’ve forgotten the disconcerting chartreuse colors that often make for a good shiner, I encourage you to check out the new and intriguing Jurassic Fern series, all of which look to offer up yellow-green to chartreuse foliage colors, perfect for bruisy contrast in the shade garden.

My advice for 2022? Just make sure to keep a few bags of frozen peas handy.

Logos courtesy of respective companies

All-America Selections announces the 2021 winner of the America in Bloom/All-America Selections Showcase Garden Contest

All-America Selections (AAS) announced Gloucester, Massachusetts as the 2021 winning community in their America in Bloom/All-America Selections (AIB/AAS) Showcase Garden contest.

In early 2021, twenty AIB participating communities were offered the opportunity to plant an AAS Showcase Garden. The number of 20 gardens was chosen to celebrate America in Bloom’s 20th Anniversary in 2021. Each community received a minimum of twelve zone-appropriate AAS Winner varieties at no cost to their communities.

The community’s gardens must be on public display with all plants labeled with variety names.

Tim Lauer named president of the National Greenhouse Manufacturers Association

The National Greenhouse Manufacturers Association (NGMA) has announced that Tim Lauer, of Albert J. Lauer, Inc. in Farmington, Minnesota, has been named the new president of NGMA’s Board of Directors. He assumed the role after Tom Vezdos stepped down from the position.

Lauer brings over 26 years’ experience in the greenhouse industry. He is proudly the third generation following in his father’s and grandfather’s footsteps. His grandfather founded Albert J. Lauer, Inc. in 1947; and Tim, as the company’s vice president, continues designing, manufacturing and building aluminum greenhouses for commercial growers, retail garden centers and institutional markets today. Being a member of NGMA for many years, Tim most values the opportunity to learn, discuss, collaborate and network with other business owners, engineers and designers.

Kate Santos joins Longwood Gardens

Per a press release, Longwood Gardens has appointed Kate Santos, Ph.D., as Director of Research and Conservation. She will lead the “organization’s science-based activities, strategically driving excellence in research, conservation, land stewardship and ecology with local, national and global impact.”

Santos joins Longwood with 15 years of experience leading for-profit business functions in horticulture. Most recently, she founded Kate Santos LLC, a botanical consulting firm, bringing solutions to the world’s most growth-oriented horticultural companies.

Before that, Santos spent six years at Dümmen Orange, where she served as North America operations director and regional director of supply chain for the Americas, managing leadership teams across North America, Central America and South America. Santos also spent time working in research at Costa Farms in Miami, Florida.

Watering greenhouse crops is arguably one of the most important tasks at any production facility. How and when crops are irrigated affects plant growth and development, and ultimately, finished plant quality.

Irrigation also affects other aspects of production, such as plant diseases, and water- and nutrient-use efficiency. The manner in which crops are watered also can have a large impact on labor costs. There are a variety of ways to irrigate greenhouse crops, and this article is going to focus on subirrigation and some of the tips and tricks or best management practices to keep in mind.

Overhead irrigation, where water and nutrient solutions are delivered by hand with a hose or automated from a boom, is the most common form of irrigation.

Drip tubes or drip emitters irrigate on the surface of the substrate, and are also widely used. Subirrigation is a technique where water or nutrient solution is provided to the bottom of the container and is absorbed or taken-up into the growing substrate by capillary action. There are a number of different methods of subirrigating plants, including ebb-and-flood benches or Dutch trays, flood floors, or capillary mats.

While these different subirrigation systems vary in their cost and lifespan, providing options for any scale of production, the principles of using any subirrigation system remain the same for all of them.

Why use subirrigation for growing greenhouse crops? There are a few advantages to taking this approach. First, subirrigation can help minimize diseases, specifically foliar diseases. High humidity and free-standing water promote diseases such as botrytis and powdery mildew. Overhead irrigation leaves foliage wet, and drying is promoted by watering early in the day and allowing sufficient time for foliage to dry, as well as through the use of horizontal air flow (HAF) fans. With subirrigation, foliage stays dry regardless of irrigation. Subirrigation also allows for more flexibility in timing irrigation — watering crops later in the day won’t run the risk of wet foliage going into in the evening.

Aside from minimizing foliar diseases, subirrigation can improve plant quality. As previously mentioned, water or nutrient solution is taken up by capillary action in the root zone until the substrate is saturated. Compared to overhead irrigation, where the same, or a similar, amount of water is applied to each container regardless of how wet or dry it is, subirrigation allows containers to absorb varying amounts of water until they reach the same saturated level, improving uniformity across the crop.

Subirrigation is also flexible and accommodating for different crop spacing. Whether it is shuttle trays of 4-inch containers placed pot tight or 8-inch poinsettias on 18-inch centers, it doesn’t matter for subirrigation. This flexibility makes the switch between crops throughout the year seamless and easy, especially when compared to using drip tubes and emitters that have fixed spacing.

Finally, like any form of automated irrigation, labor savings can be significant for subirrigation systems. By eliminating hand watering, subirrigation allows for hundreds to thousands of plants to be irrigated at the same time, depending on the size of the subirrigation zone.

There are some cultural practices that will have to be modified or monitored carefully when using subirrigation, regardless of which system is used. First, fertilizer concentrations have to be reduced. Whether it is water-soluble or controlled-release fertilizer, less is required with subirrigation. Since water moves up into the container through capillary action, there is virtually no leaching when crops are subirrigated.

Although this can be considered a good thing, especially to improve water- and nutrient-use efficiency and avoid unwanted runoff, there is no opportunity to leach excess fertilizer salts out of containers and reduce electrical conductivity. Using less fertilizer will help avoid supra-optimal substrate ECs and still provide sufficient nutrients for plant growth. By how much should fertilizer concentrations be reduced? A good place to start is to reduce concentrations by 50% compared to what would be used in overhead irrigation. When in doubt, err on the side of less fertilizer. Plants can always be provided with higher concentrations of water soluble fertilizer (WSF) to increase substrate EC in subirrigated systems, but providing too much may be challenging to deal with.

Another consideration for subirrigated systems, especially those that are capturing and recirculating water and nutrient solutions, is excess pesticide runoff, including plant growth regulators (PGRs), insecticides and fungicides. When these solutions have the potential to be recaptured in the same reservoir where water and nutrient solution is stored, the active ingredients can be taken up during subsequent irrigation events. Ultimately this can lead to unwanted and/or excessive applications of these chemicals. When drench applications are made to containers grown in subirrigated systems, try to minimize any leaching of pesticide solutions out of the container. Similarly, avoid excessive runoff from canopies and applications to floor or bench areas.

Finally, sanitation should be a priority in any subirrigation system. While greenhouse sanitation is important for any operation, regardless of their irrigation system, it takes on additional importance for subirrigation systems where water and nutrient solutions are captured and reused. Diseases are generally not going to be transmitted plant-to-plant via transmission in subirrigation systems, as the water is taken up by the substrate and no leaching occurs. However, if pathogens are introduced into the water from other means, such as infected plant materials laying on the bench or floor, then infested water that is recirculated and provided to plants can cause diseases to spread quickly.

Maximizing crop quality and minimizing labor are common goals for any greenhouse grower. Regardless of what scale you are producing on, there are subirrigation strategies that can fit your facility and budget. The best management practices outlined in this article can help deliver optimal results with subirrigation systems.