Editor’s Note: In this third article from a five-part series on potted and hydroponic culinary herb research at Michigan State University, researchers share the results of several studies showing how you can inhibit or promote flowering.

An issue that culinary herb growers face is the inability to keep crops vegetative as both retailers and customers often demand non-flowering, fresh-cut leafy greens and culinary herbs. For producers, flowering of culinary herbs such as basil, cilantro, mint, oregano and watercress is usually undesirable, since vegetative growth can stall once flower initiation occurs. Additionally, once herbs become reproductive, flavors can be altered and less appealing to consumers.

Alternatively, flower induction protocols are lacking for herbs such as basil and lavender that are marketed for ornamental purposes as bedding plants or cut flowers, or for those used in the production of essential oils. In these cases, flowers are desired as consumers are more likely to purchase a flowering ornamental or cut flower herb arrangement, and aromatic oil concentrations are maximized when plants are in flower.

Greenhouse growers of floriculture crops often delay or promote flowering by manipulating the photoperiod (day length), temperature or the cumulative amount of light that a plant receives over the course of a day (the daily light integral). For example, the day length in a greenhouse can be easily modified by creating short day (SD) lengths during naturally long days (LD); or by creating LD lengths during naturally SDs.

To create SDs, light-blocking opaque black cloths are pulled over plants to shorten the natural day length and artificially create a SD. Low-intensity photoperiodic lighting providing 2 to 3 µmol·m–2·s–1 is most often used to create LDs. It can be delivered in one of two ways: 1) at the end or beginning of the day to extended the day (day-extension lighting), or 2) during the middle of the night from 10 p.m. to 2 a.m. (night-interruption lighting).

In addition to photoperiod, some plants can exhibit a facultative irradiance response (FIR) where they flower faster as a result of the juvenile stage of development being shortened under higher DLIs. Plants exhibiting a FIR develop fewer leaves or nodes below the first open flower than those grown under lower DLIs.

Although some studies have been conducted to determine what environmental factors induce some common culinary and ornamental herbs and leafy greens into flower, the critical photoperiod of new cultivars and many other genera have not yet been determined. Therefore, our goal was 1) to determine if photoperiod and/or DLI influence flower initiation and development of culinary and ornamental herbs and leafy greens and 2) to identify the critical photoperiod that induce flowering of those crops that response to day length.

The study

Cuttings of spearmint ‘Spanish’ were harvested and rooted utilizing protocols outlined in our first article in this series. Seeds of Greek basil (Ocimum minimum ‘Pluto’), holy basil (O. tenuiflorum), lemon basil (O. ×citriodorum ‘Lime’), purple basil (O. basilicum ‘Red Ruben’), sweet basil (O. basilicum ‘Cinnamon’, ‘Genovese’, ‘Nufar’ and ‘Sweet Dani Lemon’), and Thai basil (O. basilicum var. thrysiflora ‘Sweet Thai’), oregano ‘Kirigami’ and ‘Greek,’ lavender ‘Bandera Pink,’ coriander ‘Santo,’ dill ‘Bouquet,’ watercress and marjoram were sown into 128-cell plug trays.

After germination, seedlings were thinned to one plant per cell. The seedlings or rooted cuttings were subsequently transplanted into 4.5- or 6-inch pots filled with a peat and perlite substrate. Basil was grown in a greenhouse with an air average daily temperature (ADT) of 75º F (24º C) and under DLIs of 7, 13, or 23 mol·m^–2·d^–1. All other culinary herbs were grown at an air ADT of 68º F and DLI of 10 mol·m^–2·d^–1.

Each day, black cloth was pulled over individual benches at 5 p.m. and opened at 8 a.m. to create a 9-hour (9-h) SD photoperiod. Treatments consisted of a 9-h SD or a 9-h SD with day extension lighting from four light-emitting diodes (LEDs) providing 2 to 3 µmol·m^–2·s^–1 of red:white:far-red light on each bench to create a 11, 12, 13, 14, 15 or 16-h photoperiods or a 4-h night interruption from 10 p.m. to 2 a.m.

What did we find?

Time to first visible bud occurred more rapidly under LD photoperiods (=13 h) for coriander, dill, lavender and marjoram. The node number under the first open flower was greater under a 9-h SD for coriander, dill, lavender and marjoram, and generally decreased as day length increased to 16 h or under a 4-h night interruption (see Figures 1 and 2). Time to flower of Sweet ‘Nufar’, purple, and Thai basil, coriander ‘Santo’, lavender ‘Bandera Pink’, dill ‘Bouquet’ and marjoram was hastened under LDs, but they eventually flowered under SDs (see Figure 3). Therefore, these herbs were classified as facultative LD plants. After 20 weeks, nearly all dill and coriander plants flowered regardless of photoperiod. However, when grown under a 9-h SD, dill and coriander were more much more compact at first open flower in comparison to plants grown under LD photoperiods =13 h (see Figure 1).

Flowering of sweet basil (‘Genovese’, ‘Cinnamon’ and ‘Sweet Dani Lemon’), lemon and Greek basil was not influenced by photoperiod and were classified as day neutral plants. Lastly, holy and lemon basil, and ‘Nufar’ flowered faster under high DLIs (>20 mol·m^–2·d^–1), compared to under moderate DLIs (>10 mol·m^–2·d^–1) and were classified as having FIR (see Figure 3).

Watercress and oregano ‘Kirigami’ only produced visible buds and open flowers under LD photoperiods =13-h (see Figure 4). Oregano ‘Greek’ and spearmint only produced visible buds and flowered under a 16-h photoperiod or a 4-h night interruption (see Figure 5). These herbs were classified as obligate LD plants, requiring =13-h, =14-h, and 16, or night interruption lighting, respectively, for visible bud initiation and flowering to occur.

Grower recommendations

Grow the following culinary herbs under short day lengths of =12 h to prevent or delay flowering:

• Coriander ‘Santo’
• Dill ‘Bouquet’
• Marjoram
• Oregano ‘Greek’ and ‘Kirigami’
• Spearmint ‘Spanish’
• Sweet ‘Nufar’, purple, and Thai basil
• Watercress

Grow the following culinary herbs under low to moderate DLIs of 7 to 15 mol·m^–2·d^–1 to delay flowering:

• Holy and lemon basil
• Basil ‘Nufar’

Grow the following ornamental herbs under long day lengths of =14 h or a 4-h night interruption to induce flowering:

• Lavender ‘Bandera Pink’
• Oregano ‘Greek’ ‘Kirigami’

It is important to remember that the day length provided during the young plant stage can influence flowering responses. Additionally, production temperatures and DLIs can also impact flowering of culinary herbs.

Charlie Garcia was a M.S. student at Michigan State University and Roberto Lopez is an Associate Professor and Controlled Environment/Floriculture Extension Specialist in the Department of Horticulture at MSU. The authors gratefully acknowledge Caleb Spall for assistance, Signify for LEDs, JR Peters and The Blackmore Co. for fertilizer, The Fred C. Gloeckner Foundation and MSU AgBioResearch Project GREEEN, MSU Graduate School, and the USDA-NIFA for funding.

Spend a few minutes inside Schuyler Greens Company and you’ll notice features uncommon for a growing operation of its size. Beyond the crops of tantalizing leafy greens, you’ll discover automation and technology typically reserved for much larger growers. But time spent talking with founder and farm manager John McMahon reveals the dream that drives this controlled-environment agriculture (CEA) farm. The 20,000-square-foot, state-of-the-art facility is a far cry from McMahon’s beginnings, but this is only the start.

The evolution of farmer and facility

McMahon founded Schuyler Greens Company in 2015 following a successful corporate career, but his agricultural roots reach back to his youth. Raised in western Pennsylvania, he and his siblings learned to tend the family farm while his father, a medical doctor and gentleman farmer, was on call.

After a family move to Virginia, McMahon pursued business degrees and a corporate career that landed him in New York City and Washington, D.C. After more than five years with a near-constant international travel schedule, corporate burnout was building. And McMahon’s lifelong dreams of running his own business stirred.

A rough piece of land near his brother’s Virginia farm caught his eye. Located in Schuyler (pronounced SKY-lur), southwest of Charlottesville, the property soon became the stage for Schuyler Greens Company.

“I built what was probably the smallest greenhouse in history for commercial operators — about 1,500-square feet,” McMahon says. “Basically, I just started very small and learned the business and pounded the pavement and wore all the hats, like every other small business entrepreneur.”

The decision to focus on hydroponic greens came early and easily for McMahon. Talks with potential customers revealed interest in local products, but also concerns about continuity and reliability of supply. With greens, he believed he could overcome those hurdles and supply consistent year-round product for customers — and consistent cash flow for himself.

While the focus on greens stayed constant over the years, McMahon’s business model evolved. He started as wholesale direct to restaurants, then shifted to distributors as capacity increased. Institutional customers such as universities and hospitals followed, as did independent grocery stores.

Today, the Schuyler team consists of McMahon and eight employees split roughly between full- and part-time. “Some like the flexibility of not having full-time work. They want to do a few different things, kind of like the gig economy,” he says.

Despite pandemic pressures, McMahon has been able to maintain production and avoid downsizing. “The last year has been pretty exhausting, but so far, we’ve been able to hang in there,” he says.

Although business in markets such as food service and restaurant sales through distributors are down, grocery store sales are up. And a new Schuyler Greens direct-to-consumer, home delivery e-commerce component has helped.

Currently, the team produces a variety of lettuces, salad greens, herbs and microgreens — plus some mushrooms, too. Products are grown free from traditional chemical pesticides. McMahon relies on organic options, including probiotics and beneficial insects instead. OMRI-listed treatments combine with a mix of organic and synthetic fertilizers used.

A quest for efficiency and sustainability

During five years in business, McMahon has turned to increased automation and technology to run his hydroponic facility more efficiently and profitably. “I’ve done a lot of little upgrades from being pretty hands-on. For our size, we’re super automated,” he says.

“It’s partly having entrepreneurial DNA, but I’m nuts about reading and learning more things. I’m always scouring either university research or industry research or even just general business stuff to get better with production or business and technology to try to be more efficient,” he says.

A strong believer in the benefits of CEA, McMahon feels hydroponic growing allows him to “take it up a level” to meet his growing goals.

“Whatever you’re doing, by controlling your growing environment to some degree, you have more consistent yield, you have better quality crops, and it’s more efficient,” he says. “The goal is to use fewer resources to produce the same or more output. Then also, to be as sustainable or efficient as possible with resources when we produce.”

Cut product, not heads, constitutes most of Schuyler Greens’ product line. With the industry’s migration toward salanova-type and higher-density baby greens, automation from seeding to harvest has been crucial to growth.

McMahon recalls hand seeding arugula in Oasis for his original nutrient film technique (NFT) system. What then took four to five hours — often paired with frustration — now takes 10 minutes with the automated seeding line.

Harvesting is another critical area of automation gains. McMahon still retains some of the NFT system he first launched with, but deep water culture (DWC) production and automated harvesting now dominate.

“We run the baby greens through a harvesting system the rafts go through. That cuts the product versus hand cutting,” he says. “It’s cut our production time compared to our older NFT system. We can produce twice as much in the same time period with less physical labor.”

A switch from high-pressure sodium (HPS) lighting to light-emitting diode (LED) technology also yielded significant gains. Benefits include increased energy savings, reduced HPS-produced heat, and enhanced plant color. “We use a blend of blue and red light spectrum that results in a purplish hue,” McMahon says. “It triggers anthocyanin, so it enables us to have more attractive colors on our plants.”

Regarding return on investment, McMahon says the LEDs have more than paid for themselves: “I’ve seen a lot of positives from them, from a much more attractive crop to lower energy costs.”

Food safety and GAP certifications

From the beginning, McMahon has gone above and beyond the food safety measures one might expect from a grower his size. “I learned what I needed to do, and then as I built up the facility, I put in more features that were conducive to food safety,” he says.

Schuyler Greens Company received U.S. Department of Agriculture GAP (Good Agricultural Practices) certification early on. Food safety auditors wondered why they were testing such a small production facility that obviously couldn’t support the large customers that required the certification. But McMahon had even higher goals.

This year, he took the step to upgrade food safety standards and become USDA Harmonized GAP Certified for Food Safety. The certification was a personal victory for McMahon. He suspects that few end consumers understand the standard operating procedures, controls, checks and documentation H-GAP certification requires, but that wasn’t his goal.

“We have the procedures or protocols in place to really manage food safety and take it seriously. Because to me, we can’t afford to have any food safety issues. I don’t think anyone really can,” he says. “For me, as a business operator and a grower, I can sleep at night knowing we’re doing the best we can possibly do to not cut corners and to reduce our risk profile.”

It’s also good marketing. Regardless of size, the certification clearly sets a grower apart from competitors with less strenuous food safety measures and reassures customers that what they’re buying is safe.

“Customers have no idea what it is. But your institutional buyers and the grocery stores and distributors, they’re all over it,” McMahon says. “Because of the world we live in, it’s a very regulatory-focused industry — especially leafy greens.”

Future plans fueled by innovation

McMahon expects significant changes in the produce industry over the next 10 to 15 years. He believes that plant breeders focused on varieties bred to excel in hydroponic growing environments will augment CEA production’s many benefits.

But, not surprisingly, he envisions dramatic gains in automation and technology that have him looking beyond his greenhouse walls. “Growing is great. I love doing that, but I’d love to try to make a more meaningful impact on the industry, not just my operation,” he says.

He notes that many people he sees rolling out ag technology have never worked in the greenhouse “trenches” or built an operation from the ground floor up. He feels ag tech developers often work in vacuums, lacking firsthand knowledge of grower pain points.

McMahon hopes to put his energies to work on creations to solve growers’ problems and offer greater value and application for CEA. Of particular interest are technologies, software and small-scale automation to help small and midsize growers produce more efficiently without breaking the bank.

“Greenhouses aren’t going away. If anything, there’s only going to be a lot more of them,” he says. “So how do we do things more efficiently and keep pushing the industry forward and keep getting better?” While he’s quick to say there’s no time frame attached to his goal, helping elevate the industry is increasingly on his mind.

For others interested in CEA production, McMahon offers this advice: First, only do it if you’re passionate about it. That goes for any business ventures, he adds. “Know that even though this is high-tech and controlled-environment ag and all those really cool buzzwords, it is a lot of work and it’s still farming. So, make sure you know what you’re getting into,” he says.

Second, he urges would-be and current growers to reach out to mentors, consultants or knowledgeable people and learn all they can. “They can really help shorten the learning curve. I think that’s true in all things in life,” he says. “Learn from people that are more experienced and more knowledgeable than you. I’ve definitely done that here.”

The author is a Minnesota-based freelance writer specializing in horticulture-related industries and a frequent contributor to Produce Grower magazine. Reach her at jolene@jolenehansen.com.

Basil is the most popular culinary herb that is grown in hydroponic systems. For many hydroponic herb growers, basil is the backbone of their program. Growers are usually commenting on how they are able to sell all the basil they produce and can’t grow enough!

However, another comment I hear frequently is how their basil just doesn’t grow in the late fall, winter and early spring. This is when growers are experiencing longer crop times and delayed harvests. Although growth is slower during these “off-seasons,” there are steps that can be taken to increase growth and keep production on track.

When producing cut basil, yield is based on the weight of harvested shoots. Therefore, in order to increase the amount harvested or reduce time until a crop reaches a harvestable size, we want new leaves to appear and mature as quickly as possible. The two factors that are going to have the greatest impact on leaf unfolding and growth are light and temperature.

Temperature

Temperature can affect plants in several different ways. Extremely low or high temperatures can cause damage, reducing yields and/or making shoots unmarketable. Increasing or decreasing the difference between day and night air temperatures (“DIF”) can increase or decrease stem and internode elongation. As previously mentioned, increasing the rate that new leaves are formed can help increase yield. The rate at which new leaves are formed is strongly influenced by the average daily temperature. There are three temperatures that help us understand the effect of average daily temperature on plant development: 1) the base temperature (Tbase), the temperature below which plant development stops, 2) the optimal temperature (Topt), the air temperature at which plant development is maximal, and 3) the maximum temperature (Tmax), the temperature above which plant development stops. Between the Tbase and Topt, plant development has a linear response to average daily temperature and this range of air temperatures is called the linear range. Within the linear range, plant development increases as the temperature increases and decreases as the temperature decreases.

With respect to basil, we start to see growth slowdown in the fall, winter and spring because the average daily temperature is getting lower in the greenhouse and the rate of new leaf appearance is decreasing. With the slower leaf unfolding rates, it takes longer for basil shoots to form enough leaves to become harvestable. While your greenhouse air temperature set points for heating and cooling may have not changed throughout the year, average daily temperatures may decrease for several reasons. First, with lower light intensities there is less radiant energy entering the greenhouse and increasing the air temperature. Additionally, plants will lose heat to the greenhouse superstructure and to clear night skies, which can result in plant temperatures below air temperatures.

Basil is sensitive to cold temperatures and has a Tbase of 47° F for leaf unfolding based on our research at Iowa State University. Alternatively, it grows very well at warm temperatures and our research shows leaf unfolding of sweet basil increaseses with air temperature up to 84 °F.

Therefore, one of the ways you can hasten growth and reduce the time to harvest is to increase your average daily temperature. Though you may be concerned about the cost of increasing air temperatures (and rightly so!), there are a few things to take into consideration. First, unlike ornamental plants we are not as worried about increased internode elongation from a positive DIF. Therefore, you can start by increasing your daytime air temperatures. Secondly, while raising your air temperature may increase heating costs, how much are missed crop turns from longer production cycles costing you?

Light

Temperature primarily influences the rate of development, while light primarily influences growth — an irreversible increase in weight or mass. Light drives photosynthesis, which produces carbohydrates that have a variety of fates, from becoming cell walls to stored starch. As the intensity of light increases, more carbohydrates are formed and weight increases. Alternatively, photosynthesis decreased under lower light. As such, reduced photosynthesis from low light levels are another contributing factor to the diminished growth of basil in the late fall, winter and early spring. Research at Iowa State University has shown that the optimal light intensity for production of fresh mass in sweet basil is 500 µmol·m^–2·s^–1 and light intensities are often much less than this from fall through spring. Additional research we have performed has shown that increasing the daily light integral (DLI) from 7 mol·m^–2·d^–1 to 15 mol·m^–2·d^–1 increases the fresh mass of sweet, lemon and holy basil by 144%, 207% and 208%, respectively.

To maximize transmission of light into the greenhouse, make sure your glazing material is clean and your superstructure over the plants is minimal. However, when ambient light levels are low, there is really only one way to appreciably increase your light intensity or DLI inside the greenhouse, and that is with the use of supplemental lighting. High-pressure sodium (HPS) lamps are the most widely used light source for increasing light intensity and DLI in greenhouses. Many types of light-emitting diodes (LEDs) have been introduced into the marketplace recently and, while this is a new technology that may be less familiar to growers, it shows promise as a supplemental light source. Whether HPS lamps or LEDs, diminished photosynthetic activity from low light levels is another contributing factor to the diminished growth of basil in the late fall, winter and early spring.

Research at Iowa State University has shown that the optimal light intensity for production of fresh mass in sweet basil is 500 µmol·m^–2·s^-1 and light intensities are often much less than this from fall through spring. Additional research we have performed has shown that increasing DLI from 7 mol·m^-2·d^-1 to 15 mol·m^-2·d^-1 increases the fresh mass of sweet, lemon and holy basil by 144, 207%, and 208%, respectively.

Whether HPS lamps or LEDs, a good starting supplemental light intensity is from 70 to 100 µmol·m^-2·s^-1. The number of lamps that you will need will depend entirely on the output of the fixtures, distribution of the light, and distance from the plants they are placed. Lighting companies can help provide support when trying to determine your needs and can assist you in putting together a lighting plan.

The author is an extension specialist and professor at Iowa State University. Reach him at ccurrey@iastate.edu

Photo © Liliya Trott | Adobe Stock

If you are wondering whether a shift to organic produce is right for your business in the new year, now’s a good time to evaluate 2020’s impact on markets and minds. While many consumers and industries are struggling with the effects of the pandemic, the organic produce industry realized significant growth. If there is one thing consumers are seeking right now it is peace of mind … or safety. We cannot deny there is a strong perception of safety and health associated with foods marketed as organic. If you are an organic produce grower, you have a unique opportunity to be an authentic solution to an excessively large public health problem.

Reports of record-breaking sales in organic produce were already hitting the newsstands by June of 2020. By the time Q3 reports were in, volume and sales were up by 15% and 16% respectively, according to the Organic Produce Network (OPN). It also bares mentioning that grocery stores buy more organic produce than restaurants. With consumers forced to stay home and most restaurant business on hold, it is easy math.

What is organic’s ceiling?

It has long been a topic of debate whether organic produce would or could capture a majority of market share with consumers. Yet, purchasing trends have been pointed — if in a slow and steady fashion — in that direction. At the end of 2019, organic produce already made up 15% of all produce sold, with sales up 5.6% according to the Organic Trade Association (OTA). Once all the numbers are crunched for 2020, larger increases will no doubt manifest. Wherever you fall on the issue of organics, it is hard to ignore the real market momentum.

One could argue that when or if the restaurant industry is able to rebound post pandemic, we may see some softening of organic produce sales. Even so, once consumers have been trained — or trained themselves —into a new way of buying and cooking produce, it is not likely that they will return completely to previous habits. I suspect post-pandemic, many consumers will stick with a reduced eating-out budget and more home cooking, including the organic produce that has provided safety and comfort during difficult times.

Ultimately the term ‘organic’ equates to ‘healthy’ for many consumers. This is an incredible advantage for the organic produce industry.

Beyond perceived safety of foods, it is nearly impossible to argue that being healthy and eating healthy will not continue to be a major consumer focus in 2021. COVID-19 has been a rude awakening for many Americans. With the immense stress on our minds and bodies, what and how we eat — and its impact on our stamina and ability to fight off illness — is front and center in our minds. It is something that’s forefront in my own mind as I am writing this column.

With organizations such as the World Health Organization, Harvard Medical School, The American Society of Nutrition and The New York Times (just to name a few) publishing pieces on how diet impacts nutrition and health in relation to Coronavirus, diet and the pandemic are now inextricably connected. Coupled with building resilience to viruses, many Americans are also going to be extremely focused on getting back to a “pre-COVID-19 weight.” Fresh produce and plant-based products are going to play a big part in the grand reset.

Photo © anilakkus| istock

Educate your customers

While organic produce sales are on the rise, so is organic food fraud — especially with imports. As a result, the USDA is proposing strengthening their regulations around organic certification. You can read more on their website here. While this may mean more hoops for you to jump through in a transition to organic production, transitioning a greenhouse operation to organic production is in some ways simpler than in-ground farming.

If you are considering going organic, or you have already made the commitment, consider also committing to better consumer education as a core part of your marketing. Education and consumer understanding of the benefits of organic produce needs improvement. I would love to see organic producers doing more behind the scenes videos for consumer consumption.

Not only is how you grow your produce fascinating to your end-users, but it also builds trust and confidence in your brand and organics in general. Because you will also need to combat public perception of organic produce fraud and food safety, transparency will be even more important. If you grow and sell locally, or in a small region, this is a big benefit you can leverage in your consumer marketing.

Ultimately the term “organic” equates to “healthy” for many consumers. This is an incredible strategic advantage for the organic produce industry as we move forward into 2021. If you have been considering a shift to organic production, 2020 may just be the tipping point you needed to nudge you forward.