Culinary herbs are a popular crop for recirculating hydroponic production in greenhouses and other controlled environments. Unlike the vining, fruiting and high-wire crops, culinary herbs are produced for their flavorful foliage. This aspect, combined with their short crop time, put them right next to lettuce and other leafy greens. However, the specific light requirements of culinary herbs are not well understood. Recent research we have conducted at Iowa State University has aimed at better understanding how common culinary herbs respond to the daily light integral (DLI) during finishing in the greenhouse.

We took eight of the most common herbs grown in hydroponic systems, including basil (Ocimum basilicum), sage (Salvia officinalis), mint (Mentha spp.), dill (Anethum graveolens), parsley (Petroselinum crispum), cilantro (Coriandrum sativum), oregano (Origanum vulgare) and thyme (Thymus vulgaris). These represent many of the commonly grown species in commercial controlled environments. Seedlings were grown in nutrient-film technique (NFT) systems. The nutrient solution pH (6.0) and electrical conductivity (1.5 mS·cm^–1) were maintained the same across all systems and were adjusted daily.

The NFT systems were covered with shade cloth that reduced light by 33% or 69%, or no shade was used. High-pressure sodium light operated from in the morning and the evening, and shade cloth was only drawn to prevent leaf scorch as needed. This experiment was repeated numerous times from the fall through into the next summer, resulting in a range of DLI values from 2 to 20 mol·m^–2·d^–1 for all eight species. Three (basil, cilantro, dill, oregano, sage and thyme) or four (mint and parsley) weeks after transplanting into systems plants were harvested, at which time fresh were recorded.

We saw a similar response in fresh mass to DLI that we found with height. The fresh mass of parsley, mint and sage increased as DLI increased up to ~15 to 16 mol·m^–2·d^–1, after which weight started to decrease. Alternatively, fresh weight increased linearly with DLI up to 20 mol·m^–2·d^–1 for basil, cilantro, dill, thyme and oregano, with no decrease at high DLI values.

Classifying crops by light requirements can help simplify production. Using fresh weight as the most important factor and grouping crops by as having low (5 to 10 mol·m^–2·d^–1), medium (10 to 20 mol·m^–2·d^–1), high (20 to 30 mol·m^–2·d^–1) and very high light (>30 mol·m^–2·d^–1) DLI requirements, we found parsley, mint and sage are medium-light crops. Alternatively, basil, cilantro, dill, thyme and oregano have high or very high DLI requirements, as the optimal DLI was not identified with the range of DLI values in our study.

Given the response to light, it is clear that supplemental lighting can boost the productivity of culinary herbs under light-limiting conditions. However, while all species increase growth with increasing light, the weight produced in response to increasing light varies with species. For example, given the same amount of supplemental light, dill may produce 25 times the amount of additional growth that oregano would. This variation affects the economics of supplemental light management. Assuming the same costs for providing the same amount of supplemental light, your return improves on lighting those crops with greater productivity.

If supplemental light is not available, there are ways to improve yield under light-limited conditions. For example, you can increase the planting density by using closer spacing in the finishing area or increase the number of seeds sown for each transplant. While the individual plant weight is still low under diminished light, the yield per square foot increases with the greater planting density.

If you are trying to increase productivity of your hydroponic herbs, evaluate the light in your facility. Supplemental light is going to be useful for most crops in many locations and should be evaluated as another yield-boosting production strategy.

Currey (ccurrey@iastate.edu) is an assistant professor in the Department of Horticulture at Iowa State University. Litvin (alitvin@iastate.edu) is a graduate student at Iowa State.

Photo courtesy of United Fresh Produce Association

United Fresh announces 2020 Expo at San Diego Convention Center

After the success of the 2019 convention, United Fresh will launch a four-year rotation with San Diego as its first stop.

At the conclusion of the United Fresh 2019 Convention, it was announced that the United Fresh 2020 Convention & Expo will take place June 16-18 in San Diego, California, marking the first stop in a new four-year city cycle for the trade show.

“Chicago has been good to us,” said United Fresh President & CEO Tom Stenzel. “But the time has come for us to broaden opportunities across the industry by taking the show on the road.”

>> Read the full story here.

Photo courtesy of Rutgers University

Four new Rutgers sweet basil varieties now available to home gardeners

Rutgers plant scientists spent a decade evaluating and breeding downy mildew resistant basil.

Four new sweet basil varieties resistant to downy mildew disease, which destroys leaves, are now being sold to home gardeners and commercial farmers across the U.S. thanks to years of breeding and selection at Rutgers University.

Two of the four varieties also show high resistance to Fusarium wilt, another soil-borne disease. The four new downy mildew-resistant sweet basils are Rutgers Devotion DMR, Rutgers Obsession DMR, Rutgers Passion DMR and Rutgers Thunderstruck DMR.

>> Read the full story here.

Photo © opra | Adobe Stock

Village Farms plans to begin hemp production in Texas

The Canadian-based vegetable grower is converting a 1.3-million-square-foot greenhouse for cultivation of high-cannabidiol (CBD) hemp and CBD extraction.

Texas Governor Greg Abbott has signed into law Texas House Bill 1325 (the “Texas Hemp Legislation”), which effectively legalizes the cultivation of hemp and processing of hemp and hemp-derived products, including cannabidiol (CBD) in the state.

As a result of this legislative change, Village Farms has begun conversion of half of its 1.3-million-square foot, ultra-high-tech Permian Basin greenhouse for both cultivation of high-cannabidiol (CBD) hemp and CBD extraction.

>> Read the full story here.

Photo courtesy of John W. Bartok, Jr.

As we transition into winter, energy use begins to increase and greenhouses are subject to severe weather. Reviewing the following tips while you perform an inspection of your facilities and equipment will point out where maintenance and improvements need to be made.

Infiltration

Air gaps are a major source of heat loss in many greenhouses. A 48-inch fan shutter with 1-inch gaps between blades can allow as much as 25,000 Btu per hour (Btu/hr) to escape. Inspect these areas as you walk your greenhouse’s perimeter:

1. Glazing: Secure glazing to prevent plastic failure, repair or replace torn plastic, and adjust inflation pressure to ¼-inch static pressure. Clean and lubricate inflation blowers. Remove any shading, as light is critical during winter.

2. Foundation: Seal cracks in the foundation and baseboards with foam caulk or insulation board. Weatherstrip around personnel and vehicle doors with rubber or foam.

3. Gutters: Remove leaves, twigs and trash in rain gutters and downspouts. Drainage swales should be clear so water can drain away from the foundation. Space between houses should be obstruction-free for snow storage or snow removal purposes.

Structural integrity

Snow and wind can place significant loads on the greenhouse. Inspect inside the greenhouse for:

4. Loose truss and frame connectors: Tighten bolts, cross connectors and fasteners.

5. Diagonal frame bracing: Check to see that cables are tight and rigid braces are secure.

6. Hoop houses: Have 2-by-4 posts available to be placed under the ridge if heavy snow is predicted.

7. Energy screens: Adjust cables and check for tight end- and side-screen closure to prevent chimney effect heat loss.

Yearly furnace and boiler service

Servicing your boiler is key to efficient and trouble-free operation, and maintenance can be paid for with a 2% increase in efficiency.

8. Clean radiators, pipes, ducts and heat exchangers for increased heat output.

9. Calibrate your thermostat/controller accuracy against a digital thermometer.

10. Chimney and flue pipes should extend 2 feet above the roof ridge for better draft.

11. Enclose outdoor fuel tanks for a warmer fuel temperature and greater vaporization of propane in the tank or fuel oil in the firebox.

Fans and vents

12. To save energy and reduce cold air drafts on plants, close fans and vents not needed for winter cooling.

13. Drain and close the evaporative cooling system.

14. Check fan belts for wear, tightness and alignment.

15. Horizontal Air Flow (HAF) fans should be cleaned and serviced to increase air flow by up to 25%.

Water systems

16. Water systems need periodic service. Drain hot and cold water tanks to remove sediment and reset water pressure. Clean filters and screens.

17. Check hot water tank temperature. For most uses, 120° F is adequate. Insulate pipes with ½-inch foam insulation, at minimum, to retain heat and reduce condensation.

18. Eliminate water leaks. 60 drops/minute wastes 113 gallons/month.

Backup power

Backup power is a must for winter operation. Prepare by:

19. Operating the standby generator monthly. Keep extra fuel on hand.

20. Check and operate alarm system weekly.

The author is an agricultural engineer and an emeritus extension professor at the University of Connecticut. He is an author, consultant and certified technical service provider doing greenhouse energy audits for USDA grant programs in New England.

For years, the biggest trend in food has been to buy fresh, buy local and buy seasonal. It’s not only health-conscious and eco-friendly consumers, it’s foodies as well. The nutritional value is great, but the taste is what drives many to jump on the farm to table bandwagon.

For those same reasons — taste and nutrition — mushrooms are gaining popularity in the American diet. Mushrooms are rich in vitamin B, potassium, niacin and other nutrients, but they also provide a meatiness without the cholesterol, fat and sodium that usually accompany that rich flavor. And the average consumer is taking notice.

Mushrooms are popping up in all kinds of places you wouldn’t expect. From mushroom coffees and teas to dietary supplements, they’re gaining popularity for their medicinal and nutritional value. (Something other cultures have known for years.)

As more and more Americans move to a plant-based diet, mushrooms are really seeing their moment in the sun. And this is going way beyond the portabella burger you used to find as the vegetarian option on the menu. What was once just a fungus you’d see in a salad or as a pizza topping is now a culinary delicacy worthy of a high price tag. Besides truffles, varieties like porcinis morels and chanterelles can bring in some serious cash. (Morels can be as much as $90 a pound when they’re in season.)

In fact, some mushroom growers are even marketing their products as a meat alternative or a meat additive like Monterey Mushrooms’ Let’s Blend line, designed to mix right in with ground meat. The idea is to lower meat consumption and increase plant-based ingredients even if that doesn’t mean eliminating meat altogether for a vegetarian diet.

But it’s all about availability. Without access to these new, trendy foods, chefs would have no way to innovate their menus with ingredients like shiitake or oyster mushrooms. Luckily, mushrooms are easy to grow if you know what they need. You can find out how growers from different controlled environment agriculture operations are hopping on trend and turning a profit.