Maximum Yield USA August/September 2019 | Page 46

“The problem with LEDs right now is the fixture costs. I think they are three to five times more expensive per fixture than HID lights like MH and HPS, but they are getting cheaper.” “Completely indoor, like vertical farms, are almost all LEDs... or at least they are going to be,” Mitchell says. “This is because with LEDs you don’t have to worry about the fixtures blocking solar. The problem with LEDs right now is the fixture costs. I think they are three to five times more expensive per fixture than HID lights like MH and HPS, but they are getting cheaper.” Go Green Mitchell stressed these aren’t fruiting vegetables being grown commercially with LEDs, these are quick-turning, leafy green crops like lettuce, kale, and arugula. Quicker yet are baby greens and the even-faster-maturing microgreens, as they require practically no light. “For the most part, tomato, cucumber, and eggplant are high-wire plants and tend to require a lot of light,” Mitchell added. When I asked what mistakes indoor growers seem to make most often, Mitchell was hesitant to think of them as mistakes, but more a lack of knowledge. Not having the right light prescription for your plants combined with high humidity can create some leaf burn and other issues. This is bad news for the commercial grower because this renders the greens unmarketable. 46 Maximum Yield “You can get lighting prescriptions from the different compa- nies, but you know, it takes more than light to grow plants. It takes carbon dioxide. It takes nutrients, water; it takes the correct temperature; it takes humidity and so all those things factor together,” says Mitchell. “It’s still a fairly young indus- try so there are risks involved in any new crop you might try to grow without having the experience. So, a lot of these compa- nies are doing what are called light recipes, but I’d say it’s really growth recipes you need to work out that include that litany of environmental factors that interact with light.” Mitchell stated that because the photoperiod of tomatoes is so long, they are one plant that doesn’t do well indoors. For the home grower, if you wanted to grow some grape or cherry tomatoes or a few dwarf species with LEDs you may get some tomatoes. There are light banks available (even LEDs) that may work on those types but not so much the standard toma- toes we see in the garden. They just don’t do well under solely artificial light conditions. “So right now, the cards are not there for growing indoor tomatoes productively and certainly not commercially. For the home grower, as I said, you could probably grow some cherry tomatoes on a very small scale in your basement, that might work,” says Mitchell. “If you ask someone else, say someone at an Extension office, they may see growing tomatoes indoors differently.” As a researcher, Mitchell says his views are purely objective. “I just know the state-of-the-art for LEDs right now and it’s just not there for growing tomatoes. Sole-source lighting works well for greens and that’s why they grow them. For the homeowner, if you have a greenhouse and supplement the natural light with LEDs you can get a decent yield.”