“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.”