The basics

Sole-source lighting with LEDs in strawberry production
Photo: Christopher J. Currey

In order to get a good read on who’s using lighting for this study, we polled both our Greenhouse Management and Produce Grower readers. 74% of respondents are growing an ornamental crop, whether they’re propagating it, selling it as a young plant, or growing it to finished size. 40% of respondents are growing produce, with high-wire crops topping the list. A small portion of those who answered, 2%, are growing cannabis.

Nearly three out of every four growers would like to see new technology being used successfully in some form before incorporating it into their own business. However, 30% of those surveyed would be more swayed by seeing the technology used successfully by their peers than by other proof that it works, showing the influence of industry members and the importance of networking. Interestingly, those growers at operations generating $250,000 or more in revenue are more likely to be in this group that is influenced by their peers’ success; 40% of them answered this way versus 26% of those in the below $250,000 revenue group.

On the two extremes, we see that there are some more extreme risk takers within the group who are looking to beat their competition to the market (7%) as well as those who choose not to take a risk and to invest in new technology (6%).

The mean revenue among growers who answered this survey was $229,000. Those growers who also stated that they are using lighting in their operations reported slightly higher numbers, with those operations coming in at an average $327,000.

Shining some light on the situation

Overall, we see that slightly more than one out of every three growers are using lighting to produce crops under cover; the remaining approximately two-thirds of the grower respondents isn’t currently using lighting. However, upon closer examination, these numbers seem to be largely related to their respective revenues. When we look at growing operations with reported revenues of $250,000 or more, 56% of those operations are utilizing lighting in some fashion, while only 31% of those reporting lower numbers are doing so. It’s therefore more likely that the bigger the operation, the more likely it is to be implementing lighting into their production.

Elmira's Own Tomatoes grown under LEDs at Floralane Produce in Ontario
Photo courtesy of Philips Lighting

From this point forward in our research results, the answers provided will be from the 66% of respondents who are based in the U.S. or Canada at an operation that grows at least a portion of its under cover crops using lighting and who are (or would be) personally involved in purchasing/using it for their location.

Most growers are using electrical lighting as a means of providing plants with more light than would naturally be available at the time they’re being grown, whether that’s to extend the numbers of hours of light or supplement the existing light.

Growers are getting their information about horticultural lighting from several different sources, with trade publications clearly topping the list; three out of four growers consult them for their lighting needs. However, if we look at the second, third and fourth sources, the results are similar, with about a third of respondents choosing trade shows, industry researchers and lighting manufacturer websites. As we saw earlier when discussing technology adoption, we see that many growers are talking to peers about their production and, in this case, sharing information specifically about lighting.


Ensuring that the daily light integral (DLI) in your greenhouse is important to guarantee that the type of plant you’re growing has adequate light. Greenhouse Management columnist John W. Bartok explained DLI and highlighted its importance in a recent article (read the whole article at “The daily light integral was developed by scientists to provide a measure of cumulative photosynthetically active radiation (PAR) received by plants over the course of the day,” Bartok states. “It integrates light intensity in micromoles per square meter per second (µmol/sq m-sec) and totals this over a 24-hour period. The total daily integral is expressed as moles per square meter per day (mols/sq m–day). The concept is similar to totaling daily rainfall measured in inches per day.”

DLI needs depend on the crop. Low-light plants need 3 to 6 mol/sq m-day, medium-light plants (most annuals) need twice that amount, and high-light plants like perennials and vegetables require at least 12 mol/sq m-day. If your measurements show that your light levels are significantly different, you may want to consider supplemental lighting, Bartok says. If your operation isn’t currently measuring DLI, there are several low-cost measurement tools available.

Types of artificial lighting used

Within the ornamental crops, fluorescent and high pressure sodium (HPS) are leading the pack for the majority. The main notable difference is between the Stage I, II and III tissue culture producers and all other ornamental crops, from other stages of propagation to finished plants. In the former, tissue culture producers are using LEDs at a higher rate — 40% — than LEDs are being used in any other ornamental crops. In fact, all types of lighting are being used at a higher rate than other crops, due to the nature of tissue culture production.

In contrast to the lighting breakdown we see in ornamental production, fluorescent topped the list in every edible crop, with at least a third using that lighting source. Lettuce and microgreens were the most likely to be using LED lighting, with 26% and 35% of growers, respectively, incorporating it into their operations. In cucumber, tomato, pepper, eggplant and strawberry production, growers were just as likely to use LEDs as HPS. Strawberry growers were just as likely to use metal halide and incandescent as LED or HPS sources.

There is considerable research being conducted on the effects of light spectrum on taste, nutrition, color and other qualities of edible crops. One of the reasons that we see LEDs being used slightly more with edible crops may be due to the possibilities of customizing the light spectrum to create the perfect “recipe” for lighting success. See S19 to read more about some of the new research in this area that was presented at the 2016 International Symposium on Light in Horticulture.

Cannabis growers seem to be using a variety of lighting sources, and possibly multiple types at each operation. All growers who responded that they grow cannabis chose at least one lighting source being used in their operation, with HPS topping the list, followed by a tie between fluorescent and LED lighting.

If we look at the overall picture, incandescent and metal halide are the least popular types of artificial lighting, with 78% and 79% of growers reporting that they don’t use it at all in their operations. Fluorescent lighting is the most popular lighting source, with 54% of growers using it, followed by HPS, which is used by 51% of growers.

Because a good portion of the lighting research being done in the horticulture industry is with LED lighting and seems to be an increasingly popular choice, we asked growers why they wouldn’t use this particular light source. As mentioned in the introduction, this type of lighting has been increasing in efficiency and application since the 1980s, and especially in the past five to 10 years.

When it came down to it, nearly half of respondents said that what they’re using now is working for them, and they didn’t see a need to change. Slightly more than a third didn’t see the return on investment for LED installations, in spite of the energy savings incurred. For the fifth of respondents who need more information on LEDs, we’ve got you covered and will be continuing to publish practical information to help you make the best decisions going forward. If you’re currently using HPS lighting and thinking about making the switch to LEDs, read “Do the math, see the light” in our January 2016 issue to determine if it’s economically feasible for your operation, accessible at

A research facility at Colorado State University with LED toplighting modules
Photo courtesy of Philips Lighting

Looking forward

One out of three growers say their operation plans to install, expand or replace its lighting in the next three years, a good sign that there will be continued growth in this area. Growers looking into this equipment are overwhelmingly planning to purchase LED lighting — 82% — over HPS lighting (21%). Respondents could select more than one type of lighting, so it’s possible that we’ll see a combination of new LED installations in some areas of the greenhouse, as well as added HPS or fluorescent lighting being installed elsewhere.

Because of the high interest in purchasing LED lighting, we also looked into the most important factors in selecting a particular unit for the greenhouse. Light spectrum (72% ranked it as 5, “very important”) and energy efficiency (69% ranked it as 5) topped the list, which makes sense because the draw of LEDs for many growers is the ability to use specific light spectrum “recipes” and save on energy costs. LEDs also have a longer lifetime than many other light sources, which makes them an attractive option. However, the relatively high cost of buying these units compared to others can be a deterrent for potential users, hence the 4.5 rating in the scale above.


Although it can be a significant monetary investment, lighting can be a viable and profitable addition to ornamental and produce operations. Benefits can include improved efficiencies, reduced labor needs, plant loss prevention and an extended growing season for some growers. With the continued development and research into technologies like LEDs, growers have more options than ever to tweak their lighting to best suit their needs, enabling them to create the ideal solution for their greenhouse.

July 2016
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