2018 State of Lighting Report - 2018 State of Lighting Report: Research

The latest stats and figures from the 2018 State of Lighting Report show that LED use is on the rise.

July 9, 2018

The basics

What crops does your location grow under cover (greenhouse, hoop house/high tunnel, growth chamber, etc.)?

In what state/province is your location? If your company has multiple locations, please select the state/province for the location in which you work.

How many square feet (square meters) does your location devote to growing crops under cover?

How much revenue (in U.S. dollars) did your location generate from its under cover crops in 2017?

As we did in 2016, we surveyed both our Greenhouse Management and Produce Grower readers to gain insights into who is incorporating lighting into their operations, the reasoning behind their decision, and what effect it has had. Seventy-nine percent of respondents grow ornamental plants and 41% grow produce; some may be growing both. We also heard from a limited number of cannabis growers. This year, the mean revenue was $309,000, up from $229,000 in 2016, and we heard from 7% more growers with 100,000 sq. ft of growing space or more.

Lighting the path

Does your location use supplemental lighting in its production of crops under cover?

Are you or would you be personally involved in purchasing or using supplemental lighting for your location?

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.

For what reasons does your location use supplemental lighting?

Propagation was an option we added this year based on the number of people who included it as a fill-in answer in 2016, and nearly half of growers said they’re utilizing lighting for that purpose. However, day length extension (up 7% to 71%) and supplemental lighting during low-light periods (up 4% to 65%) remained the most popular answers. Using lighting in this way can enable growers to extend their seasons even when natural lighting conditions are less than ideal for the crops they’re producing.

What are the top three sources from which you typically receive information on supplemental lighting for under cover production? Select up to three.

Growers are still relying primarily on trade publications, both print and digital, for reliable information about lighting. This year, trade shows proved more popular with respondents than word-of-mouth as a method for expanding their knowledge. We also noted a 6% decrease in reliance on industry researchers and an increase of 8% on lighting manufacturers websites, as compared to 2016. Webinars was a new option this year, and 9% of growers like to get their information that way. Overall, there seems to be an increase in online information acquisition.

Kyle Banas, Nursery Manager/Head Grower

Pizzo Native Plant Nursery Leland, Ill.

We have used HPS and LED but only for photoperiod extension and supplemental light. We have seen the best results when using them to extend day lengths which helps with germination of some wetland and prairie species, namely carex species.  

Duke Stockslager, owner

Stockslager’s Greenhouse & Garden Center New Lebanon, Ohio

One of the biggest successes is the [LED] lighting that we’ve put into [our propagation houses]. We saw such a tremendous change from the HPS lamps and the metal halide to these. We knew that [HPS and metal halide] were just taking the energy and running the meter, so we knew we could do better. We did not anticipate the time savings that we would get on cuttings [with LEDs]. We used to be happy with 15 to 18 days on rooting a geranium cutting, and we’re down to [10 days].


How often is daily light integral (DLI) included in your location's under cover production protocols?

Based on this year’s results, more growers are measuring light in general, as well as daily light integral (DLI), in their operations. This year, 8% fewer growers said they don’t measure light levels, and more growers are using micromoles (up 4%) and lumens (up 11%), both at 21%. Ten percent more growers selected “Often” for DLI measurement while 10% fewer said they never measure DLI.

Professor and Greenhouse Management columnist Christopher J. Currey spoke with us recently about the importance of light measurement. “You need both instantaneous measurements, micromoles per meter squared per second (µmol·m-2·s-1), as well as cumulative measurements, DLI,” he says. Each measurement has its own benefits and can serve growers in different ways. For example, instantaneous light readings are useful for daily lighting decisions. “If you have a retractable shade cloth, light intensity is going to help tell you when to draw that cloth over the plants on a sunny day, or when to leave the plants uncovered if it’s a rainy day,” Currey says. Or growers can set an environmental control to automatically turn off lights when the ambient light reaches the desired light intensity, and turn them back on when levels dip below a set point.

Knowing the DLI levels in the greenhouse is also vital for longer-term decisions, Currey says. “DLI is good for knowing in general how much photosynthetic light you’re getting,” he says. “It’s also good for making seasonal lighting decisions: when [to] paint whitewash on our greenhouse, when we should turn our lights off and keep them off, when we should apply permanent shade cloths, when we should start to turn our lights back on again, etc.”

For more on the topic, you can read Currey’s April 2018 Production Pointers column, “Photosynthetic light: instantaneous vs. cumulative measurements,” at

How are under cover light levels measured at your location?

Lloyd Traven, Owner

Peace Tree Farm Kintnersville, Pa.

We’re not measuring light levels other than outdoors; we are not physically measuring inside the greenhouse. We have an Argus environmental control system that triggers all the light systems on and off, based on the light level and the rate of change of the light level [outdoors].

Jessica Marlowe, Propagation tech

Hoffman Nursery Rougemont, N.C.

We have a light meter and use the data from it to improve our production. We took sample readings in our older structures and then started monitoring light levels in the first section of our new greenhouse when it was finished. Some crops were growing slowly in the new section. Measuring the light allowed us to compare older and newer houses and figure out that light was the difference. We moved crops with lower light requirements (Carex) to that section to take advantage of the conditions. We also wanted to know if the new greenhouses could serve as overflow space for seedling propagation. Monitoring the light levels let us know where the best spots would be.

Types of lighting used

What types of supplemental lighting does your location use to grow each of these crops under cover? Select all that apply. Note: The respondents to this question answered previously that they grow these crops.

HPS, LED and fluorescent lights were the top three light sources for all of the ornamental crops above, with somewhat similar statistics as we saw in 2016. However, there were significant increases of between 16 to 18% in LED use in ornamental categories, with more than half of growers using LEDs for Stage I, II and III tissue culture, up from 40% in 2016. In that same category, fluorescent use fell by 35%, and incandescent by 12%. Incandescent light use was down at least somewhat across all categories.
LEDs were also more prevalent this year in edible crop production. In high-wire crops, LED use nearly doubled, increasing from 15% to 28% this year; HPS also saw the same increase in this category. LED use in lettuce rose 20%, while it increased 10% and 16% in microgreens and strawberries, respectively. Fluorescent lighting was down overall as well.

Overall, what percentage of your location's crops grown under cover with supplemental lighting is lit by each of the following types of lighting?

If we take the average of all growers’ responses for crops and types of lighting used, we can see that the average grower would light about a third of their crops with HPS lights, and a little less than a third with LED and fluorescent lights, respectively, and less than 10% with a combination of metal halide and/or incandescent. To give these numbers more context, we can compare them to the 2016 results, when we would’ve seen the average grower using 35.1% HPS, only 15.8% LEDs, 34.1% fluorescent (7.3% more than in 2018), 7.7% metal halide and 7.3% incandescent. It will be interesting to see how these percentages change as growers phase out incandescent and metal halide lights, and possibly make the switch from HPS to LEDs.
In the following charts, we break down the light usage by type.

Overall, what percentage of your location’s crops grown under cover with supplemental lighting is lit by each of the following types of lighting?

Fluorescent and metal halide use in floriculture and edible production is about the same as it was in 2016. In HPS usage, 7% fewer growers are using these lights for 100% of their operation; however, there was an increase of 11% in the 50-99% range. This may be because of growers who are slowly transitioning parts of their greenhouse to other types of lighting, such as LEDs. Neither metal halide nor incandescent lights are widely used, with 80% of growers saying they don’t use them, respectively.

The biggest change we see in the LED category is an 11% increase in those growing 50-99% of their crops using LED lights; we also see a 5% increase in those using LEDs for 1-49% of their crops. Those who say they’re not using LEDs at all dropped 19%, to 42% total.

Lloyd Traven, Owner

Peace Tree Farm Kintnersville, Pa.

[LED] technology has exploded, and amazingly, we jumped on that bandwagon. The main purpose for the lights was growing basil and for propagating. … We feel that [LED lighting] will revolutionize the way we grow here. It certainly is revolutionizing the way we propagate. I think that it’s not suitable for all growers. … But if you are a propagator, I can’t imagine how you do it without.

We are definitely cutting time off of our propagation cycle. We are greatly increasing the quality of what we put out. Our propagation business is almost triple this year [compared to] what it was. And we’re getting really good germination and really good uniformity.

Our basil [plants are] just so uniform [too]. It’s amazing, and that’s what we need. We supply Wegmans twice a week and they want the same plant every time. I am that rare wholesale greenhouse that has cash flow 52 weeks a year.

Jacob Stockslager, Grower

Stockslager’s Greenhouse & Garden Center, New Lebanon, Ohio

When we were under the metal halide and HPS [in our propagation house], the heat coming off of them would stress our cuttings. ... With the LEDs, they’re getting the light concentration they need, but the stress of the heat isn’t there. … That is another great benefit from these lights. 

Christopher J. Currey

Iowa State University

Increased popularity [of LEDs] could be attributed to potentially both the photosynthetic LED fixtures as well as the flowering lamp LEDs that are replacing incandescents and pie plates.

This year, half of all respondents chose the new option “financially invested in current non-LED lighting system.” It edged out those who are satisfied with their crop production using other lighting sources, which dropped 14%. One other significant change was in LED knowledge. Nine percent fewer growers said they lacked reliable information about LEDs, a good sign that the industry is becoming better informed about LED lighting as more trialing and research is being conducted and shared.

Looking forward

Is your location considering installing, expanding and/or replacing its supplemental lighting within the next 3 years?

Compared to 2016, significantly more growers are looking to install new systems or change their current lighting systems in the next year to three years — about 13%. The number who said no, they were not considering it, dropped 16% from nearly two-thirds of grower respondents to just under half. When it comes to which type of lighting they would prefer to purchase, LEDs are once again the most popular response, up 4% from 2016 to 86%; all other lighting systems saw decreased numbers compared to 2016.

What type(s) of supplemental lighting is your location most likely to purchase for the expansion/replacement? Select all that apply.

Duke Stockslager, owner

Stockslager’s Greenhouse & Garden Center, New Lebanon, Ohio

As the cost comes down on these LED full-spectrum fixtures, [we] would love to see them in the entire range. What that does for us growing in February, March, mid-April, [is controlling] that crop, and [having] a much finer crop ready for sale [in May]. We’re seeing the benefits of that and the day will come when I’m certain we will have [LED] lighting throughout the range. 

Jessica Marlowe, Propagation tech

Hoffman Nursery, Rougemont, N.C.

We just recently started trialing lighting in our seedling crop propagation area. The lights are LED fixtures from two different manufacturers. The manufacturers are working with us to set up a series of evaluations, but we are just getting started. We began with seedling propagation because it’s a smaller, more controlled environment, and we can see results more quickly with the short turnover. We thought the seedlings might dry out under the fixtures, but so far that’s not the case. Initially, we’re focusing on the effects of day length. We hope for better germination rates, increased vigor, and reduced elongation. First impressions are that the seedlings under lights are darker green and stockier. However, it’s still early in the process, so it’s too soon to come to any conclusions. We hope to move on to trial other aspects of the lighting, like wavelength and timing of application.

How important are each of the following factors when selecting an LED lighting fixture?

What growers are looking for in their LED lighting fixtures has remained somewhat consistent over the past two years. However, we did note some important shifts. Ten percent more growers ranked passive cooling mechanism as 5, or very important, which elevated the average ranking from 3.0 to 3.3. Light intensity and dimmable light intensity both ranked higher with more growers, as did both company and product reputation.


The data from the 2018 State of Lighting Report research supports what we’ve been informally seeing and hearing throughout the industry — growers are increasingly interested in learning about lighting their horticultural crops, whether they grow flowers or food. There is a continuing shift from incandescent, fluorescent and metal halide fixtures to high-efficiency HPS and LED lights as more research supports the benefits of the latter two. We’re looking forward to seeing how these trends evolve over the coming years.