Growers shopping for LED lighting face a dilemma: opt for purple hues to cultivate their crops or select from the latest full-spectrum solutions boasting the benefits of sunlight. The debate is ongoing and, while each controlled environment facility has its own lighting needs, the facts can help you make the best decision for your greenhouse or indoor farm.
Here are five things to know about full-spectrum lighting, as well as additional information about increasing yields and boosting revenues with an LED strategy. Is white light optimal for your operation? As many growers are learning, you should be cautious when stacking the claims and choose carefully.
- 1. It Depends on Whom You Ask
There is no strict definition of “full spectrum”—the term is not specific to any industry, standard or code. Rather, it is a marketing label to describe light sources that emulate natural daylight (“white” light). As such, full spectrum can mean different things to different manufacturers, making a true apples-to-apples comparison of competing products tricky.
- 2. Coatings Can Hide the Truth
LEDs produce white light in two ways: by mixing red, green and blue diodes; or, more commonly, by applying phosphor coatings to single diodes, such as a yellow phosphor applied to a blue diode to produce white light. However, coatings can degrade over time, causing color shifts, and thicker coatings may limit light output efficiency. There is no such thing as a white LED—only LEDs that produce light that appears white to our eyes.
- 3. Wide Coverage Is Not Full Coverage
The complete solar spectrum includes ultraviolet (UV) and infrared (IR) wavelengths that many full-spectrum products do not produce. Such lights effectively span the visible spectrum—merging violet, indigo, blue, green, yellow, orange and red together—but are less concerned with UV and IR exposure that can benefit certain crops. In other words, full spectrum is not a true substitute for outdoor growing conditions most of the time.
- 4. Purple Is Proven
Science supports the fact that the colors most absorbed by plants to promote photosynthesis are red and blue (that is, chlorophyll absorbs light most strongly in the red and blue portions of the spectrum). Similarly, ongoing research by Current and its partners continues to prove red and blue grow lights are the most efficient, deliver the highest output (umol/s) and produce consistently excellent results. For example, in greenhouses where sunlight already provides the yellow and green wavelengths plants need, a supplemental purple grow lighting strategy can boost production year-round.
- 5. Looks Aren’t Everything
Some growers avoid purple light because employees might not like it. This is easy to work around with strategically placed work lights that produce bright white light. While these lights tend to be less efficient than full-spectrum fixtures, they only need to run when workers are present, making the impact to OPEX minimal. Grow room glasses are another option for enhancing employee comfort without overspending.
This is not to suggest full-spectrum lighting is ineffective—many growers use white light successfully, especially in indoor farms. Rather, it is a reminder that plants derive energy for photosynthesis across the entire light spectrum, with certain red and blue wavelengths being most beneficial. Taking advantage of how plants react to specific wavelengths at various stages of growth is the aim of LED lighting manufacturers like Current.
Grow lights don’t have to be purple, but white light is not always the answer. The best strategy is to align yourself with an expert who can see the bigger picture, including your goals for individual crops. When purchasing LEDs, ask questions, and don’t settle for the partial truth about full spectrum.
Want to know more? Download Current’s ebook, “LED Grow Lighting 101: A Guide to Greater Yields, More Harvests and Higher Profits.”