LED grow lights have come a long way since they were introduced in the 1990's. From left: a multi-wavelength bulb; a white light panel; a set of T8 tubes, a flexible multi-color cable. The colors are not decorative; each corresponds to wavelengths which boost plant production at various stages.
LED grow lights are a recent addition to the high intensity lighting world, both for general use and for hydroponics in particular. While they offer a variety of advantages, they also have some potentially serious drawbacks, at least for now. Let's take a look.
A few years ago I worked for a farm which had LED grow lights in one of their seedling houses. Their setup was interesting, because they had the standard grow benches for the bulk of their seedlig trays. Underneath the benches, in space normally wasted because it's too dark for growing, this farm had installed LED grow lights to provide for more growing area. And that is where these new lights shine the very brightest, no pun intended. They are so small, lightweight and intense, they can provide a whole lot of light in very small places, where other light fixtures wouldn't fit and/or would quickly overheat. LED lights allow growers to make the absolute best use of every last nook and cranny available in their greenhouse or grow-house. Instead of measuring grow space in terms of single bench rows, growers can measure grow space in terms of volume - multiple shelves of seedlings in a single greenhouse, all receiving the light they need for good germination. It would be like having multiple grow houses, but without the extra heating requirement.
The advantages don't stop there. These
lights are super-small in profile, and do not have heat buildup issues like
some other forms of HID lighting. They can be configured in a amazing
variety of shapes, all the way from a single strip of lights for a very narrow
area, to a panel of lights like in the photo above. I've even seen some
products where LED light strips are located between fluorescent tubes within
the tube fixture, so that the single fixture light output is vastly higher than
with fluorescent tubes alone. For putting the max amount of light in the
smallest possible area, without heat buildup, nothing compares with these
little gems. Another advantage is that they last, and last, and last
awhile longer. Fluorescent tubes, HPS and metal halide bulbs all
eventually burn out; LED lights supposedly last 10x longer than any of them.
As if that wasn't enough, LED lights can be configured to emit exactly
the portion of the spectrum wanted or needed, ranging from the particular
wavelengths needed for fruiting, to full spectrum for any stage of growth.
If there was one light that "does it all", this little light is
The main disadvantage of LEDs so far is their cost. They are still so new and so few people are using them, that production costs are still relatively high. I have spoken with a few growers who are using them as their primary supplemental light source, and they are very happy with their fixtures. Some are so happy that they strongly encourage others to pursue this form of lighting, rather than going with older forms of lighting such as metal halide, HPS and compact fluorescents. While I can appreciate the efficiency of these units, the cost is still a big issue for a lot of growers, including us. At present, until that cost comes down, the only time I'd use them is as described above, to make the most of growing space where small, lightweight fixtures are the only ones that would work. Even then I'd have to make sure the cost of the fixtures would be offset by the income from the increased growing space and/or the extended lifespan compared with other bulbs (which may already be the case).
LEDs have captured the attention of many university agricultural researchers, for both conventional and hydroponic systems. Those researchers, in turn, have put LED lights through a variety of testing scenarios, and written about their findings. Additionally, some commercial sources have done their own testing. While a tremendous number of commercial results are available on the internet, I have restricted the following list to those which did not favor a single commercial vendor, and instead looked at either several manufacturers, and/or several different lighting systems, to make their comparisons.
Cornell University has done quite a bit of LED research, with several publications on the subject. One of the most relevant for our purposes was a review of LED lighting in a greenhouse environment, compared to other HID light sources. A write-up of that research project and findings is available here.
The Urban Vertical Farming Project, while not a university project per se, was conducted to determine how LED lighting could assist with lighting issues in what is one of the more challenging grow conditions: urban vertical agriculture. In this form of agriculture, the plants are not only grown indoors, but in vertical columns, such that light must be supplied from the sides rather than the top. Natural lighting is rarely enough. This project looked at how well LED lights could provide the various lighting requirements under that scenario. Their write-up is available here.
Finally, the University of Alaska-Fairbanks has been working with LEDs intensively for a number of years, as have a few commercial growers nearby. Growers in arctic climates have the three-fold challenge of raising crops in low-light or no-light conditions for much of the year, dealing with extreme cold for much of the year, and finding ways to make an operation not only practical but profitable despite higher-than-average energy and infrastructure costs. So LEDs have really been put through their paces in UAF's research. Several PDFs discuss that work:
As we become aware of other sources of reliable research, we'll share them here.
These are the newest commercially available HID lighting source on the market, and as such they are fairly hard to find. Specialty shops and LED manufacturers are generally the only two sources for these lamps. Happily, these sources are almost always willing and able to do mail order. LED lamps are also very lightweight, not needing the heavy ballast required for metal halide and high pressure sodium lamps. If you already know that you want LED lighting for your growing needs, doing a Google search on "LED grow lights" will help locate both local and national retailers that can provide what you need. On the right side of this page, we've listed a variety of LED grow lights from various manufacturers, all of which are available through Amazon.com.