Marijuana flower growing under LED lightAn often heard slogan amongst Dutch growers is that 'you can only take it seriously when regular greenhouse growers use it.’ Well, since Philips, as one of the leading forces in the LED revolution, has marketed its GreenPower LED lighting for professional growers, a growing number of them are using the technology.

Note: so far the GreenPower LEDs are not meant to replace HID lighting but intended for multi layer cultivation, where trays of small container plants are mounted in many layered racks. Quite a different situation from the typical grow room. So it remains to be seen, the tried and tested slogan applies to LED lighting.

For some years now LED (Light Emitting Diodes) growlighting has been a somewhat difficult subject to get a grip on. What certainly hasn’ t helped the LED cause are the outrageous claims producers use to promote their product, like 'Our 90 watt LED unit replaces a 400 watt HPS’. If you were a gullible early adapter, by now you’ll surely have turned into a rabid non-believer. A lot of people seem to be wary about traditional high pressure discharge lighting because of soaring electricity bills, heat signature and fire risk, and the trouble it often takes to keep temperatures within acceptable limits.

There's also the current tendency to use smaller grow spaces, such as grow tents, adding to the issue of temperature control. 'The physics is just so elegant compared to tungsten or fluorescent (a 1930s technology) that I really want it to work’ one forum member mentions. That seems to sum up the feelings of quite a few growers who are enchanted by the idea of LED lighting. I know, because I was one of them.

LED powered weed budsI was offered the opportunity to test two LED fixtures in a converted closet that I just couldn’t get to perform properly using HPS bulbs. Getting rid of excess heat during the summer appeared to be an impossible challenge - at least when I didn’t want to rattle the neigbours out of bed with the continouous drone of a huge exhaust fan. Even though 'those in the know’ warned me that LEDs are not a serious alternative to traditional grow lighting, I was determined to prove them wrong. Didn’t the guy who offered me the test models seem a decent down to earth kind of chap? But even he couldn’t produce photographic material that would give undeniable proof of the effectiveness of his product.

Nevertheless I started out wanting this experiment to succeed, preparing my grow space to perfection. Well, what happened? For sure, heat ceased to be a problem, even during the hottest days of heat in the summer. But solving that problem was replaced by some new issues. In winter low temperatures became a problem, the absence of heat lowered transpiration, and thus irrigation needs, changing nutritional values at the same time.

In spite of having to cope with a completely new set of parameters, the 300 watt LED unit resulted in healthy vegging and some very decent bud, but the yield was quite disappointing: not even half a gram per watt. Then there was the extra time it took me to get the plants to mature nicely. Flowering took at least two weeks longer than I was used to (other LED growers have reported exactly the opposite by the way). But that was two years ago. LED technology moves at lightning speed, so maybe my experience was outdated by new developments. Let's find out...

THC-bleeding Bud Shots, Please!

LED Cannabis Grow BudsOn forums there’s a lot of discussion, tech talk and even LED grow reports, but you rarely - if ever - see a grow report that’s neatly wrapped up, showing resin-bleeding budshots and giving the figures, preferably grams to watts, comparing yields to previous grows in the same space.

One explanation for the reserved wait-and-see attitude of many potential users is the price issue: per watt even the cheapest LED lighting is several times more expensive than HPS’s, even counting several replacement bulbs. 100 watt LED kits sell for around 220 euro ($300) and up, 325 watt models for around 730 euro ($1000), while 600+ watt models set you back 1100 euro ($1500) or (much) more. Though production of LEDs isn’t that expensive, big money is invested in development, especially the search for more powerful LEDs, so it may take some time before prices get to competitive levels.

Even when you include the potential savings on electricity, another issue may ruin your optimistic calculations: quality. Reliability, especially when dealing with cheaper brands, seems to be a recurring issue. These are problems that are usually difficult to solve as the sellers/producers are usually located in China. Shipping a broken fixture back to China may well cost you more than the item you’re shipping. So that other argument in favor of LED lighting, longevity, proves a dead letter in quite a few cases. Then there is the argument that puts most weight in, literally. Maybe theoretically most of us would like to reduce our ecological footprint, but not when it comes at the cost of yields that compare unfavorably to what we’re used to.

Beyond Doubt

Some enthousiasts are way beyond doubt and are convinced you can already have similar or even better results using LEDs. "While my 250w LEDs aren't big enough to do as much as a HPS 1000w, they sure do grow buds the same size as I've had from my bigger room using HPS,'' says one grower who uses a Magnum Plus2. "LEDs just aren't a logical or efficient source of lighting for large grow ops unless using them as supplemental lighting, but it's gold for small tent growers, cabinet growers and closet growers. There's LEDs out there that can do 1gpw+. There's just good ones and bad ones. It’s up to the consumer to do research, just like buying genetics."

Another guy (medgrower) has even less reservations. "Before, I was using 2 x 400 watt HPS to grow 4 plants up to 4 feet tall at flowering. Now I’m using 3 of the 100 watt Evolution Grow Led Modules for the same grow and I’m getting better results." To put this last grower’s statement in perspective: using 800 watts of HPS lighting he managed to harvest 370 gram (14 ounce), changing to LEDs increased his yield to 440 grams (15,5 ounces).

Summing up, you can grow bud with LEDs, outstanding bud even. Just don't expect to grow the same amount with a quarter of HPS wattage. Expect to spend some time finding the right balance of parameters. In some situations LEDs may be the only reasonable, albeit costly, choice, i.e. in tiny growing spaces. Finding a reliable source is of the utmost importance. You’ll have to do a lot of homework to find out which brands are worth your hard earned money. for example has a lot of consumer reviews. Independent information is hard to find, so keep your wits about you before ordering!

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