LED Trial with Critical Jack

Soft Secrets
17 Aug 2011

Light emitting diodes are electroluminescent, they use small doped semiconductors to emit light. They have two leads, a positive and a negative. When current is applied from positive to negative, they produce light. The individual diodes are usually one to five watts each, with several wired together to make a single light fixture. For example, a single 30w LED light might be manufactured from 30 x 1w diodes, or 10 x 3w diodes.

LEDs create about the same amount of light per watt as fluorescent lighting. An advantage LED lamps have over fluorescent lamps is the ability to project specific wavelengths (colors) of light. Chlorophyll uses light with wavelengths primarily from the red, blue and violet bands. Green light is reflected back away from the plant, which is why the plant appears green. A fluorescent lamp will use its power to broadcast light in many colors. This includes spending some energy on producing green light.

However, if green light is not used by the plant, then that energy is wasted. LEDs are made to emit specific wavelengths, so by using red, blue and violet lamps, energy is not spent on creating green light. A higher percentage of the energy spent is converted into light that the plants can use. Prototypes of LED grow lights disappointed a lot of early adopters. The first units arrived on the scene with a lot of hype and a high price tag; they either didn't work, or didn't work well.

Today's units still come with the hype and the price, but I was curious if the advances in technology had advanced to the point where they were a viable alternative to HIDs and fluorescents. The unit I tested is a commercial 104w combination of one- and three-watt LEDs from the Netherlands. It seems well built, and being mostly solid-state, is more shock resistant than glass lamps. It runs much cooler than HID lighting, and at least in theory, should last longer without needing bulb or part replacements. However, it is not an inexpensive unit to purchase: retail price runs in the same ballpark as a budget HID magnetic coil 1000w, ballast, bulb and socket.

The 1000w light would generate a lot more waste heat, would require more electricity to use, and would add the expense of bulb replacement, but may be more appropriate if these factors are not a concern. The self-contained unit is heavy for its size, but was easy to set up in a small space. To ensure that the plants were from quality genetics, Dinafem's Critical Jack seeds were used. The plants were grown in perlite with small plastic pots as containers, in an indoor vented closet.

The testing took more trials than expected, and the learning curve on use was steeper than it appeared. My experience so far with LEDs has shown them to be unforgiving of errors, and as such I would not recommend them as a good choice for novice growers. Trial one ended prematurely due to low temperature issues. The LED unit runs much cooler than traditional lighting, and as a result the plants suffered from the cool temperatures in the space. The lower waste heat of the LEDs could be useful in conditions where excess waste heat is a problem.

Trial two also ended prematurely, due to a combination of complications from having the light too close to the canopy, and nutrient uptake problems. Plant transpiration under the unit was reduced, and as a result, water moved through the plant at a slower rate than I am used to. Since I used perlite as a growing medium, over-watering wasn't an issue, but when using LEDs over soil, be careful of over-watering. The third trial successfully completed from seed to harvest without incident. Four seeds were put in to sprout on December 17th. They sprouted normally, and early growth was compact and vigorous.

Internode length was shorter, and foliage was denser than my experiences with HPS or fluorescent lighting. Lighting was switched to 12 hours on/12 hours off at 130 days from seed. The spacing of the branches was still very short, and the plant was very bushy, but it was also small for its age. Gender declared itself as normal (being feminized, it declared female); bud development was very tight. Overall, the plant appeared to be a miniaturized version of a much larger plant. During mid flowering, to ensure the plants did not suffer due to crowding, three of the plants were removed.

The plant finished in 55 days (just under 8 weeks). Bud development started very slow, but picked up dramatically in the last couple of weeks. Wet weight was 2.7 ounces (75 grams) which trimmed and dried to .7 ounce (20 grams) of nice smoke. Start to finish it took 185 days, and final harvest was 20 grams for a GPD (grams per day) of .108. Calculating the GPD for each harvest will allow a gardener to compare the success of grows even if the number of days taken for each is different.

Compared to the GPDs from other tests, the 104w LED unit performed better than a 250w HID, but not as well as a 400w HID. The Critical Jack has a woody aroma with subtle notes of lemon. The smoke is sweet tasting, smooth with a hint of bite, and has a very pleasant exhale. It delivers a nicely potent hit, and leaves a nice warm afterglow. LEDs have come a long way since they first hit the market. For use in stealth cabinets or in a location where heat is an issue, they are worth taking a look at - if the cost of purchasing the unit doesn't break the budget.

I can confidently say that it is possible to grow good weed under a well-designed LED light, and that, watt for watt, they perform better than HPS or fluorescent technologies. I have no doubt that a 400w LED array could easily outperform a 400w HID light. However, at current market prices, 400w of LED array is substantially more expensive than 400w of HID lighting, so initial cost may be an important consideration. Peace, love and puka shells, Grubbycup

Soft Secrets