Growing cannabis easily with LED grow lights
Expert home grower tips and advice
Growing cannabis with LED is becoming a mainstream alternative to HPS. Although the initial purchase cost of an LED is still higher than an HPS, the ongoing running costs are lower. LED produces less heat than HPS and this affects many aspects of plant maintenance and grow room design.
Growroom heat levels are totally different with LED
A 600W HPS bulb wastes around 450W (75%) of the electrical energy producing heat. A good quality LED light with a 400W power draw would produce around 200W of heat despite having the same productivity as a 600W HPS. So the best LED’s only produce about half the heat of an HPS.
For some growers that will allow a significant simplification of the grow room, such as no air conditioning in hot climates. Other growers will be able to turn down air extraction rates or use smaller extraction fans.
Traditionally many cannabis growers fight grow room temperatures, their grow rooms usually running 3 or 4ºC above the optimum point. With LED grow rooms run naturally at a cooler optimum temperature.
Why waste electrical energy to create excess heat from HPS lights only to have to pay a second time to remove the heat. Growing cannabis with LED is a better solution.
Calcium and Magnesium deficiency
LED lights usually produce much less heat than a HPS light of comparable productivity. The lower heat levels from a LED means the leaves of a cannabis plant generally transpire (evaporate) less moisture under LED compared to HPS.
The transpiration differences mean that Calcium and Magnesium ions can be less mobile under LED and this may cause deficiencies that you will have to correct with nutrient additions.
You may not notice this issue since soil (and many grow nutrients) already contain adequate levels of Calcium and Magnesium. Calcium/Magnesium supplemental nutrients are widely available in any grow shop.
Growing cannabis with LED
LED power levels have been increasing significantly over recent years, and at the same time so have the LED efficiencies. Early LED’s would convert 15% of electrical energy to light energy, now the best LEDs convert over 50% of electrical energy into light and that figure is rising.
When light levels are too intense the tips of the plants are bleached, they look white instead of green. This can be a sign to raise the LED lights higher, or to tie down the tallest branches of your plants.
Achieving the correct hanging distance
These days LED is very powerful and hanging distance will play a large role in the performance. The most common mistake when growing cannabis with LED is that the lights hang a little bit too close to their plants, especially seedlings which can suffer stress if the light is too intense for the first couple of weeks.
One easy solution is to keep seedlings in the tent corner (which may have lower intensity light compared to the tent centre), or just to raise the light and allow the plant to ‘grow into’ the more intense light as it stretches later.
Due to the lower ambient heat levels associated with LED the plants may often show a reduced need for water consumption. Remember that when watering, since inexperienced LED growers can be tempted to over water their plants which reduces root growth and subsequent plant growth. Cannabis roots need oxygenation to grow fast, over-watering them reduces root oxygenation and reduces plant growth and yield.
Taste and aroma
The best LED growers have found that the lower levels of grow room heat and the cooler tent conditions with LED is allowing more of the delicate terpenes and flavonoids to remain in the plants tissues rather than being lost to the atmosphere in a hot HPS tent.
Anyone that has opened a tent with mature cannabis plants under HPS light which has been running at high temperatures (e.g. 30ºC) will have smelled the intense aromas that flood out of the plant. Running your tent cooler with LED allows you to keep more taste and flavour in your buds instead of losing them to extracted air.
LED lights are small and convenient
Compare a bulky HPS light with a parabolic reflector to a small sophisticated LED. The HPS is hot and heavy. An LED runs cooler, is often small and slim and won’t take up all the space in your tent. People with small grow tents often find LED is the best/only way to produce cannabis.
The advantages of LED are becoming more and more obvious and this is reflected in their increased popularity. With each passing year the power and efficiency of LED continues to improve. They are less expensive to run compared to HPS and run much cooler.
The combined benefits of LED mean that HPS is increasingly looking a dated technology, producing a light spectrum that is not optimised for cannabis and too much heat. LED, by contrast, does not waste energy producing the useless orange/yellow/green wavelengths.
LED only uses energy producing wavelength-specific useful light at high efficiency and with minimal wasted heat/energy. Its a technology you will see much more of in the future.
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