LIGHTING – Replacing the sun…
Growing indoors requires artificial lighting. Common choices are Fluorescent, High Intensity Discharge (HID – Metal Halide MH, High Pressure Sodium HPS) and now LED.
Typical fluorescent lights (tubes) are usually cheap, plentiful and easy to find, and are great for seedlings, but may not provide enough lumens for serious bud production. However cannabis growers are now happily blooming under the new breed of compact fluorescents (CFLs) and special horticultural units with banks of T-5 HO (and VHO) tubes. For those with concerns about heat or high electricity usage, these lighting alternatives may very well be the only option.
HID (Metal Halide, High Pressure Sodium)
For intense growth & bloom, high-intensity discharge (HID) lighting is necessary. Using metal-halide (MH) for vegetative growth and high-pressure sodium (HPS) for bloom, yields increase greatly in comparison to CFL lighting.
Some new digital ballasts allow for swapping of both metal halide & high pressure sodium bulbs depending on what stage your grow is in. Ceramic metal halide (CMH) is another new HID contender that combines the blue spectrum for growth of metal halide with the red spectrum of high pressure sodium in one unique and efficient bulb.
LEDs (Light Emitting Diodes) emit only certain wavelengths of light and have a long lifespan (around 50,000 hours), making them a solid choice for efficient plant growth. The reason why LED growing is not commonplace is because it has been difficult to find LED lights powerful enough to sustain good growth and costs can be prohibitive. Technology has rapidly advanced in this field, 3 and 6 watt multi-spectrum diodes, now illuminate beyond that of comparable HID lights and with production increasing, prices are coming down.
Advantages to LED lighting,
- Reduce Heat and Energy Costs Up to 90 % of what you are paying now
- Non undetectable from infrared camera in helicopters and aircraft due to low heat output
- Environmentally Friendly Green Light do not use toxic chemicals like HPS and MH
Approximate Lighting Requirements (using watts)
Determining the wattage of the lighting you choose depends on the size of your space and any limitations on heat exchange. Remember that pot plants need 40 to 50 watts per square foot to thrive and reach full potential
250-watt HID* for a 2′ x 2′ area.
400-watt HID for a 3′ x 3′ area.
600-watt HID for a 4′ x 4′ area.
1,000-watt HID for a 5′ x 5′ area.
Use the specifications for HID above, then add additional 25 – 50 watts/sq. ft)
180-watt LED for up to a 2′ x 3′ area.
250-watt LED for up to a 3′ x 4′ area.
500-watt LED for a 5′ x 6′ area.
Approximate Lighting Requirements (using lumens)
The ever debated theory of the minimum amount of lighting needed to sustain growth is about 2000 lumens per square foot. Mid range is around 5000 lumens per square foot. Optimal is 7000-7500, or higher, lumens per square foot. So, for a mid to optimal range, that would require four 23 watt CFLs, for every 1 sq ft.