If you are planning to grow medical marijuana indoors you’ll need grow lights for plants. Plants use certain portions of the light spectrum. Without getting too far into the weeds with detail (pun intended), the most important colors for the best chlorophyll production and photosynthesis – the blue and red range, respectively – of the Kelvin light spectrum.
The Kelvin light spectrum measures the degree of visual warmth or coolness of a light source and not the temperature warmth of the light. The higher the Kelvin degree (K°) the “cooler” the light. The lower the K° the “warmer” the light.
A New Perspective On LEDs
Light Emitting Diode (LED) I stopped in a local grow store looking for some grow light bulbs. I’m starting my vegetable garden indoor this year from seeds. Long story short: they had tomatoes growing under LED and High Pressure Sodium. The LED plant was considerably smaller than the HPS plan. Everything is a trade off and not sure it’s it. LED’s are still a great idea under the right circumstances. Ideal for small spaces. Or outer spaces.
NASA pioneered the use of LED grow lights for the possibility of space colonization. The ability to grow plants in space provides fresh produce for astronauts, reduces the amount of food needed to be transported from Earth, generates and purifies oxygen and water, and utilizes carbon dioxide in an enclosed environment. NASA
Additionally, LEDs have no heat output eliminating the need for temperature control equipment like fans. There is virtually no chance of burning your plants. Or your house. LED grow lights have an estimated 50,000 hour lifecycle. LEDs have lower power consumption and can reduce energy costs. The woman at the grow store said the LED save about 30% electrical usage. LEDs are eco-friendly as they do not contain mercury.
LED light fixtures can have blue light, best suited for vegetative growth, red light for the flowering stages or full spectrum light suitable for all growth stages.
High Intensity Grow Lights For Plants:
High Intensity Discharge (HID) lights are commonly used by indoor cannabis growers because of its lumens-per-watt efficiency, spectral balance and brilliance.
To maximize production per watt a grower must keep manage the light close to the plant but not burn the plant. When using grow lights for plants the intensity of the light and the light’s distance from the plant must be considered.
Light intensity doubles for every 6 inches closer an HID is to the plant. Therefore using several small lamps with lower wattage can often cover more real estate better than one large, high wattage lamp. Some benefits include:
- More points of source light
- More even distribution of light
- Able to put lights closer to plants
The most common HID lights for growing are metal halide and high pressure sodium.
Metal Halide (MH)
Metal halide grow lights for plants produce an abundance of cooler, blue light. This light promotes leafy, bushy growth making makes MH bulbs good for early to vegetative phase of a plant. These bulbs have about 12,000 hours of life or two years of 18hour/daily use, the recommended hours for vegetative growth.
It’s a good idea to track the bulb’s life so you know when to replace it. The bulb’s gradual decline in intensity will rob your plants of needed light spectrum so don’t wait till the bulb burns out before replacing it. And keep spares on hand.
MH bulbs also come in super metal halides which go to eleven. Super metals put out approximately 15% more lumens.
Say Watt? Lumens are the amount of light a bulb produces. Wattage is the amount of electricity needed to light the bulb. The higher the watt, the brighter the light. Divide a bulb’s lumen output by the number of watts to determine the lumens per watt (LPW). A 100-watt bulb usually has 1800 lumens so the LPW is 18. LPW is an efficacy rating given to a light bulb. So when shopping for bulbs look for lights that produces more light (lumens) with less energy (watts).
High Pressure Sodium (HPS)
High pressure sodium lights bulbs emit a light that is concentrated in the orange/red spectrum. The HPS is good for the flowering stages.
HPS bulbs have approximately 24,000 hours, or five years of 12 hour/daily use, the recommended hours for flowering. HPS bulbs produce approximately 6x more light per watt of energy consumed than a standard incandescent bulb. These different light needs is another reason a two-room grow room is a good idea.
Do not try to use a HPS bulb in a MH light system or vice versa. There are conversions bulbs that allow you use an MH system and emit light similar to HPS or an HPS system to emit light similar to MH. But generally speaking, grow light ballasts are only meant for the type of HID bulb they are designed for. And definitely do not try to screw an HID bulb in a regular light fixture.
HID Light Bulb Warning: Extreme caution must be exercised when handling HID bulbs.
- Keep the bulbs clean by wiping with a soft clean cloth every 2-4 weeks.
- Be sure to let the bulb cool completely before cleaning the bulb.
- Do not touch the bulb with your bare hands! Oils from your fingers bake onto the bulb. And touching a hot bulb can cause it to break.
- HID bulbs contain mercury, a hazardous material. You do NOT want this in your house.
Lights To Avoid
- Household bulbs
- because of their low light intensity and poor color spectrum.
- Halogen
- commonly used for flood lights can get extremely hot.
- Fluorescent white
- have the proper light spectrum but are generally very low in wattage.
