Cannabis Growing Tips: How to Set Up Indoor Grow Lights

Too much light can harm your cannabis plants just as much as too little. Learn all you need to know about light as it relates to cannabis and how to properly set up grow lights for a big indoor harvest.

Learn to evaluate and position your cannabis grow lights for maximum results.

Three Common Types of Modern Grow Lights

Contemporary indoor cannabis growing typically involves at least one of three artificial light sources: HIDCFL and LED. Generally speaking, growers use a combination grow light. There are other older lighting technologies, of course, but they are almost all "Betamax" lamps. This blog will focus on the lighting most commonly used by cannabis growers in the 21st century. We focus on actual grow space recommendations without relying on pseudo-scientific statistics.

HID or High Intensity Discharge lamps have been the go-to choice for indoor growers from beginner to professional growers since at least the early 1990s. Over the years, lamps have become more efficient, ballasts have become digital, and reflectors have become bigger and better. HID growers firmly believe that lumens are the only statistic that matters when it comes to lighting output.

Certainly, CMH or Ceramic Metal Halide lamps have come along, and the 315WCMH bulb is impressive, but it is a fairly expensive upgrade from a standard MH or Metal Halide lamp. Plus, the 315WCMH doesn't perform as well as a high-end dual spectrum/agricultural 600 watt hour High Pressure Sodium lamp. Likewise, CFL has shown some promise, but it has always run farther than the tried and trusted HID.

LEDs or light emitting diodes are a new groundbreaking technology that promises to end the reign of HID in cannabis cultivation. The latest generation of LED systems can now produce higher quality cannabis than regular HID equipment. PAR or photosynthetically active radiation is the most important metric considered by LED enthusiasts.

It is best not to get too caught up in all the new light measurements and modified light spectrums. Keep things simple. Think of light in terms of watts and electricity costs. Next comes the question, "How much power does the light consume?" followed by "How much heat does the light produce and how much light does it emit?"

Old fashioned: HID lamps

In common and respectable drug-using terms, HID has taken on some new fancies, but the core principles of growing cannabis with this artificial light remain the same. MH is for vegetative growth and HPS is for flowering. While dual spectrum HPS lamps are a welcome alternative, it may even be better suited for autoflowering varieties.

400W and 600W bulbs are best suited for growing cannabis indoors. The lamp needs to be hung horizontally. The optimal light height or OLH is 30-50 cm above the canopy of the plant. This means carefully securing the reflector to the ceiling or roof of the grow tent using a simple roll-up hanger or rope ratchet.

It is best to use a fixture that can be easily adjusted and repositioned as the plants mature and grow taller. However, seedlings and cuttings may find 600WMH too strong and a distance of 60 cm or more may be more appropriate.

Don't mess with light rails unless you have an engineering certificate. Horizontal bulbs mounted in clean, open reflectors will not wobble, and fixed lights are the standard of professional cultivation. The ideal situation is to use a large reflector, or squeeze into the largest possible growing space, and use it extensively over the entire area.

Glass filters, lamps, and air-cooled lamps are expensive. So cold tubes are really only suitable for closets because their reflective characteristics are the worst of all reflectors on the market. Adding more lamps and fans means higher electricity bills.

Lighting and growing space

Generally speaking, 400-600 watts per square meter is enough light for a home growing project. Commercial growers may increase the power to 1000 watts for the highest yield. Packing as many lights as possible into a grow room is not a shortcut to a good harvest. More HID lights mean more light, but it also means more heat. These babies are hot. 250W lights are only for micro growers.

The only advantage a 250W light offers is that the tops of the plants can be 20 cm closer to the bulb. The heat output is much lower than a 600W, but the light won't penetrate as far. Limited light will reach the lower branches of taller plants.

Simply adding an extra 600W HPS can significantly increase the temperature of the grow room. Investing in an upgrade to your grow room is often a lower cost, more effective solution. Maybe cover the walls with mylar, or upgrade from magnetic ballasts to dimmable digital ballasts, or always go with LEDs.

How many plants?

The answer is more or less as the grower likes. You can put 16 cannabis plants in an 11-liter square container in a 1-square-meter grow space in a SOG. Or, a grower can use the ScrOG method to grow one large plant in the same space. Either way, the output is comparable. Again, it all depends on how you utilize the light and the grow area.

Supplementing CFLs

CFLs or compact fluorescent lamps are very effective as a replacement for MH bulbs in the cool white light spectrum. A 250W CFL can provide contrasting results to a 400W metal halide lamp. This is achieved by hanging the CFL 10cm above the plant canopy. CFLs run cool and can be very close to the plant without burning the leaves. In addition, CFL lamps only slightly increase the temperature of the grow. This makes CFLs ideal for seedlings, cuttings and use during vegetative growth. CFL lamps are sometimes the only option for micro growers.

Unfortunately, CFLs have neither impressive lumens nor standard output figures. Worse still, CFL lamps are not very effective for flowering cannabis. Marijuana plants require stronger light than CFLs can provide when flowering. During the flowering stage, CFL lamps are expected to gain light yield and loose buds.

Next Generation LEDs

The latest LED systems have finally reached the same level as traditional HID lighting systems. The situation is now similar to when flat screen televisions first appeared at the turn of the century. The benefits and advantages are obvious. However, the limiting factor is the high price of the leading manufacturers.

High performance LED kits with 350-400W to better than 600WMH and HPS configurations with full spectrum arrays are not cheap. There are a few models that really can do it all. The best systems run very cool and are very economical in the long run. Hanging distances vary widely, so buyers should be careful and make sure to check the manufacturer's instructions.