You often hear about growers trying to decide between HPS/MH and LED grow lights. But what about ceramic metal halide grow lights? The truth is CMH grow lights have increased in popularity over the years, and there are a couple of reasons for that.

For starters, a CMH bulb offers an even light spectrum that's good for both the flowering and vegging stages of plants. In addition, CMHs are able to pump out major light intensity with relatively low energy consumption. The end result is an effective light that's powerful enough to get your plants through different stages without impacting your electric bill too heavily.

What is a CMH Grow Light?

CMH bulb diagram showing chemical compounds in a CMH grow light. As its name suggests, a ceramic metal halide grow light uses a ceramic arc tube as opposed to a standard MH grow light, which uses a standard quartz arc tube. This stronger arc tube material helps the CMH bulb operate at a much higher pressure than the average MH bulb.

Like HIDs, CMH grow lights use a unique mixture of salts and halides to provide a ranged spectrum of light. The ceramic arc tube of the CMH bulb slows down the caustic breakdown of this mixture, creating a broader spectrum that gives plants enhanced photosynthesis for optimum growth.

CMH Grow Lights vs. HPS and MH Grow Lights

A CMH bulb offers a more natural-looking light spectrum than the bright light you'd get from an HPS or MH bulb. This light can be measured (and compared) using the Color Rendering Index (CRI). For comparison's sake: Dual-bulb CMH grow light.

The CRI of the sun is 100.
The CRI of an HPS bulb is 20 to 30.
The CRI of an MH bulb is 60 to 64.
The CRI of a CMH bulb is 90 to 92.

As you can see, the Color Rendering Index of a CMH bulb is pretty similar to what the sun offers. This means a CMH grow light will give your plants a spectrum of light that comes close to what sunlight offers naturally.

ECO Farm CMH 315W Grow Light Fixture Reflector Enclosed Kit

Features:
The ECO Farm CMH grow light kit delivers a light spectrum that's much closer to natural sunlight than typical high-intensity discharge (HID) systems. A higher temperature creating light much closer to the sun's. Being able to operate more efficiently at higher temperatures means a boost in performance, In general, it can well-cover a 4×4 grow space.,that means a bigger harvest and less cost. The lamp is optimized for the bloom phase with enhanced reds, but, because it's full-spectrum, it will produce the goods in both vegetable and flower - expect to see increased growth rates, tighter internodes, an improvement in overall vigor, and an increase in the final weight. The electronic ballast in itself has a rated lifespan of 50,000 hours. The inside of the hood is being lined with 98% reflective German aluminum and 95% textured corners. This feature allows for a more uniform diffusion of light across the plant canopy.

HI-PAR 315W SUNSTORM CONTROL KIT

Features:
This complete luminaire kit contains our ultra-durable, full-spectrum electronic 315w control ballast, a 315w CDM/CMH Horticulture lamp, and the new release HiPAR 315w Reflector. It uses the highest quality in electronic parts to ensure maximum lumens and long life. Using specialized low-frequency technology allows this package will output incredibly optimized light energy, resulting in faster and healthier growth from your plants. The 315w CMH lamp is designed for medical-grade plant cultivation. Precisely engineered to replicate the sun, it ensures that essential oil and resin production is drastically increased. The arc tube within this bulb is built with a ceramic composite and has more similar gases like an MH lamp, however, the arc tube burns much hotter and brighter, ensuring the light that comes out has more UV A, UV B, and a complete lighting spectrum.

Is CMH good for growing plants?

Ceramic metal halides are best known for their wide spectrum coverage. This means that it has the capacity to deliver a good array of light wavelengths. For plants to grow, they would need wavelengths between 400 to 700 nanometers. This range will provide the plants all the energy it needs to undergo photosynthesis.

In particular, the plants best absorb blue and red lights. The cool blue light, having a wavelength of 430 to 450 nm, is best for encouraging vegetative growth. Meanwhile, the 640 to 680 nm red light is essential for flowering and fruit production.
CMH also encompasses green and yellow light. This falls between the range of 495 to 590 nanometers. These light colors aid in the photosynthesis process of the cultivars. Also, this specific spectrum is likely reflected. Thus, it renders the green coloring of the plant itself.

It is good to note that the CMH bulb is capable of delivering both ends of the light spectrum. Making this lamp likely applicable to use throughout all the stages of the cultivar's growth.

How Far Should The Distance Be Between The CMH Lamp And The Plants?

The advantage though with CMH is that they are being meant for universal positioning. In this case, you can install them both in a horizontal or vertical position. Either way, it will not affect the light distribution and absorption rate of the plants.

What you should focus more is on the correct height and distance of the CMH lamp from your cultivars. Doing such will ensure that your plants will get the optimal benefits from the light. At the same time, it will also reduce the risk of overheating them.

In general, CMH lights should have an average of 3 feet distance above the canopy. This hanging height provides an efficient and even light distribution across the plants. Moreover, this gap is also enough to make sure that hot spots will not develop.

With regard to coverage, the area it can accommodate is dependent on the light bulb's wattage. For example, a 315W CMH bulb is likely to cover a growing area of up to 4×4. Note here that the higher the wattage, the hotter will be the heat emission. Thus, you should also expect to adjust the hanging height of your grow lights farther up as well.

Are CMH light energy efficient?

In comparison to traditional quartz metal halides, CMH lights are 20% more efficient. CMH is also better at converting electricity into usable light than other types of bulbs. Thus, the increased efficiency delivers optimal power but with lesser energy consumption.

Moreover, CMH light has a remarkable lifespan that can run up to 24,000 hours. That is more than twice longer than the 10,000 hours life expectancy of the quartz MH and even HPS bulbs. Plus, its ceramic arc tube can very well withstand high temperatures. So, they are more durable and resistant to premature breakage.

Given these superior qualities, it is quite expected for its price point to be higher too. Yes, its upfront cost can be quite steep. Then again, its energy efficiency and longer lifespan can help save you money over time. With all the benefits you can get from the bulb, most people agree that it is a worthy investment for your plants.

Conclusion

There are advantages to all grow lights. While some growers may prefer HID or LED lighting for their specific needs, a CMH grow light might be perfect for your grow room. CMHs offer large coverage at a lower wattage, a wide spectrum of light including UV light, and low power consumption.

CMH grow lights are ideal for anyone from seasoned growers with large tents to first-timers who are growing one or two plants. You really can't go wrong with a good CMH light in your grow room.