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What’s the Perfect CMH distance from Canopy? Read to Know!

Putting up a grow light in your grow room or tent is only one part of the equation. In indoor gardening, hanging the light at the optimal height is key for supporting healthy growth and production. When growing plants indoors, it is critical to choose light and on what distance it should hang. Here, we are recommending CMH grow lights. But for these lights too, it is essential to provide your plants with an adequate CMH distance from Canopy of plants.

Let us also warn you that Poor yields and sick specimens are just around the corner if your plants don’t get enough light. Distance of the light source also matters too. But getting this right isn’t always easy. The optimal distance is determined by a variety of factors, including the type, quality of your light, and the age of your plants. Here, we are describing everything! But first, let us introduce you to one of the best grow lights- CMH.

What is CMH?

In 1960, CMH or Ceramic Metal Halide grow lights were invented and are now referred to interchangeably as “Light Emitting Ceramic (LEC)” because they use the same technology. CMH grow lights, like the sun, have a broad and consistent spectrum that produces powerful light output with UV. This light allows plants to grow to their full potential.

The ceramic emitter component distinguishes a CMH lamp from an MH lamp. Because of this ceramic tube, the ceramic metal halide grows light that can withstand much higher temperatures.

If the light does not fall properly on plants, then several complications arise. These can also be termed as Light stress signs.

What Are The Signs Of Light Stress?

When the heat and intensity of the light are allowed to persist, they can cause significant damage. If we talk about distance, it only takes a few centimeters for your grow light to cause stress on your plants. These stressors, known as heat stress and light burn, can result in the following symptoms:

  • The edges of the leaves are drying, curling, and cupping upwards.
  • Yellow leaves or leaf tips that deteriorate from the top down
  • The leaves become crispy and fall off.
  • The green color of the leaves fades and they appear bleached.
  • The buds of the plant appear “burned.”

If you notice any of these symptoms, especially on the leaves closest to the light source, it’s time to do something about lighting.

Why Does Grow Light Distance Matter?

We know that light intensity is inversely proportional to distance squared. It means that a small change (away) in the CMH distance from canopy can result in a significant difference in light intensity.

If you’ve ever grown plants, you’ll know that your plants require a lot of light. Simply put, more light equals more productive plants which in return gives higher yields. However, hanging your lights too close to your plants can cause problems. The key here is to find the ideal CMH distance from Canopy that promotes optimal yields while not jeopardizing plant health. And the fact that there is no general recommendation for the best (and safest) grow light distance complicates matters.

But, a safe distance isn’t as important with some types of grow lights, such as CFLs. You can position your grow light as close to your plants as possible. Other lights, such as HID grow lights, emit a lot of heat, so there must be enough space between the canopy and the grow light. Then, there are LED grow lights, which produce a lot of light while not getting too hot. Furthermore, the optimal distance is determined by the strength of your light and the stage of growth of your plant.

What’s CMH distance from Canopy?

No matter what type of grow light you use, you should hang it at the optimal distance from your plants. Always look for the best lighting sources and CMH is one of them.

CMH lamps are recommended for universal installation above the canopy without causing bulb damage. As the light distribution is so intense, the 315w CMH footprint coverage is greater than that of MH and HPS bulbs. With this intensity comes heat, which necessitates the 315W CMH grow light distance at least 2ft from the canopy and the 630W CMH light at least 3ft from the canopy to cancel the heat effect.

Let’s have a look at their coverage rates now. The 315W CMH lamp has a coverage range of 3ft x 3ft to 4ft x 4ft while the coverage of the 630W CMH lamp ranges from 5ft x 5ft to 6ft x 6ft.

How close should CMH grow light be to plants?

We know the majority of you are using CMH grow lights for your indoor plants. Unfortunately, those are the most difficult to estimate an ideal hanging height for. You must be wondering what is the perfect CMH distance from canopy. First, let us tell you that CMH is a deceptively powerful light. The light appears dim, and it does not appear to be very hot, but it has the potential to scorch the plants. As a result, whenever you start using a new light, you should keep a close eye on your garden until you get a feel for the ideal grows 630w CMH height above plants.

As with the HPS and MH lights, a hand test should be performed to determine how hot the light is.

Hand test

The hand test is a quick way to see if your plants are getting too much light. This one is quite simple. What you need to do is to place your hand beneath your light to measure the CMH distance from the canopy. It should be safe for your plants if you can comfortably keep your hands there for about 30 seconds without them getting hot. Of course, you should still keep an eye on your plants because this method isn’t always reliable, but it can help prevent major stress or burning. You can even determine 630w CMH height above the plant by this hand test method.

After the hand test, you can estimate the distance needed between plant and light. However, a CMH bulb should typically be hung two feet above the canopy of your plants. You should hang the CMH light at the recommended distance.

Keep an eye on your plants and turn off the lights if you notice any signs of bleaching (i.e. the leaves begin turning white). If the plants are fine, move them closer until they begin to bleach the leaves. Then slowly back them off until you’ve reached your ideal height. 

How High Do I Hang CMH Lights?

You must be wondering How High Do I Hang CMH Lights? Well To determine the best hanging distance for ceramic metal halide grow lights, repeat the hand test described above. Begin by suspending the ceramic discharge MH lights two feet above the canopy. This is the typical hanging distance for a 315 watt CMH light (which is most of them). You can start the 630 watts (double bulb) fixtures at the same distance as the others.

Should You Keep Adjusting The Hanging Height Of Your Grow Lights?

Yes! Whatever type of grow light you use in your grow room, you should use an easily adjustable grow light hanger or chain to change the CMH distance from canopy depending on the stage of growth, the height of your plants, and how they respond to lighting in general.

When your plants are growing quickly, it’s possible that your lights will need to be adjusted every day or two. This is critical if you want to promote healthy growth at all stages.

CMH distance from canopy
Proper light is necessary for proper growth.

Tips For Calculating CMH distance from canopy

Aside from consulting with the manufacturer of your grow light to determine the ideal hanging distance, there are other methods too which you can use to find the correct CMH distance from the canopy:

Use a lux meter or a Par meter

Lux (or lumens) is a unit of measurement for the intensity of light. However, keep in mind that lux isn’t a very good way to measure light as it relates to plants. This is since lux measures light intensity as seen by humans, rather than how plants use it.

A PAR (photosynthetically active radiation) meter would be required to precisely measure the amount of light used by plants. On the other hand, they are quite pricey, but they provide the most accurate reading of the correct distance of 315 CMH for veg.

However, a lux meter, which can be obtained for a low cost, can provide a rough estimate of the light intensity in your grow room. Furthermore, keep in mind that a lux meter isn’t appropriate when using LEDs that emit purple light. The recommended lux levels for each major stage of growth are listed below:

  • Veg: 15,000 lux (minimum) to 40,000 lux (maximum) (max)
  • Flowering: 35,000 lux (minimum) to 60,000 lux (maximum) (max)

Constantly look for signs of light stress

Without a doubt, general observance is a valid method for determining the optimal distance between your weed and your lights. Light and/or heat stress can be indicated by bleached, curled, yellow, dry, or crumbly leaves, especially those closest to the light. If you notice any of these signs, move your lights away from your plants and see if the situation improves.

Check your equipment

Grow lights gradually lose their intensity as they age. HID bulbs, for example, have a lifespan of about a year, while LEC lights have a lifespan that is roughly twice as long. Because their performance deteriorates, it’s critical to keep your lights in good working order, especially if you’re calculating intensity using manufacturer figures. Remember that these recommendations are for new lights that are at their peak performance. As a result, replace your HID (MH and HPS) bulbs on a regular basis—at least once a year. Only then will you be able to fully utilize the intensity of your light.

Conclusion

All in all, to get the most out of your plant, you should maintain your 315w CMH grow light distance to support healthy growth and production. Don’t be intimidated by the various types of grow lights or technical terms, especially if you’re still new to indoor cultivation. You can find forums full of enthusiastic growers who will gladly give you advice about CMH distance from canopy based on their own experiences. This is, without a doubt, the best way to get assistance with anything related to hanging height for CMH. Hope this article helps you determine the ideal distance from the canopy.

FAQs

How far should CMH lights be from plants?

As with the HPS and MH lights, a hand test should be performed to determine how hot the light is. After that, you can estimate the distance needed between plant and light. However, a CMH bulb should typically be hung two feet above the canopy of your plants. As the light distribution is so intense, the 315w CMH coverage is greater than that of MH and HPS bulbs. With this intensity comes heat, which necessitates the 315W CMH grow light distance at least 2ft from the canopy. The 630 watts CMH light coverage is high so you should hang it at least 3ft from the canopy to cancel out the heat effect.

How close is a 315 CMH?

As the light distribution is so intense, the 315w CMH coverage is greater than that of MH and HPS bulbs. With this intensity comes heat, which necessitates the 315W CMH for veg grow light distance at least 2ft from the canopy and the 630W CMH light at least 3ft from the canopy to cancel out the effects of the heat. The 315W CMH lamp has a coverage range of 3ft x 3ft to 4ft x 4ft. The coverage of the 630W CMH lamp ranges from 5ft x 5ft to 6ft x 6ft.

Is CMH good for flowering?

CMH bulbs are also excellent for flowering, but not as well as HPS bulbs. They are, however, much better at vegging, making them the ideal full-cycle bulbs. CMH lamps are typically more expensive than HPS lamps, but they compensate by having twice the usable lifespan.

Is CMH full-spectrum?

As CMH grow lights produce a full spectrum of light, some UltraViolet and InfraRed light will be produced. These parts of the spectrum are extremely beneficial in combating pathogens such as mold and mildew, as well as some pests. CMH grow lights promote healthier plant growth than LED grow lights.

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I am a graduate in Agriculture Sciences and have been doing gardening for over 7 years. I am also a professional and certified Article & Blog Writer. I am happy to share my years of experience in gardening with all of you through my writings. In addition to this, I do extensive research on every topic to enrich readers with valuable knowledge.