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How Much/What Kind of Light Do You Need? (Article)


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Plex1

Plex1

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INTRO

Hopefully you’re wondering how much light you need to provide your cannabis plants, not just assuming you know and throwing them under incandescent light bulbs! In order to grow the best product, you must understand all the options for lighting your babies. If you were looking for everything about what kind of grow lights and how much light you need for your growbox, here it is all in one place! First of all, lets talk about how light makes your plants grow.

How Light Makes Plants Grow:

Understanding even a little bit about how light affects photosynthesis and makes your plant grow can benefit you. If you really don’t care you can skip ahead a little. I’m no biologist, or botanist, but basically plants use light to make energy for themselves. They use this energy to grow, and to flower. The leaves absorb different colors of light and transform it into different energy types.


The two main colors involved in photosynthesis are red and blue. Blue light is what makes your plants grow well in the vegetative state. Distance between inter-nodes (leaf sets) will be short, and the plant will be a healthy, dark green.

Here are your options for types of grow lights during vegetative growth:


  • Metal Halide Lamp
Posted ImageMetal Halide Grow Light



Arguably the best lighting choice for vegging plants. These lamps are in the right spectrum, and will often provide you with enough light for multiple plants. It is an HID system, so the heat is high as well as the cost per month (at least in comparison to cheaper alternatives–discussed later), both factors to consider. Though this is often said to be the most efficient light source for vegetative growth, high heat means more fans and ventilation, added watts, noise, and sacrificed space in your grow room due to exhaust ducting. These lights also require an external “ballast”. The best way I can explain that is it’s like an amplifier to sub woofers in a car…if you aren’t familiar with that then I can’t explain it much better. It’s basically a bulky power supply box, that gets hot. One end has a ‘computer plug’ style 120v (in the US) chord and the other receives a connection from your reflector. Some of these ballasts are dimmable, and range from around 100 watts to 1000 watt systems.

The seemingly most common and effective way to ventilate these type of lights is with large diameter, high CFM fans/blowers. Sometimes growers will have only one fan, handling ventilation and exhaust, but in larger 1000w+ systems it is wise to have a single fan extracting the heat from the lights and another separate fan for the exhaust and smell proofing–if you need it. If this is for a veg only grow area, I see no need for smell proofing, although filters do help quiet fans down and are not necessarily a bad thing either. They also make fan restrictors and controllers so you can slow your fans down if need be. In grow tents it is common for large diameter fans with little ducting or resistance to pull hard on the tent and structure.


2. HPS Lamp
Posted ImageHPS Grow Light



This will be more than enough light to grow your plant in the vegetative state, however it is not the most efficient. This will produce tall, lanky plants with long distances between nodes. The growth however, will still be quick. This isn’t really a BAD way to grow in veg state, it’s just that it cost a lot, and it’s a lot of heat to deal with for 18-24 hours of the day, especially during the summer time. These are just some things to consider if you have only an HPS light, and are thinking of vegging with just HPS. These lamps are also in the wrong spectrum for vegetative growth. They also require the same ventilation as a Metal Halide light and also require a ballast.

3. CFL, T5, etc Fluorescent Lighting
Posted ImageVarying types of Fluorescent Grow Lights



These lights are argued by some to be the most efficient lights to grow plants during veg for a few reasons. Most of us are not running large, commercial operations. We don’t have means to deal with excessive heat and insanely large amounts of energy consumption. Though fluorescent lights do not produce as rapid or as robust growth as either alternative presented thus far, when comparing energy consumption costs to plant growth and functionality between these three choices, CFL is the way that many go. CFL and other fluorescent lighting is ideal for a stealth growbox or small areas. The other major plus of this lighting choice is that you can ventilate with WAY less effort than an HID system requires. Depending on your grow area’s size, a few computer fans may be good enough for temperature and air exchange. These lights can be used for both flowering and vegging marijuana plants. For vegetative growth, it is best to use fluorescent lights with a spectrum between 4000-5500k. For flowering you want 2200-2700K. Everyone has their debate about what EXACT spectrum produces the best results, but as long as you stay within the guidelines you should be ok and figure out what works for you. Another advantage is that these lights take less space in some applications in comparison to an HID system, and they do not require bulky exhaust ducting. These lights are also considerably cheaper and easier to mount and replace than HID bulbs.

4. LED Lighting
Posted ImageLED Grow Light



LED Grow Lights are something that there is still a lot of debate about. They are relatively new to the market, and over the years have become more prominent. They are marketed to growers in stealth situations, and boast extremely low monthly costs in comparison to other systems. These lights however can cost as much or close to as much as HID lighting systems. Discussion about these lights and how well they perform is always up for debate. Some say that LED grow light costs are too high compared to their performance, and some say that they are the best alternative to veg with. A few advantages to LED lighting are increased bulb life-spans, very little heat produced, and LED lights do not contain any chemicals harmful to the environment like some other bulbs. LED lights also require little space to be mounted in. Another advantage to using LED lights is that they are able to target a more specific light spectrum (red bubs and blue bulbs), so no light is wasted due to it being in a little to unused spectrum. These lights are mainly seen in vegetative setups.

HOW MUCH Light Is Needed For My Plants?

The important thing to remember here is that watts essentially don’t matter. A 23 watt CFL bulb will serve you much better than a 100 watt incandescent bulb ever would. What is important when considering what/how much light you need is lumen output. A rule of thumb is that you need 2000 lumens per square foot MINIMALLY! This won’t have your plants exploding, or growing at any pace describable as quick. A better ratio is 3-4000 Lumens/sq foot and 5000 lumens per square foot is optimal. Lets look at what this means…

Most 600 watt HPS lights put out somewhere around 80,000 lumens. A 4′x4′ area has an area of 16 square feet (4*4). 80k divided by 16 is 5000, a perfect amount of lumens per square feet. To figure out how much light in your space, all you have to do is find the area, find out how many total lumens your lights are creating, and divide the area by lumen output. Remember that you want at least 2000 lumens per square foot!

Hopefully this article provides you with some direction as to what kind of light you want to use, and how much lighting you need for your space. The decision can be a tough one, but its not rocket science and as long as you keep the simple rules of thumb in mind your grow should do just fine!




I got this article off www.completegrowbox.com. it seems to be a cool site i think its new or something theres not much on there but something new pops up every day...


Edited by Plex1, 14 November 2012 - 06:15 AM.





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