Guide To Getting The Best Lights For Growing Weed

led lights for weed

It can be quite intimidating for the first time buyer who is wanting to purchase indoor grow lights for cannabis. It is especially confusing as LED grow lights have their vocabulary like UV, full spectrum, PAR, light spectrum, IR, etc. Because of this, I’ve decided to write quick guidelines on what to look for when you are wanting to purchase LED grow lights. Below, are the question you should ask when buying LED grow lights.

1. How Many Grow Lights Should I Buy?

This is the number one question that potential LED grow light purchasers act. First of all, there isn’t an exact formula that you can use to answer this question because the number of grow lights needed depends upon the size of your cannabis plants, plant strain and more importantly how big is your grow space or grow tent. Also, under most circumstances, you can buy a more powerful LED grow light and not have to worry about buying more than one light. Getting the correct of lights though is essential because if your cannabis plants are too close to the grow light, they’ll at best not grow up to their potential and at worse your plants will be burn.

So, below are guidelines of what you should look into, in order to determine how many or how powerful a grow light you should purchase:

Check The Owners Manual
: The first thing to do is to look for “coverage area” in your grow lights owners manual. It will say for example 4’x4’, which means that this lamp will cover a four foot by four foot growing area. However, LED grow light manufacturers tend to over-inflate the coverage area. So, take their advice with a grain of salt.

  • Watts Per Cannabis Plant: The guideline is 50 watts per plant. However, this is not the preferred method because plant sizes vary, and also different cannabis strains may require more or fewer lights.
  • Growing Space Size: Because different strains of cannabis may have different lighting needs you should use the square feet of your grow tent or grow area as a baseline where you calculate the number of square feet by 30 or 40.

For example, if you have a 4’x4’ grow tent, you would need to have a 640W lamp. (Based upon the 40W per square ft.)

This calculation is done using simple math that is illustrated below this article. (fig. 1)

4’ X 4’=16 Sq Feet
16 Sq Feet X 40 Sq Feet=640 Watts

  • Check Reviews: For the more popular grow lights you may find guidelines from verified purchasers of your grow light  in either product reviews or forums.  

Tip: In most cases, using more watts (buying more lights or higher-power lights) will result in you having a higher yield, and using fewer lights will mean a lower yield.

These above guidelines are just “Guidelines” and aren’t set in stone. So, naturally, based upon your results, you should either purchase more grow light, buy a grow light with more watts or move your grow lighter either closer or away from your plants. However, with time and experience, you should be able to buy the appropriate number of grow lights for your grow tent.

2. How Far Do You Need To Place The Lights From Your Plants?

This is an important question because your plants may burn if the grow lights are too close to the plants, and if they are too far from your cannabis plants your yield will be reduced. Keep in mind, the distance needed from light to plant does vary by grow light manufacturer. Many manufacturers though will give you specific guidelines on the correct placement distance. So, first, read the owners manual or contact the grow light maker.
However, if that is not possible or if they won’t give you a straight answer, you should look at the following chart below:

3. Are Your Grow Lights Full Spectrum?

Full spectrum LED grow lights are the preferred choice for most growers as they are designed to closely mimic the sun, by including every light color that needed for plants to photosynthesize. Full spectrum lighting also provides sufficient light for cannabis in both the vegetative and flower stages of growth. Full spectrum grow lights, in theory, makes it unnecessary to use either red or blue LED lights alone. 

Buyers Tip-Some, full spectrum grow light manufacturers don’t have a separate veg and flower switch that will allow you to use either red or blue lighting exclusively. So, if you desire to use lighting that's tailored explicitly for either vegetative or flowers, you will need to invest in a LED grow light with a veg and flower switch or buy supplemental red or blue led grow lamps.

4. Does The LED Light Have A High-Quality Semi-Conductor Chip?
The semiconductor chip is a crucial part of the LED grow light. This chip turns electricity into the light used to grow your plants. If you have poor quality or a low watt chip your LED light won't be as bright as it should. Therefore, you should purchase at least a three watt LED chip for your grow light.

5. Are You Going To Be Growing Seedling, Plants, or Flowers?

Full spectrum lighting, as it is closest to natural sunlight, is the preferred choice for many buyers who are growing their cannabis from seed to harvest. However, if you are purchasing plants that are ready to be planted, you may though want to try exclusively using either veg grow light ("blue") or a flower light ("red") for your cannabis.

However, many grow led light companies do not have a veg and flower switch, which allows you to switch between either red light or blue light. A veg and flower switch feature may cost more. However, if you purchase LED lights with this option, you’ll be able to more easily experiment and find out if exclusively using blue or red lighting is worthwhile of whether or not you should just still with a full spectrum light.

6. Does It Have A Daisy Chain Cord?
A daisy chain cord allows you to connect different lights. Therefore, unless you are a hobbyist grower, or have minimal space, you should at least consider only buying LED lights, which include a daisy chain cord.

7. Does It Have An On and Off Switch?
The goal of grow lights is to essentially trick the plants into thinking that the LED grow lights is the sun. So, just as outdoors most plants aren’t subject to constant sunlight, you will also not want to keep your grow lights lights on 24/7. So, it is best that you purchase a grow light that either has its timer or you'll need to buy a timer separately as you don’t’ want to take a chance of forgetting to either turn off or on your grow lights.

8. Does It Have a UV LED Grow Light?

Ultraviolet light (”UV”) is the invisible light that is responsible for causing sunburns. Many growers believe that exposure to UV light will result in cannabis plants having a higher THC count. The theory behind this is that plants, just like humans, get sunburns. Plants, specifically cannabis plants, as a defense mechanism against the UV lighting, react to UV exposure by producing resin and in theory more THC.
UV LED grow lights exposure has not been scientifically proven to increase THC potency in cannabis. UV lighting is not included in some grow lights and you will likely pay more for UV lighting. So, it is ultimately your decision on whether or not you should, pay extra, to purchase led grow lights with UV capability.

9. Does It Have A Warranty?

Most grow light manufacturers have at least a three-year warranty. However, many warranties only allow a refund for 30 days, and you will be required to also pay for shipping after the 30 days has passed. Additionally, if it is a Chinese, led grow light, it can take a month or more to ship and get back a faulty grow light from the manufacturer.
So, if you are growing cannabis commercially, you need to check out the warranty carefully. And if the company does not have a local headquarters, where you can ship and get a replacement, you should consider buying another light or buy a back up LED grow light.

Grow Light

Watts

Recommended Distance​

From Plants

240-400w

16-30”

450-550w

24-26”

600-850w-

26-42”

Grow Light Distance Chart

Fig. 1

Click the following link for our  Best Full Spectrum LED Grow Lights Review

FYI

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