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#4: How much light do your plants need and what is the best type?

October 08, 2018 9 Comments

#4: How much light do your plants need and what is the best type?

There are so many awesome things about being Canadian!  Getting only 1 harvest a year outside is not one of them.  But with the right type of grow light and the right size light you can have happy healthy plants and great yields year round.


GrOh Canada’s Recommendation

We recommend that hobbyist growers start with a 4’x2’ or 4’x 4’ tent, using LED lights. Keep reading to find out why.

How much light do you really need?

Light is basically the food that your plants need for big yields. Your plant turns light into energy through photosynthesis, and this energy is what fuels the vegetative and flowering growth. Flowers that are exposed to air and bright light will tend to build up. Even if everything else in your grow is perfect, without a strong, intense light your yield will just be average.

As a beginner grower you want between 50 – 75 watts (w) of light per s/f of “canopy”. From our last blog you will remember   

  • Canopy = the amount of green space that your plants consume (e.g. leafs, buds, stalks) inside your tent;
  •  Keep 20% of your tent space free from plants so you have enough room to interact with your plants (i.e. fill up to 80% of your tent space with canopy)
  • 1 square foot (s/f) of canopy = 1 ounce of dry bud 

An experienced grower can go up to 100w per s/f to maximize their yield but you will need to keep a close eye on your plants to ensure that you aren’t burning your buds. Lower than 50w of light per s/f of canopy and you will be leaving yield “on the table”.

Light strength/Tent size guideline

  Tip: The lights in our GrOh Canada kits are at the top of this range to ensure big yields!

Pro’s and Con’s of the Different Types of Light

Now that you know how strong your light needs to be, you’ll want to figure out what type of light you want to use. The most popular lights are: LED Grow Lights; HID Grow Lights, or T5 Grow Lights. There are pro’s and con’s to each that you need to know about.

LED Grow Lights                                                                          


LED grow lights are quickly becoming the go to grow light for recreational growing for a number of reasons, and the technology is improving all the time.


Pros of LED Grow Lights

  • LED’s give an intense spectrum that can’t be beat, including implementing UV and IR wavelengths that are great for resin growth and plant strength.
  • LED’s are very efficient to run compared to other types of lights which keeps electricity costs low
  • Very simple to setup - just plug them in and start growing.
  • Usually have built-in cooling so they emit very low heat.
  • Have great canopy penetration to reach the leaves at the base of the plants.

Cons of LED Grow Lights

  • Higher initial investment than other types of light – buying LED’s can cost up to 25% more than an equivalent fluorescent lights.
  • Because of the intense light LED’s emit, they need be kept about 18” away from plants; or up to 30″ for bigger models. This means you need a higher tent.


When shopping for LEDs, make sure they contain full spectrum lighting, including green or white light. Plants grown without at least a tiny amount of green or white light are very prone to nutrient deficiencies and simply don’t grow as well.

GrOh Canada loves LED lights because they are easy to use, have low electricity costs and are more forgiving than any other light. Perfect for new growers!


T5 Fluorescent Grow Lights 


Fluorescents are popular because they make efficient and pleasant lighting for humans, and also work great for herb gardens and other types of low-key indoor gardening without using a lot of electricity.

Pros of Fluorescents

  • Affordable
  • Low running cost and heat emission (unless you have a lot of them packed together in a small space)
  • Great light spectrum for growing your 4 recreational plants
  • Since lights can safely be kept just a few inches away from plants, they’re a good choice for short spaces

Cons of Fluorescents

  • Smaller yields per watt than the other types of grow lights – you can expect to yield about half as much as you would with other types of light.
  • Fluorescent light doesn’t penetrate far down into the plant so they are best suited to plants that have been trained to grow short and flat. 


High Intensity Discharge (HID) Grow Lights


HID’s give you a light closer to the spectrum of the sun than any other light, which plants absolutely love. But like the sun, they run very hot so you will need a heat control system when running these lights.

Pros of HID’s

  • HIDs offer the highest yields per watt of light.
  • More affordable purchase price.

Cons of HID’s

  • HID’s generate a lot of heat. You will always want to put the bulb in a hood with a cooling system to maintain the heat in your tent.
  • Significant setup is required as a result of the cooling system required.
  • More parts – HID lighting requires at least a bulb, fixture, an external ballast and an extra cable if you don’t count the exhaust systems parts, too.

Next Blog Post: Our next blog will discuss Airflow for your Grow Tent.  Stay tuned! 

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October 12, 2018

Definitely for recreational plants

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