Choosing the Best Lighting for Growing Cannabis

Why Does Cannabis Need Light?

There are several reasons that light is a critical and important factor to the growth of cannabis but let's head back to elementary school biology for a moment and take a look at a process called photosynthesis.

During their daylight hours, green plants like cannabis convert light from the sun into energy and release oxygen (respirate). When the lights go out, even though the plant isn't photosynthesizing it continues to respire and that solar energy that has been stored in the cells is then converted to carbohydrates that fuel the plant's rapid growth. So, you can see that an extended light cycle during the vegetative stage would force your plant to store loads of solar energy to fuel rapid growth during the dark cycle.

Cannabis plants are also photoperiod, meaning that their cellular structure is naturally sensitive to the changes in hours of daylight it sees. It cannot transition from its growth stage (vegetative) to flowering until it experiences at least 12 or more hours of darkness per day – this is considered the biological trigger to induce blooming. When gardeners take advantage of the great outdoors, they can expect their plants to slip into flowering late in summer as the days grow shorter and nights grow longer.

What's the Best Light to Grow Cannabis?

Lighting. The jury is still out. Everyone has their favourite bulb but what works for one person might not work for another. To further that, what works for one strain might not be right for another, either. It's trial and error, but essentially, cannabis plants love lots of bright, full-spectrum light, which can be delivered by:

• LED (Light Emitting Diode)
• HID (High-Intensity)
• CFL (Compact Fluorescent Lamps)

LEDs

First, we'll look at LED lights – these kinds of bulbs are gaining in popularity for household use because they produce the same amount of light as a regular bulb but with less energy expenditure. The bad news? The physical bulbs tend to be on the expensive side, and as a single LED bulb won't provide enough light necessary to help your plant thrive, can be prohibitive when you realise you'll need more than one or two.

HIDs

The next options are High-Intensity Discharge bulbs, affectionately nicknamed HIDs, for short. These bulbs are great for producing a lot of light, but they also produce a lot of heat. Overheating your crop is bad news bears, and you'll also need to invest in a full exhaust system if you choose this route or risk wasting your time and effort.

Just considering the above, it should go without saying that HIDs are the most expensive light choices, but they're old school and may win you over simply for tradition's sake.

HID light bulbs come as:

• Metal Halide (most often used during the vegetative stage)
• High-Pressure Sodium (HPS) (preferred during the flowering stage)
• Light Emitting Ceramic (aka ceramic metal halide)

Heads Up! The individual lights listed above do not, on their own, produce the full light spectrum, and it's often recommended to stock up on several of each in order to provide your growing plants the full range they require to guarantee a plentiful, fat crop.

CFLs

Last, we'll look at Compact Fluorescent Lights, the kind you install in the ceiling. CFLs are popular because they are energy efficient, you don't need a bunch of different styles on hand and you don't need to worry about them overheating your grow room (they don't produce a lot of heat). They are pretty large, however, and they aren't the most efficient for cannabis growth unless you are cultivating strains that tend to be short and fat.

What's the Deal with Photosynthesis?

If you haven't guessed it by now, light is an extremely important factor in growing cannabis, and your plants' near constant need for the right source of light was historically a significant tell to law enforcement monitoring the electrical grid for excess usage — something that has largely changed since cannabis was legalised across Canada under the Cannabis Act.

You may vaguely remember learning about photosynthesis during high school biology; that's information that comes into play here, as it's this process that is key to your success.

By way of a brief refresher: light is made up of different colours in a spectrum. Good old, natural sunlight, being as magnificent and all powerful as it is, is what you'd consider full spectrum light, and the ideal source for your cannabis garden. Because most people aren't capable of growing in the great outdoors (or even planting in a greenhouse), it's important to do some research in advance to guarantee you get the right light intensity for the job:

• Too low an intensity and you risk your plants growing long and leggy since they will have to stretch toward the light to catch those rays.
• Too high an intensity and you risk stunting the growth of your plant, and/or burning the delicate leaves.

Tip: Your light source should always be about two feet away from the crown of your cannabis plant.

Cannabis Stages & Light Changes

One of the more complicated issues with growing good cannabis is the need to change your light schedule in order to transition your plants from one stage to the next. Of course, this can be mitigated by buying auto-flowering marijuana seeds, a strain that adapted to the harsh conditions of its native regions (like Russia) to transition once the plant reaches a certain height as opposed to a change in photoperiod.

In the case of regular feminised marijuana seeds, during the vegetative stage your plants will require up to 18 hours of light, while during the flowering stage the ratio becomes 1:1 – 12 hours light, 12 hours darkness.

The Dark Cycle

Equally important to the health and success of any cannabis crop is the time the plants spend in darkness. As we know, increased periods of darkness is the biological trigger for a cannabis plant to enter its flowering phase.

You may not know that anything short of pitch black in your grow room could stress your plant and disrupt flowering. It can even force a female plant into an intersex plant.

• Check your grow tent or rooms for cracks/tears and repair immediately
• Cover your greenhouse at night to ensure complete darkness for the duration of the dark cycle
• If you need to tend to your indoor grow room at any time during your plant's designated dark cycle, use only green light, as this won't put any stress on your delicate babies.

The Dark Cycle and Vegetative Growth

Did you know that photoperiod cannabis plants can be kept in vegetative growth indefinitely as long as they receive 14 or more hours of light per day?

The light schedule you settle on for your vegging period is up to you – but the debate rages over which is better: 18-6 or 24-0. Anywhere between should do the trick, although you're welcome to experiment and see what works best for you and your garden.

Some breeders have been experimenting with a new 6-2 schedule, with three light/dark cycles occurring during a 24-hour period. The thought process behind this scheduling is the 2 hour periods of darkness give the plant a chance to rest and process CO2 more effectively.

The Dark Cycle and the Flowering Stage

For your plant to start budding, you need to introduce a schedule of 12 hours of light and 12 hours of darkness. This occurs naturally when plants are outdoors, as the days grow shorter.

Master Gardener Tip: to encourage a more successful harvest, leave plants in complete darkness for 36 hours before starting the new 12-12 light schedule – this ensures the increased presence of phytochrome red, which triggers flowering.

Next to nutrition and potting mediums, from germination to harvest, lighting is a critical tool in your belt, and can make or break your cannabis garden. Once you've bought your favourite cannabis seeds from Pacific Seed Bank Canada, we say… Let There Be Light!

The Pacific Seed Bank Germination Guarantee

 Pacific Seed Bank offers one of the most comprehensive Germination Guarantees on the market. Although we're confident that we are offering our valued customers some of the highest quality seeds available, all of which have been tried and tested to give you a germination rate of at least 90% (two-seed minimum*), we understand that sometimes external factors can affect your seeds and influence their viability. As long as you follow the method outlined in our detailed germination guide, your purchase is eligible for our 90% Germination Guarantee*.

*While our ultimate goal is to leave our customers feeling happy and satisfied with their Pacific Seed Bank purchase, we cannot replace single failed seeds. Our Germination Guarantee pertains to two (2) or more non-viable marijuana seeds that still meet the less than 90% germination requirement (i.e. if only 8/10 of your seeds germinate, this equates to an 80% success rate and is eligible for our guarantee, where if 23/25 germinate, this is a 92% success rate and technically not eligible for our guarantee.)  

**Seeds that have been germinated using one of the two alternative methods outlined above will not be eligible for our Germination Guarantee.