Lighting Needs of Cannabis Plants

As any cannabis cultivator will tell you, one of the most critical aspects of the indoor environment is light. Light plays a role in every metabolic process related to plant growth, from nutrient uptake to transpiration. Without proper lighting, cannabis plants don't stand a chance.

What lighting characteristics have the biggest impact for the indoor cannabis cultivator? Throughout the grow, you'll need to consider:

  • Photoperiod (lighting schedule)
  • Light intensity
  • Light spectrum

Photoperiod (Lighting Schedule)

Throughout the plant's growth cycle, you'll need to adjust the lighting schedule, which is the division of night and day the plant receives within 24 hours. This is because plants interpret changing photoperiods, which naturally occur thanks to changing seasons. 

Chemical signals alter the growth patterns in response to day-length transitions from spring to summer to fall. Indoor growers use light to replicate and manipulate plant growth. As you adjust the indoor photoperiod, you signal to the plant that it is time to enter the next growth stage.

Lighting-Needs-for-Growing-Cannabis-IndoorsLight Intensity (PPFD and PPF)

Grow light intensity significantly impacts cannabis plants' growth and yield. Light intensity is measured through photosynthetic photon flux density (PPFD). This measurement refers to the number of photosynthetic photons that fall upon a square meter of surface (like a plant leaf) in a given period of time. PPFD is measured in micromoles of light per square meter per second (µmol/m2/s).

Photosynthetic photon flux (PPF) is the number of photons emitted from a lighting device. Specifically, these are the photons of light that a plant can absorb and utilize for photosynthesis, the process by which plants drive their growth. 

In the grow light industry, PPF is sometimes incorrectly used interchangeably with PPFD. PPF is the unit available on a light manufacturer's data sheet to represent the photons emitted by a fixture. However, it is not an accurate measurement of the number of photons that reach the canopy. 

Light Spectrum

Another factor for indoor grow lights is the light spectrum. Depending on where the plant is in its growth cycle, you'll need to target a specific light spectrum for that stage—for example, cloning, vegetative, or flowering. Indoor growers need to understand the spectral needs of their plants to trigger proper development.

Lighting Considerations for Seedlings and Cuttings

Most of what a seedling initially needs is packed into the seed itself. But, once the seed produces cotyledons and begins taking in light, its metabolic processes kick into action. Rapid growth can begin once the seedling has started absorbing light photons through its leaves. 

Photoperiod for Seedlings and Cuttings

Because the goal is to get seedlings and cuttings rooted as quickly as possible, many growers offer their young plants 18 to 24 hours of light in the beginning. 

By not offering a period of darkness, seedlings work around the clock to establish a dominant taproot, develop fine root hairs, and eventually begin displaying leaves. 

Once cotyledons and true leaves have begun to show, growers start altering the indoor photoperiod to encourage vegetative growth.

Light Intensity for Seedlings and Cuttings

Seedlings and cuttings prefer mild light intensity, with relatively low but steady PPFD — between 100 to 180 µmol/m2/s. 

Because of their young and fragile state, young cannabis plants are sensitive to excessive or deficient lighting intensity. 

Dialing in light intensity with young plants is critical. However, it can vary based on fixture type and facility design. 

Light Spectrum for Seedlings and Cuttings

Due to the earth's axial tilt, the atmosphere tends to deflect many of the sun's more intense red and far-red rays during the spring, allowing for the penetration of more blue light. This means cannabis plants expect cool, blue light in the early phases of development.

In attempts to replicate this lighting indoors, growers have long used lighting with higher blue spectrum content for seedlings and cuttings, as well as for vegetative growth. 

Lighting Considerations for Vegetative Growth

Once a seedling has matured and begun producing multiple sets of true leaves, the plant can be said to be in vegetative growth. At this phase, the plant focuses on creating strong stems and lots of foliage to convert light energy into growth. 

Photoperiod for Vegetative Growth

To replicate the long summer days, cultivators typically set their lighting schedule to 18 hours on and six hours off during vegetative growth. A photoperiod of 18/6 strives to replicate nature by preventing the plants from entering into a flowering cycle. As flowering is triggered in nature when the sun photoperiod reaches a 12 hour on/off photoperiod, the 18 hours is designed to accelerate vegetative growth as well as prevent the plant from flowering.

Light Intensity for Vegetative Growth

During vegetation, plants attempt to produce as much foliage as possible to make the most out of the late summer light they will receive when they flower. The more foliage produced during the vegetative cycle, the better energy production they can direct into larger, more prolific flowers.

Cultivators typically aim between 400-800 µmol/m2/s PPFD during vegetative growth.

Light Spectrum for Vegetative Growth

Like seedlings and clones, cannabis cultivators aim to keep a significant amount of blue light in the spectrum during vegetative growth. As vegetative conditions mimic spring/early growing conditions, ample blue light is essential.

Combined with the 18/6 photoperiod, cannabis plants interpret this higher blue content light as a sign that they have time to prepare for flowering. Plants only enter flower when the photoperiod changes and the light spectrum shifts toward the red end.

Lighting Considerations for Flower

The final stage of the process, flowering, is where all the magic happens. The plant's hard work of fortifying during vegetative growth pays off as buds begin developing all over the plant. 

Photoperiod for Flower

One of the more dramatic changes for indoor cultivation flowering is the shortening of the photoperiod from 18 hours on, six hours off to 12 hours on, 12 hours off, to mimic the summer photoperiod

The shortening of the day from 18 hours to 12 hours indicates to the plants that it is time to begin developing flowers and producing a resinous coating. Depending on production schedules and cultivar, flowering can take eight to 10 weeks.

Light Intensity for Flower

Flowering cannabis plants use significantly more light than in other growth phases. Studies have shown that increased light intensity is directly linked to increased harvest size and higher concentrations of cannabinoids. 

Most cultivators suggest increasing light intensity to 800 to 1500 µmol/m2/s PPFD during flower. Given ample space, airflow, and temperature mitigation, LED grow lights can run at full intensity during flowering. Plants will happily absorb nearly all available light, assuming the lights are not too close to the canopy, there is ample CO2 and nutrients, and the environmental conditions support healthy growth. 

Light Spectrum for Flower

As summer transitions, much of the sun's blue light is reflected away by the atmosphere, allowing for penetration of more red and far-red light. Plants interpret this spectrum and the 12-hour days as a signal to flower. 

Cultivators replicate this transition in the grow room by introducing more red and far-red light into the spectrum. Before LED grow lights, this was typically achieved by swapping metal halide bulbs for high-pressure sodium bulbs, known for emitting more red light rather than bluer light. 

Since LED grow lights have entered the commercial cannabis industry, growers have more options for introducing red spectrum, including lights with full plant spectrums, like TSRgrow's Advanced LED Lighting Solutions.

TSRgrow LED Grow Lights: Offering Unparalleled Control

At TSRgrow, we've developed solutions for every horticultural lighting need. We're the industry leaders in LED grow lights for cannabis cultivation, elevating the "standard" LED grow light far beyond the conventional.

Installation and Maintenance

Our LED grow light solutions have eliminated all local ballasts/drivers from the fixture, meaning that the system produces virtually no extra heat inside your grow room. This means increased energy savings, reduced HVACD equipment and operational costs in the grow room, as well as the ability to maximize PPFD by crop steering through lighting control with unlimited zone control

Onboard/local ballasts/drivers have been replaced with remotely located power servers, centralizing maintenance outside the grow room. In addition, our ballast-free grow lights feature plug-and-play technology, making installation and mounting as simple as possible. 

Centralized Control Over All Parameters

TSRgrow's LED grow lights are designed to integrate into our TOTALgrow Solution. Incorporating our proprietary GROWHub monitoring software, our TOTALgrow Solution offers unparalleled control and customization over the entire lighting system. 

GROWHub utilizes remotely located sensors throughout the facility to monitor and maintain optimal growing conditions. In addition, GROWHub tracks analytics from cycle-to-cycle to determine which settings delivered maximum growth potential for plants. With historical data, growers can easily replicate these conditions time and again for maximum yields. 

GROWHub's active monitoring provides a seamless transition between growth phases, incorporating changing photoperiods into its scheduling. GROWHub and TSRgrow's LED grow lights take all the guesswork out of grow room lighting. 

Easy Dimming and Intensity Controls

TSRgrow's LED grow lights also offer unparalleled control over light intensity and dimming. Thanks to GROWHub's remote smartphone and computer interface, all of these settings can be changed with the swipe of a finger. 

Our grow lights' plug 'n play technology also offer cultivators an enhanced ability to control their grow room without any dimming wiring and mounting hardware. Dimming is built into the software. Utilizing our industry-leading LED lights, partnered with GROWHub, means no more dimming wires, contacts, or relays, freeing growers to focus on their crop rather than their equipment. 

Full Spectrum for all Phases of Growth

Of the many features of our grow lights, one of the most appealing is the full plant spectrum. We've included diodes in our grow lights that offer every aspect of the full light spectrum suitable for plants, including green, yellow, red, far-red, and even ultraviolet light. 

With the help of GROWHub, growers offer their plants a complete spectrum through every stage of growth without ever having to change a bulb or a fixture. 

TSRgrow: Offering Solutions for LED Grow Lights

Our years of research and development have led us to the forefront of the LED grow light industry. Our LED grow lights offer unparalleled quality and control, and that's only the start. Paired with our GROWHub software, our lights provide growers with a TOTALgrow Solution for all of their lighting needs. 

Whether you're a new business in the initial stages of design or looking to retrofit or transition to LED grow lights, TSRgrow can help with your design and buildout. Contact us today to see what TSRgrow can do for you!


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