The Best Lighting For Growing Indoor Cannabis for Solventless
Cannabis enthusiast and student of the art of solventless extraction
Lighting is one of the most important factors for growing cannabis indoors. Light is the primary source of energy for plants and is essential for photosynthesis, which is the process by which plants convert light energy into chemical energy to fuel growth and development. Adequate and proper lighting is critical for cannabis plants to grow healthy, strong, and produce high-quality buds. What’s more, the right lighting allows those buds to develop the richest and most potent resin possible, which is the holy grail for solventless extractors and hash makers.
The sun provides all the light that outdoor cannabis needs from seed to harvest, but growing indoors is a different story. Indoor growers have choices to make when it comes to lighting. The goal of indoor lighting is to replicate the sun as closely as possible. While there’s no substitute for the full spectrum and intensity of sunlight, different types of artificial lights are able to mimic certain characteristics of natural sunlight.
Variables To Consider When Sourcing Lights for Indoor Grow Rooms
The main factors to select for include the intensity and spectrum of light.
The intensity of light is important for promoting growth and development. The most important metric for measuring light intensity is the lumen, which is the standard measurement of light output. The more lumens a light emits, the brighter the light appears. Each cannabis plant needs exposure to approximately 2,500 to 3,000 lumens of light. However, upwards of 4,500 lumens will optimize for maximum growth. A 4,500-lumen bulb generally covers a 3x3-foot space with adequate lighting for growing cannabis indoors.
However, beware of giving the plants too much of a good thing. Light stress is definitely possible, with an overabundance of intensity leading to heat stress or “bleaching”. Burning, or bleaching, appears as a whitening of the area, typically the tops of flowers, where the plant can’t produce enough chlorophyll to handle the high intensity of the light. If this happens, try to raise the level of the light above the plant, or with LED’s, dim the output a bit.
PPFD meters, or spectrometers, are great tools to measure the intensity of your lights and stay within the optimal range.
The other main variable for selecting the best lights for growing cannabis is the spectrum of light that it emits. Different colors of light promote different types of growth. Blue light promotes vegetative growth, while red light promotes flowering and the development of buds. Therefore, for the vegetative stage, a high-intensity blue light is needed, while red light is needed for the flowering stage.
We’ll look at which types of lights tend to produce blue light, and which lights tend to produce more reds.
First, a quick note about photoperiod, temperature, and overall environment as it relates to indoor lighting.
Cannabis plants are sensitive to the photoperiod (the amount of time the plants are exposed to light in a 24-hour period). During the vegetative stage, plants need 18-24 hours of light per day, while during the flowering stage, they need 12 hours of light per day. Some growers use one type of light during the vegetative stage, and another type of light for the flowering stage.
Cannabis is also sensitive to temperature. Some lights, like HPS bulbs, run hotter than other lights, like the cooler LEDs. Stay diligent to avoid heat stress, which can affect the quality of your resin.
Finally, adequate lighting can also help prevent pests and diseases by providing a healthy growing environment for the plants. Plants that don’t receive enough light aren’t able to maintain vigorous growth over their natural course of development, making them more susceptible to disease and infestation.
Different Types of Lights to Consider for Growing Cannabis Indoors
As previously mentioned, different stages of growth require different spectra of light. For the vegetative stage, a high-intensity blue light is needed, while red light is needed for the flowering stage.
The best lights for growing cannabis indoors have typically been high-intensity discharge (HID) lights, such as metal halide (MH) and high-pressure sodium (HPS) lights. These lights provide a high level of light intensity and spectra that are well-suited for promoting plant growth and development.
That said, LED lights have seen significant improvements in recent years and are now wildly popular among indoor cannabis cultivators. LEDs are energy efficient, emit less heat, and can be adjusted to provide specific spectra for different stages of growth.
Fluorescent lights are generally not suitable for growing cannabis indoors, as they lack the intensity needed to promote vigorous growth. An exception is in cloning plants, where T5 fluorescent bulbs can provide the right amount of light to help young cuttings take root and get a good start in their first couple of weeks of growth.
Metal Halide (MH)
Metal halide (MH) lights are a type of high-intensity discharge (HID) lights that emit a spectrum of light that is rich in blue and white wavelengths, which are ideal for promoting vegetative growth and strong stem and leaf development in cannabis plants.
Blue light promotes vegetative growth and helps the plants develop strong stems and leaves. MH lights are commonly used during the vegetative stage, as they provide a lot of blue light.
MH lights provide a high level of light intensity and are known for their energy efficiency and long lifespan. They also emit more heat than high-pressure sodium (HPS) lights, so it's important to have proper ventilation and cooling in the grow room to avoid any issues with heat stress. That said, cannabis plants can tolerate slightly higher temperatures in the vegetative stage than their flowering stage.
Bear in mind that MH lights also tend to have a high energy consumption.
High-Pressure Sodium (HPS)
High-pressure sodium (HPS) lights are a type of high-intensity discharge (HID) lights that have been the gold standard for flowering plants indoors for decades. They emit a spectrum of light that is rich in red and orange wavelengths, which are ideal for promoting flowering and the development of resin in cannabis plants.
During the flowering growth cycle, cannabis plants need a spectrum of light that is rich in red light. Red light promotes flowering and the development of buds and a thick coating of resin. High-pressure sodium (HPS) lights are commonly used during the flowering stage, as they provide a lot of red light.
HPS lights provide a high level of light intensity and are known for their energy efficiency and long lifespan. They also emit less heat than metal halide (MH) lights, making them better for use in small grow rooms or grow tents where heat buildup can be an issue. However, in compact spaces, LED lights are the way to go, as they produce the least amount of heat of any light.
HPS lights have a high energy consumption and produce heat, so it's important to have proper ventilation and cooling in the grow room to avoid any issues with heat stress.
LED
LED grow lights are composed of multiple Light-Emitting Diodes, which give LED lights their name. These diodes are built into a casing or mounted onto an aluminum board and powered by a driver. Unlike HPS lights, LED lights don't require external ballasts.
While HPS technology relies on pressurized gas to generate a high intensity discharge of light, LED’s rely purely on the electrical diodes to create light.
LEDs are becoming the first choice for many indoor growers. They can be adjustable in both spectrum and intensity, produce minimal heat, are energy-efficient, and are exceptionally long-lasting. Adjustable LEDs give growers the flexibility to produce more blue light during vegetation, then more red light during flowering. Their low heat output also makes LEDs great for tent and closet growing, where compact space is a limitation.
The cost of high-quality LED grow lights has been coming down, making them even more accessible to the home grower. That said, LEDs are generally more pricey than HPS lights at the time of writing.
Read more in our article How To Choose an LED Grow Light.
Conclusion
In summary, lighting is important for growing cannabis indoors because it provides the energy and the specific spectra needed for plants to grow healthy and produce high-quality resin. It’s a good idea to maximize your budget in regards to lighting. Great genetics and optimal lights are two variables that can make or break your entire operation.
Many indoor growers opt for Metal Halide (MH) lights during vegetative growth, and High-Pressure Sodium (HPS) lights for flowering. Fluorescent lights, like T5 bulbs, are only suited for cloning and the first couple weeks of root development.
A high-quality LED can be modified to produce more blue light during vegetation and more red light during flowering, making these lights a versatile option for the indoor grower. Many growers see LED lights as the future of indoor growing.
What’s your ideal light setup for growing indoors? Let us know in the comments!
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FREQUENTLY ASKED QUESTIONS
Why is it important to choose the right lights for growing cannabis indoors?
Light is the primary source of energy for plants and is essential for photosynthesis, which is the process by which plants convert light energy into chemical energy to fuel growth and development. Adequate and proper lighting is critical for cannabis plants to grow healthy, strong, and produce high-quality resin.
What is the best light for cannabis during the vegetative stage of growth?
Metal halide (MH) lights are a type of high-intensity discharge (HID) lights that emit a spectrum of light that is rich in blue and white wavelengths, which are ideal for promoting vegetative growth and strong stem and leaf development in cannabis plants. LEDs adjusted for the blue spectrum are also good for the vegetative stage of growth.
What is the best light for cannabis during the flowering stage of growth?
High-pressure sodium (HPS) lights are a type of high-intensity discharge (HID) lights that have been the gold standard for flowering plants indoors for decades. They emit a spectrum of light that is rich in red and orange wavelengths, which are ideal for promoting flowering and the development of resin in cannabis plants. LEDs adjusted for the red spectrum are also good for the flowering stage of growth.
Can you use fluorescent lights to grow cannabis?
Fluorescent lights are generally not suitable for growing cannabis indoors, as they lack the intensity needed to promote vigorous growth. An exception is in cloning plants, where T5 fluorescent bulbs can provide the right amount of light to help young cuttings take root and get a good start in their first couple of weeks of growth.
Can you grow a cannabis plant next to a window without a light indoors?
Sunlight coming in through a window does not provide the intensity of light needed to grow a healthy, robust cannabis plant all the way through its flowering cycle indoors. It’s okay to use sunlight as a supplement, but a high-quality grow light should be the main source of light.
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