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Best Artificial Light Source for the Vegetative Stage of Marijuana Growth

The vegetative stage of growth for marijuana is the stage that builds a strong or weak foundation for the upcoming flowering stage. During the vegetative stage, marijuana plants build structural integrity. The structural integrity of a plant plays a key role in determining not only the amount of flower sites, but also the overall yield. Healthy vegetative plants are essential for a successful perpetual marijuana garden. Unfortunately, many marijuana growers don’t understand just how important the vegetative stage is. Many gardeners focus too heavily on the flowering stage of growth. After all, the flowering stage is where the real magic happens. That being said, unhealthy plants that are cycled into the garden’s flowering stage will never produce up to their full potential.

Even if the flowering stage is implemented flawlessly, unhealthy plants will not produce as well as healthy plants. On the other hand, growers who pay attention to all of the stages of growth will have better results and a higher return on investment. One of the most important factors that contributes to the health and vitality of cannabis plants during the vegetative stage is the light source. For indoor horticulturists, the light source is the driving force behind all plant growth. Choosing the proper lighting system for each stage of growth can go a long way in maximizing a garden’s performance. Although there are many different artificial light sources that will work in the vegetative stage, choosing the right system for your particular application will help produce healthy vegetative plants. Taking a quick look at some of the most popular and efficient lighting systems used for vegetative growth will give cannabis growers some insight into which lighting system will best suit their needs.

HID Grow Light
High Intensity Discharge (HID)

High intensity discharge (HID) lighting includes metal halide and high pressure sodium lights. HID lighting has been the industry standard for many years due to its ability to produce intense light and light that is usable by plants. Other lighting technologies offer higher efficiency in terms of usable light (photosynthetically active radiation or PAR), but HID lighting offers higher intensity which can be very beneficial for indoor marijuana crops. In recent years, many marijuana growers have turned away from HIDs in the vegetative stage and have upgraded to more efficient lighting technologies.

However, in some garden set ups, HIDs are still the better choice for vegetative growth. An example would be a gardener who wants to grow monster plants. Due to legal limitations placed on marijuana plant numbers, a grower may want to grow the largest plants possible. In order to grow these monster plants, a very intense light source is required. HID lighting systems may be the better choice for this type of garden. Another example of HID lighting being the better choice for vegetative growth is a garden where the vegetative and flowering stages are done in the same room. For this type of garden, it is far more convenient to utilize the same lighting system for both stages and that lighting system is usually a HID system.

Perhaps the biggest disadvantage of vegetative growth under HID lighting is the uneven distribution of light. Although lighting reflectors help distribute the light more evenly, a HID system will emit the most intense light directly under the bulb. This is why there is more accelerated plant growth directly beneath the bulb than on the outskirts of the light footprint. In order to combat this, a grower should rotate the position of his or her plants to even out the growth of all the plants. In terms of vegetative growth, the more uniform and consistent the growth, the better. Transitioning a uniform plant canopy into the flowering stage is not only easier to manage, but also automatically uses the light energy more efficiently. Any time indoor horticulturists can make more efficient use of their given light energy, they will be rewarded in higher returns on their investments.

T-5 Fluorescent Grow Light

Some old school growers may remember when shop lights (T-12 fluorescents) where common place in a vegetative marijuana garden. Although T-12 systems can work to grow plants, they are quite inefficient compared with newer florescent technologies. T-8 fluorescents are a step up from the old T-12s and can be used for vegetative growth. However, the T-5 florescent technology is the pick of the litter. T-5 fluorescents are super-efficient and, therefore, have made a name for themselves among marijuana growers. The attributes that make the T-5 system so appealing include a lower operating temperature, an even distribution of light and a relatively long life span. There is also a certain level of customizability as there are bulbs available in various spectral outputs. Many growers prize the T-5 fluorescent’s even light distribution for the vegetative stage of growth. In fact, the light energy emitted from a T-5 system is completely uniform the entire length and width of the fixture. The uniformity of light distribution equates to more even vegetative growth and a better foundation for the flowering stage.

Induction Fluorescents

My personal favorite lighting system for marijuana’s vegetative stage of growth is an induction fluorescent system. This is mainly due to their incredible longevity of light energy output. Much like regular fluorescents, induction fluorescents offer a balanced spectral output at a lower heat signature than HID lighting. However, induction fluorescents differ greatly from other fluorescents in a few ways. First, induction fluorescent lighting requires no electrodes. If you have ever noticed the area closest to the electrodes turning dark brown or black on a standard fluorescent bulb, you have witnessed the visual effects of the light energy degrading. In other words, the electrodes cause a loss of the internal components, which, in turn, causes the bulb to lose some of its effectiveness. This is why, for horticultural purposes, fluorescent bulbs must be replaced every year or so.

Induction fluorescents, on the other hand, will retain their light energy output for upwards of ten years. In fact, cannabis growers can bank on using their induction fluorescent systems continuously for 5-7 years before having any reduction in PAR. This is the main reason I prefer induction fluorescents for my vegetative growth. Growers who use induction fluorescents can rest assured that their plants are receiving the same light energy garden cycle after garden cycle. Much like T-5 fluorescents, induction fluorescents also offer the same advantage of even light distribution. When it comes to efficiency and longevity for the vegetative stage, it is hard to compete with induction fluorescents.

Light Emitting Diodes (LEDs)

LED fixtures were slated to be the future of horticultural lighting when they first appeared on the market. Unfortunately, many of the initial LED fixtures failed to meet the demanding needs of indoor horticulturists. Luckily for marijuana growers, LED manufacturers didn’t give up and the horticultural LED market is now has a competitive mixture of some great and some not so great horticultural LED lighting systems. The biggest advantage of horticultural LEDs is their ability to be customized. Horticultural LED lighting systems can be customized to emit particular wavelengths of light. In other words, LEDs gives the manufacturer the opportunity to create a lighting system that will have a higher PAR output.

LED Grow Lights

The customizability of LEDs can also mean a better lighting system for particular stages of growth. During the vegetative stage, plants tend to make better utilization of blue light energy. LED systems that are specifically designed for vegetative growth generally have a higher amount of blue light compared with other colors. Aside from customizability, LEDs offer a couple of other advantages. Like fluorescents, they operate at a much cooler temperature than HID lighting systems. This reduces the need for cooling and increases overall efficiency. Horticultural LEDs also offer the advantage of longevity. Much like induction florescent systems, horticultural LEDs can be used 5-7 years before seeing a reduction in PAR. Most horticultural LED systems are designed to be used for ten years or more.

How Much Light Energy?

During the initial part of the vegetative stage plants should be slowly acclimated to the intense light. In other words, when transitioning from the clone/seedling stage of growth, the intensity of the vegetative lighting system might cause shock or create stress. Perhaps the best way to stop this from happening is to start with the lighting system raised at least 3-4 feet above the plant canopy and then slowly moving the light down 3-6 inches each day. Over the course of 3-7 days, the plants can be acclimated to the more intense light source. Vegetative plants should be provided with around 40 watts per square foot of garden space. This will be the most efficient for accelerated growth and also prepare the cannabis plants for the flowering stage where they should receive around 50-60 watts per square foot.

Finding the right tool for the job goes a long way in any project. Growing marijuana is no exception. Simply put, if a gardener has the right tools for growing, the garden will be more efficient and productive. Not all gardens are exactly the same, which is why it is so important for growers to understand the different options for lighting systems and how each may or may not work for their given set up. Choosing the most effective and efficient option for the vegetative light is an important step in maximizing a garden’s performance.

For some marijuana growers, high intensity discharge lighting may be the only way to get enough intensity to support tall, robust plants. For other gardeners, finding the most efficient way to grow bushy, uniform plants is the key to unlocking additional profits. Regardless of which lighting system is used, growers who pay as much attention to the vegetative stage as the flowering stage will increase their likelihood of success. That being said, finding the most effective and efficient lighting system for vegetative growth will build a strong foundation for a healthier flowering stage and a more productive harvest.

Eric Hopper is a contributing editor.

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