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What Type of Lighting Do Plants Need?
The first rule of indoor plant cultivation is that not all lighting is created equal. This means that, in the world of plants, they do prefer a specific range of light.
This range is known as photosynthetic active radiation (PAR) and describes wavelengths of light between 400-700 nanometers. For humans, the majority of light looks the same; however, plants experience PAR lighting in a very different way.
When exposed to usable light, such as the light in between 400-700nm, plants undergo photosynthesis, phototropism, and photoperiodism. These three functions are the reason why plants can grow leaves, turn towards the light, and eventually flower.
Therefore, when choosing the right grow light for your indoor grow - you’ll need to find a grow light with an optimized PAR range that caters to your plant’s needs. Let’s take a look at the two dominant color spectrums of light that are commonly used for growing plants indoors.
The White and Blue Spectrum of Light
As the spring comes to a close and summer begins, the sun reaches its apex in the sky. Not only are summer days long, but the light produced by the sun is also incredibly bright. When measured, this light falls under the white and blue spectrum of the PAR range.
Research shows that the bright light associated with the 400-470nm range (bluish-white) promotes strong vegetative growth and increased rooting. It’s for this reason that many indoor cultivators choose to use grow lights that produce light within the 400-470nm range while vegetating their indoor crop.
The Red and Orange Spectrum of Light
As the summer months wane and autumn sets in, the sun no longer reaches its apex in the sky. Instead, the sun begins to skirt across the horizon as the days become shorter - and colder.
The light that’s associated with the angle of the sun during this transition to shorter days is 620-700nm (orange-red). Research indicates that the red-orange color spectrum is a prime influencer for plants to begin the flowering process.
In regards to indoor plants, cultivators use this natural mechanism to their advantage. By harnessing photoperiodism, indoor growers use grow lights that produce light in the 620-700nm range to promote robust flowering.
An Introduction to Common Indoor Grow Lights
When it comes to indoor grow lights - there are three types that are commonly used: high-intensity discharge (HID) lamps, LEDs, and fluorescent lamps (FL and CFL). Let’s take a look at each and their associated technologies.
HID Lamps
High-intensity discharge lamps used to be the most popular lighting appliances for indoor cultivators. The primary reason behind the popularity of HID lamps is their sheer output of light.
HID lamps typically come in various wattage formats, such as 150 watt, 400 watt, 600 watt, and 1,000 watt. The higher the wattage - the stronger and more intense the light. Furthermore, HID lamps are available in the blue-white range (metal halide) and the red-orange range (high-pressure sodium). This means that indoor growers can fine-tune their indoor garden according to the plant’s stage of growth.
HID lamps require a heavy ballast, which is the source of the power that’s sent to the bulb. As the power reaches the bulb, the arc tube and electrodes produce a sustained current of electricity.
However, HID lamps are power-intensive, which means they consume a large quantity of electricity and produce an abundance of heat. Although HID grow light systems are affordable - they are by far the most expensive because they require a significant amount of electricity to power them and to cool down.
LED Lighting
LED lighting is another popular product to use for indoor plant cultivation. LED grow light systems are composed of a multitude of diodes, which are powered by an internal ballast.
Not only are LEDs capable of emitting an abundance of light - they are typically composed of diodes that emit a specific color range. It’s because of this that many LED lights are considered full-spectrum. This means that a single LED light can emit red, blue, white, and orange light that’s optimized for plant growth.
Fluorescent FL and CFL Lighting
Fluorescent (FL) and Compact-fluorescent (CFL) bulbs are high-efficiency lights that are meant to save on energy costs. Although indoor growers can find FL and CFL lighting in appropriate color spectrums and wattages - they are limited in their use.
However, CFL lighting can be optimized for indoor cultivators that are working with a small amount of space - such as a closet or cabinet. Furthermore, CFLs can be used efficiently as supplemental lighting in addition to their primary lighting. FL tubes are also commonly used to provide light to seedlings and smaller plants in the earlier growth stages.
A Comparison Between Popular Indoor Grow Lights
Choosing the best grow light for your indoor grow is never easy. However, take a look at this chart to see the differences between various characteristics of each type of indoor grow light.
| Light | Cost | Efficiency | Lifespan |
|---|---|---|---|
| HID | Medium | Low | Medium |
| LED | High | High | High |
| FL/CFL | Low | Medium | Low |
How To Choose One Light Over The Rest
When it’s time to make a decision on which indoor grow light is best for you - it’s time to look at various factors that are specific to your indoor grow setup:
The plants you grow: You need another grow light if you want to propagate vegetable seedlings to put them in your outdoor garden than for growing a cannabis plant from seed to harvest. Our recommendations below are tailored for growing cannabis, but the same principles apply for other light intensive crops such as tomatoes, peppers, corn, or many other vegetables.
The size of your grow space or tent: You’ll get the best results when your grow space is covered with light at an even intensity. Grow lights come at different shapes, sizes and intensities with the goal to provide an even PAR footprint in the desired intensity effectively.
If you have a large number of plants and an abundance of space, then multiple LEDs or HID bulbs will suffice.
If you have a small area, then a single LED or HID bulb will be adequate. The overall objective with indoor growing is coverage, which means that it’s essential that the indoor grow light that you choose covers the plant canopy entirely.
The budget you have – both to invest and to operate: It is always important to operate your grow economically. But don’t be fooled: Some lights might be cheap to buy but very expensive to operate! Thus, it’s important to define your budget for purchasing the light as well as having a rough idea about operating it.
Also consider heat emission. LED grow light systems are by far the most efficient grow light systems because they do not emit an abundance of heat. Alternatively, HID bulbs produce a significant amount of heat, which will force you to use more electricity from an AC unit to cool the room down.
Even with just these factors, the possibilities for suitable or unsuitable grow lights become vast. There are other considerable factors such as durability, longevity, customer support, the company that’s behind and many more. We have high standards and only recommend grow lights that provide a very good balance of all of them.
Recommended Grow Lights
The technology of grow lights – especially LED – has evolved rapidly through the last few years and using a full spectrum LED grow light is the best option in almost any case. LED grow lights are efficient, tuned for plants, have a long lifespan, are relatively cost-effective to acquire and especially to operate. Therefore, all of our following recommendations cover full spectrum LED plant grow lights suitable for growing from seed to harvest. As not every grow light is the optimal fit for everyone, we’ve created the following two categories that are distinguished by budget and plant count.
Bedroom Grow on a Budget
If you want to grow cannabis from seed to harvest in a small and simple setup with good yields, a light capable of providing a usable PPFD of around 700 µmol/m²/s is desired. This light intensity is sufficient to achieve a DLI level of 45 mol/m²/d for the vegetative phase as well as a DLI level of 30 mol/m²/d for the flowering phase. To optimally use any grow light for cannabis, we recommend our article on DLI levels across the full cannabis growth cycle.
If your grow space is a bit smaller (i.e. a 2x2 ft or 0.6x0.6 m tent), a single LED quantum board will light your plants sufficiently.
Less than $100: ViparSpectra P1000
As a new spin on the quantum board design, the ViparSpectra P1000 provides great value for money and packs a bunch of new features along.
The grow light is ideal for small 2x2 tents and draws only 100 W of power. It is using a mixture of high efficiency LEDs and achieves a good efficacy of 2.26 μmol/J in a noiseless passive-cooled design. The power supply is dimmable that allows you to run your grow at maximum efficiency throughout the growth cycle.
We recommend this grow light to anyone that is seeking the best bang for buck.
If you're running a medium-sized home grow (i.e. a 3x3 ft or 1x1 m tent), a larger grow light or a combination of multiple quantum boards will do the job. We especially like grow lights that provide an even coverage.
Less than $250: ViparSpectra XS3000 Pro
The XS3000 Pro places an optical lens above each LED, which directs the light onto your plants with minimal loss and spreads it evenly across the whole grow space.
The grow light is ideal for 3x3 tents (4x3 ft in the vegetative and 4x2 ft in the flowering phase) and draws 300 W of power. Its full spectrum of 3000K and 5000K white LEDs, 660 nm red and 730 nm far-red LEDs supports your plants from seed to harvest, and the dimmer lets you adjust the intensity to each growth phase.
We recommend this grow light to anyone that wants an even light distribution in a medium-sized grow space.
If your grow is already a bit bigger and you're running on a higher plant count with ambitious yields, our next category might suit you better:
Enthusiast Home Grow
To grow cannabis with maximum yields, CO2 supplementation and carefully adjusting DLI levels across the full cannabis growth cycle is highly recommended. A grow light providing a PPFD of around 1000 µmol/m²/s is desired to achieve a DLI level of over 60 mol/m²/d for the vegetative phase as well as a DLI level of 45 mol/m²/d for the flowering phase.
For a larger home grow such as a 4x4 tent, a large quantum board provides an even coverage at an attractive price.
Less than $300: ViparSpectra P4000
The P4000 is the big sibling of the P1000: a large quantum board with a dimmer knob in a noiseless passive-cooled design.
The grow light covers a 4x4 grow space (5x4 ft in the vegetative and 5x3 ft in the flowering phase) and draws 450 W of power. Its full spectrum consists of 3000K and 5000K white LEDs supplemented with 660 nm red and 730 nm far-red LEDs. According to ViparSpectra, the P series achieves an efficacy of 2.7 μmol/J.
We recommend this grow light to anyone on an ambitious growing journey with a higher plant count.
Grow Light Metrics
When comparing grow lights, don't rely on the wattage alone. More meaningful are the light output (PPF in µmol/s), the efficacy (PPE in µmol/J) and the coverage shown in a PAR map. Our glossary explains these and all other grow light metrics:
Measuring Your Grow Light
As you know by now, even the best selected grow light isn't magically running properly. To optimally set up, adjust, and check your grow light, you'll need to measure the PPFD your plants actually receive.
Once you’ve decided which indoor grow light system is best for your indoor garden, it’s time to monitor your light with a portable light meter. Our light meter app turns your phone into a robust light meter that will reduce your electricity costs, maximize plant health, and increase your overall yield.
When it comes to indoor gardening, efficiency is key – and the Photone app helps your plants reach their potential.
