New To Grow Lights

This is a simple and complete guide to the principles of grow lighting. Our grow lighting experts will help you decide the best grow light for you.

The grow light is the source of energy your plants need to grow by a process called photosynthesis. The more light you deliver to your plants the higher the rate of photosynthesis which means more growth and higher yields.

Our grow lighting guide will help you maximise your yield for your experience level and your plant genetics.

What Makes A Good Light?

Plants need a lot of light to grow

The light intensity plants require to grow vigorously is about 200 times more than humans need to see indoors. Grow lights must be powerful enough to deliver high intensity light and efficient enough to do it cheaply and with minimal heat output.

Light spectrum or color of light
Plants require a 'full spectrum' light which has the right amount of each color spectrum to grow healthily. Grow lights must deliver the correct proportions of blue, green and red light the plants need.

Each plant should get the same amount of light
The grow light should spread the light uniformly over all the plants in the grow area. This ensures all the plants reach their potential yield.

Grow lights must be tough
Grow rooms and grow tents are hot and humid environments. Grow lights must run for up to 20 hours per day and last for years. They must be designed and built to last in tough conditions.

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How Much Light Should A Grow Light Deliver?

To grow big plants quickly you need powerful LED grow lights delivering high light intensity. For grow lighting the measurement of light output is PAR (Photosynthetically Active Radiation) and is measured in units called µmols.

Powerful grow lights use a lot of energy so they should also be efficient to keep running costs low.

Grow light efficiency is measured in Photosynthetic Photon Flux output for every watt consumed (also know as PPF/joule).

What Color Or Spectrum Of Light Is Best?

Plants absorb blue, green and red light which combined together make white light. This is called the PAR range, PAR stands for Photosynthetically Active Radiation.

The proportion of each color or wavelength of light can be varied to effect plant characteristics such as height.

Full spectrum grow lights emit white light with the required proportions of each part of the spectrum to produce healthy plants.

It has been shown that light outside of the PAR spectrum such as Ultra Violet and Far Red can also contribute to plant growth and shape. However they are not required to grow big healthy plants.

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The Simple Takeaway

To grow big healthy plants you need high PAR intensity. For Photoperiod plants we recommend average PAR of 900 µmol/m²/sec. Expert growers can utilise up to 1,400 µmol/m²/s PAR intensity with high performance environment controls, genetics and nutrients to suit.

Auto flowering plants have a longer 20 hour light cycle and a PAR intensity of about 600 µmol/m²/s is as much as they can absorb.

All grow lights emitting white light are 'full spectrum' grow lights and will grow healthy plants.

The light should be delivered evenly over the grow area. You can see the uniformity with a PAR map showing the PAR intensity across the specified grow area.

Grow lights should be rated for wet and hot environments.

Grow Light FAQ

1. What are grow lights, and why do I need them?

Grow lights replicate sunlight, giving plants the specific light spectrum and intensity they need to grow indoors. If your space lacks natural light or you want to grow year-round, grow lights are essential for healthy plants.

2. What types of grow lights are available?

There are three main types of grow lights:

LED Lights (The Best): Energy-efficient, long-lasting, and full-spectrum (ideal for most plants).
Fluorescent Lights: Were used in the past for young plants but are now phasing out due to poor efficiency and environmental hazard.
HID Lights: High-intensity Discharge lights such as Hight Pressure Sodium (HPS). Cheap to buy but less than half the efficiency of LED lights

2. What does PAR mean?

Photosynthetically Active Radiation (PAR) is the portion of the electromagnetic spectrum used by plants in photosynthesis.

The range of light wavelengths plants absorb is the same as the visible spectrum between 400nm (blue) to 700nm (green).

2. What does PPF and PPFD mean?

PPF or Photosynthetic Photon Flux is a measure of the total number of photons (individual particles of light) within the PAR range emitted by a grow light, typically expressed as micromoles per second (μmol/s).

PPFD or Photosynthetic Photon Flux Density measures the number of PAR photons that reach a specific surface area (usually expressed in square meters) per unit of time. PPFD is measured in micromoles per square meter per second (μmol/m²/s) and provides a more practical measure for assessing the light available to plants at a specific point.

2. What is a µmol?

The mole (symbol mol) is a unit of measurement of particles. One mole contains exactly 6.02214076×1023 particles. The "µ" symbol represents "micro," meaning one-millionth, so 1 µmol is one-millionth of a mole.

In grow lighting a µmol (micromoles) is the amount of photons (light particles) plants receive in a given period with units µmol/m²/s

3. Which grow light is best for beginners?

LED grow lights are the best choice for beginners. They’re energy-efficient, easy to set up, and offer a full spectrum of light to support plant growth at all stages.

4. How far should my grow light be from my plants?

The distance depends on the type of light and your plants’ needs:

LED Lights: Typically 12–24 inches above the plant canopy.
Fluorescent Lights: 6–12 inches above.
HID Lights: 24–36 inches above.
Always follow the manufacturer’s recommendations and adjust based on plant response.

5. How many hours of light do my plants need?

It depends on the type of plant:

Seedlings and vegetative: 16 hours per day.
Flowering and fruiting plants: 12 hours per day.
Auto flowering plants: 20 hours per day.
Use a timer to ensure consistency.

6. What’s the difference between red and blue light?

Blue light: Encourages leafy growth and strong stems.

Red light: Promotes flowering and fruiting.
Full-spectrum grow lights combine both to support plants at all stages.

7. Can I leave grow lights on 24/7?

No. Plants need a dark period for rest and essential processes like respiration. Stick to the a light schedule for your specific plants.

8. How do I know if my grow lights are working?

Signs your plants are happy:

Upright, vibrant growth.
No stretching or leggy stems (a sign of insufficient light).
Healthy, consistent leaf coloration.

About Migro

Why I Set Out To Make The Best Grow Light

Fed up with the deceit and bad claims in the grow light space in 2016. I set out to make the best light I could. Using my youtube channel and word of mouth to prove out the value of what we have made and where we have come from as the Migro Community.