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Comparing marijuana grow lights: discover which is best for you

Buying marijuana grow lights for your indoor garden can seem like a daunting task because of the many options available and the considerable budget range. Don’t fret.

We’ll go through the different types of grow lights, why they’re important, and their advantages and disadvantages. Then we’ll give you some insights into what might be best for you. Let’s roll.

Why are marijuana grow lights important? 

Cannabis plants generate chlorophyll, a compound that converts light into chemical energy used for growth. We refer to this transformation of elements as photosynthesis.

The best light for growing plants indoors replicates sunlight by emitting light in the suitable spectral range.

Understanding the marijuana light cycle

Photoperiod marijuana plants flower annually according to the seasons if grown outdoors.  This factor limits cultivators to when they can develop such strains.

Cultivars require marijuana grow lights that mimic natural light conditions. Shorten the illumination duration to 12 hours or less for photoperiod cannabis plants to switch from veg to flower until harvest. Check out our light cycle for weed guide for more on this.

Factors to consider before buying a grow light

The world of marijuana grow lights is quite expansive, and it can be confusing and expensive if you purchase something that doesn’t work. You can underbuy or waste money on what you don’t need. Here’s what you need to look out for when making your decision.

How much does a grow light cost?

Cannabis grow lights have varying efficiency and efficacy. Some prefer to start with CFLs or HIDs because they are affordable. It’s better to buy these two first unless you can afford quality LEDs and plan to cultivate long-term.

Many “cheap” LEDs (usually going for less than $100) have low-quality components and do not produce the correct light spectrum.

The initial setup cost for LED grow light for cannabis can be a lot higher than, say, HPS, but this is amortized over the years. Here’s our LED vs HPS comparison to decide which is best for you.

How many grow lights do I need to grow weed?

Power equals poundage, but the wattage metric doesn’t necessarily mean a larger yield. Marijuana grow lights placement makes a big difference. Two 450W HID bulbs set side by side in a meter square grow tent is better than one 1,000W HID bulb.

A typical calculation in the cannabis industry is to expect around 1 gram of dried buds per watt per 20 days. This calculation varies wildly depending on the strain and other aspects of the growing area, such as space and temperature.

Keep it simple in terms of watts and heat radiated by your cannabis grow lights when calculating what you’ll need.

At what cannabis stage do I intend to use the light?

You’ll need different marijuana grow lights for each stage. Some growers use HIDs or MH bulbs for vegging and HPS bulbs for flowering.

Some high-end LEDs allow you to change the light spectrum to suit either vegging and the latter flowering stage of the cannabis plant.

Types of marijuana grow lights

CFL—Fluorescent lights

Fluorescent lights
Fluorescent lights

Fluorescent lights and CFL (Compact Fluorescent Lights) are one of the best grow lights for seedlings. They are; cheap, radiate a full spectrum of colors ideal for veg, and don’t run hot compared to more common HID lighting systems.

You can also change the bulbs for a different color temperature on some CFL options. For example, use more blue light to expedite vegetative growth.

Unfortunately, most CFLs don’t have impressive lumens or PAR output. For this reason, they are ineffective grow lights for weed that’s flowering, resulting in lightweight yields and loose buds.

HID—High-intensity discharge lights

High-intensity discharge lights
High-intensity discharge lights

These illumination systems are the most popular source of artificial light in the market. Why? They are powerful, generating enough glare to penetrate the higher canopy and lower branches of marijuana plants.

HIDs are renowned for producing big yields when used as marijuana grow lights. They usually have reflectors to distribute light through the growing area evenly. MH, and HPS are actually two subdivisions of HIDs

HIDs are pretty affordable nowadays and efficient in converting energy into usable light for your plants. They also have a high CRI (Color rendering index), meaning their glow looks natural. As a result, you’ll find it easier to spot any diseases or pest issues.

On the other hand, HIDs utilized as indoor grow lights for cannabis in a confined room do put out quite a lot of heat, so there’s usually a need for ventilation.

Recommended distances for HID grow lights are usually:

  • 5” to 11” for 150W lights
  • 6” to 13” for 250W lights
  • 8” to 19” for 400W lights
  • 9” to 25” for 600W lights
  • 11” to 31” for 1,000W lights

It’s advisable to wear proper eye protection while working in your garden due to the brightness of the light.

MH—Metal Halide Lights

Marijuana grow lights
Metal Halide Lights

Metal Halide (MH) bulbs offer some of the best light spectrum for vegetative growth. They emit lots of blue light, facilitating the plant to grow short and stout. Blue light makes the plant think there’s not much inhibiting its access to light, so it doesn’t need to grow tall.

Trees grow tall in forests because their shadows create shades of red light.

HPS—High-Pressure Sodium Vapor Lights

Marijuana grow lights
High-Pressure Sodium Vapor Lights

HPS lights are ideal grow lights for weed that’s flowering or any other plants that produce fruit. Most prefer this type of light over MH for both the veg and flowering stages because it’s more powerful, resulting in higher yields.

Many cultivators grow with an MH in veg and proceed with HPS in flowering. MH lights put out more bluish light, while HPS offers a reddish glow. HPS lamps are superb marijuana grow lights for autoflowering strains because of their dual spectrum.

LED—Light Emitting Diodes

Marijuana grow lights
LED grow light

LEDs are the best indoor grow lights for the modern marijuana cultivator. These lighting systems use significantly less electricity than most other options.

In addition, they generate less heat than other lighting systems, making them ideal for use in smaller growing areas or be situated close to the plants. 

The only downsides to LED grow light for cannabis is their high initial cost and risk of buying lackluster products. Quality LEDs have a much longer lifespan than other indoor grow lights for cannabis.

What are the light spectrum, par, and lumens?

Marijuana grow lights spectrum refers to the electromagnetic wavelengths of light produced by a light source. Plants detect light wavelengths, including our visible light and beyond, to receive UV and Far Red spectrum.

People use lumens to measure the amount of light, but this data’s only visible to the human eye. We can only discern light spectrum wavelengths ranging from 289 to 740 nm.

PAR (photosynthetically active radiation) is a metric used to differentiate LED efficacy primarily. 

The light spectrum range that can cause photosynthesis falls between 400 and 700 nm, and growth potential is measured within this spectrum. The best light for growing plants indoors usually has blue and red light peaking in the PAR range—blue for veg, red for flowering.

Vegging plants prefer light levels ranging from 250 to 400  µmol (micromoles), while flowering marijuana grows well between 800–1000 µmol/ms of photosynthetic light. 

A weed grow lights manufacturer that uses lumens rather than PAR shows they don’t have experience with light biology and light physics. Optimal lights for cannabis are very different from everyday lights.

More light results in more weed

Yes, but you should take care not to light burn weed when employing many hot lamps or find a way to ventilate all the heat out. To get even more light means choosing the correct wavelengths of light at different phases of the cannabis plant’s growing cycle.

Distribution is critical, so cannabis grow lights manufacturers who provide legitimate PAR charts for their products are preferable.

Which is the best option for marijuana grow lights?

An ideal option for cannabis grow lights depends on your budget and unique needs. Consider the size of your grow space and whether you can accommodate your cultivar when harvesting and the surrounding fixtures.

The best indoor grow lights spread over your canopy rather than focus on a central area leading to an uneven ceiling. What’s most important is having the proper PAR values spread out well over your canopy, particularly if using the Sea of Green cultivation method.

FAQ related to marijuana grow lights

We’ve answered some of the most common questions we get about grow lights for marijuana below.

How much light does a weed plant need?

Home cultivators usually choose marijuana grow lights using the 400–600W per m2 rule. Anything dimmer won’t produce enough light to reach the lower branches sufficiently, especially on tall cannabis plants. Commercial cultivators can go over the 1000W range to maximize yields.

Photoperiod cannabis plants need at least 13 hours of light per day during veg. Having cannabis grow lights on for less than 12 hours could trigger premature flowering.

Indoor cultivators commonly use 18 hours of light per day to encourage faster growth in vegging photoperiod plants and from start to finish with autoflower strains. Most indoor growers veg for 4–8 weeks.

What is the best color spectrum for vegetative growth?

Blue light is essential for veg and flowering, but mainly for veg when the plant establishes structural growth. Red light promotes flowering, but too much red at the wrong time makes your cultivar stretch, resulting in tall, lanky plants and lower yields.

Some of the best light for growing plants indoors hardly have white light because it’s not essential, but have the right amount of required spectral wavelengths.

Can you use regular LED lights for grow lights?

Yes, you can use your everyday LED lights, if they deliver enough PAR light to your plants.

Unfortunately, regular LED lights usually only focus on lumens, and plants do not necessarily use the part measured in lumens. Lumens isn’t a good indicator of expected total production.

Get LED horticultural lights that are rated and tested to work on plants, in particular LED flowering grow lights with a red shade.

Finding the best indoor grow lights

Now you know what to consider when buying marijuana grow lights. Just to recap:

  • Grow lights vary widely: HPS types are cheap, but quality LEDs are the best option long-term.
  • Remember, plants grow best under specific light wavelengths.

Here’s our comprehensive guide for choosing the best LED grow lights—it’ll point you in the right direction. Happy growing!