Lights for growing microgreens?

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The good news about microgreens is that they do well under a variety of light sources. This means it is easy to start where you are and add on as your needs and your available funds increase. A few trays in a sunny window for the home grower, up through multiple vertical rack systems with dedicated growing lights for commercial production.

The question of which lights to use can be complex and depends on a lot of factors.

Are you growing for home use or commercial sales?
How many trays are you growing?
Do you have access to sunlight, IE. greenhouse or sunroom?
Are you planning to grow year round?
Do you need reliable harvest times or are you more flexible?
How much money can you invest in your light system?

Here we will go over the most popular lighting options from lowest to highest in terms of cost and list some of the pros and cons of each.

Lighting Options for Growing Microgreens

This is, of course, the cheapest and most complete spectrum light source available. For the home grower, any sunny window sill or small greenhouse can be used to grow microgreens. In larger scale operations greenhouses or high tunnels with tables can be used to grow microgreens when limited space is not a concern.

Pros: Free, readily available, no wiring or timers needed, complete light spectrum in the 6500k range on a clear day.

Cons: Inconsistent due to seasons and weather, produces heat that can affect growth, does not work well in vertical rack systems, requires supplemental lighting in winter months.

The first 6 months that I was experimenting with microgreens I grew in a high tunnel using available sun and no supplemental light. If you have plenty of table space and some flexibility on harvest times this can be a great way to grow microgreens.
Fluorescent Shop Lights
Fluorescent lights are similar to LEDs in light production but use more power to run and produce more radiant heat so we don’t recommend them here. They also regularly contain mercury which can contaminate your grow area if the bulbs are broken. If you are using existing fixtures we recommend replacing the CFL bulbs with LED.
LED Bulb Shop Lights
These can be purchased at most big box stores for around $20 a piece. They are a standard 4’ long. These make an excellent trial light when you are ready to try growing indoors or need to go with a vertical rack to increase growing capacity in a limited footprint.
Pros: Inexpensive, easy to find, acceptable light spectrum 2200k-4000k for microgreen growth, produces minimal heat, can usually be daisy chained 3-4 lights, works with 120v household electrical outlets.
Cons: Bulbs are often unprotected from water and dust making them susceptible to damage, brands vary greatly in quality, normally designed to be installed horizontally only, less efficient than strip LEDs, generally last far fewer hours than strip lights, light spectrum too low for longer growing crops (this shows as discoloration in the leaves in later stages of growth or plants becoming too leggy and falling over before harvest).

All of that being said, I have been using the original 5 of these that I started out with in my growing room for 2 years now. They work fine for the shorter growing cycle crops but I found that micro herbs and longer growing cycle crops needed the higher light spectrum available in the LED Strip Grow Lights to reach potential.
LED Strip Grow Lights (T5)
Dedicated grow light strips are usually sold in the same standard 4’ as shop lights. Full spectrum, above 5000k strip lights run from $75 up to $650. Most of these offer a growing area of 4’x2’. They can come with or without the surrounding reflector that gives it the classic shop light shape and helps redirect light increasing efficiency.

Pros: Moderately expensive, can be found in hydroponic stores and online, full light spectrum 4500k and above allows for longer growing periods, produces minimal heat, efficient watt to lumen ratio, the good ones offer lighting surfaces that are protected for dust and water, can usually be daisy chained up to 7 lights, most work with 120v household electrical outlets, some can be installed vertically if needed for your set up.
Cons: Moderately expensive(pro or con depending on your situation), quality, efficiency, and longevity can vary greatly between brands.

These are the most commonly used lights in vertical growing systems. We offer a self contained (light, plug and reflector) option in our store.
LED Panel Lights
These are the top of line growing lights for indoor use. They are generally used in larger scale commercial growing of plants that need to reach full size or produce flowers indoors. The high light intensity could be considered overkill for growing microgreens. Ranging in price from $99 into the $1,000s they can be very expensive for the limited growing area. Growing area covered is typically 3’x3’ for smaller panels up through 8’x8’.

Pros: Come in a variety of sizes, intense full spectrum light capabilities, variable sizes for customized growing spaces, highly efficient watt to lumen ratio.

Cons: Expensive, thick profile limits their ability to work in vertical rack systems, generally require separate ballasts for electricity, must be purchased from specialty suppliers online or in hydro stores if they are available in your area.

How far should my lights be from microgreens?

This depends on the light source being used because heat generated by the lights can burn microgreens if placed too close. Most LED strip lights do not generate enough heat to cause problems and do well 6-12 inches from the surface of the growing greens. The farther the greens are from the light source the more they will “stretch” and become leggy. That said I have definitely let my peas grow a little too tall and touch the lights without any damage to the greens.

Panel lights are higher intensity and can be placed farther from the growing surface without too much light loss.

How Many Hours of Light Do Microgreens Need?

There are as many opinions on this as there are growers to have them. General rule is that plants need AT LEAST 6 hours a day of light to grow. If you are using sunlight as your main light source, you are of course limited to the hours available to you. Being aware of shade patterns and light direction when setting up your system can help you get the most from your hours.

Indoors you have the control to experiment with what works best for you. Some growers keep lights on 24/7 to speed growth. Others use a modified daylight schedule of 12 hours on 12 hours off. Personally I use an 18 hour on 6 hours off. Here there is a happy medium between extra light hours to speed growth and allowing the plants “resting” time. I find that the colors and flavors just seem better when the plants are allowed rest in the growing cycle. Experiment with different light cycles and see what works best for you.
A note on light spectrums- most lights will be labeled between 2000K to 6500k.

The lower end of this scale, color temperatures from 2000K to 3000K, are referred to as “warm white” and range from orange to yellow-white in appearance.

Color temperatures between 3100K and 4500K are referred to as “cool white.” This range will emit a neutral white light.

Above 4500K will give off a blue-white light that mimics daylight.

Because most microgreens are grown for short periods of time the light spectrum is less important than plants grown longer or into a flowering stage. In growing micro herbs or other plants longer than 20 days it is advisable to use lights that produce a color temperature above 4500k.

Lumens to Watts is another phrase you will see in a lot of light comparisons. This refers to the amount of light produced per watt of electricity used. LEDs are the most efficient by far.
Let us know if you have any questions or comment below what systems have you tried?
What worked best for you?