Microgreens are plants that are harvested young, usually right after they have developed their first true leaves and have reached a height between one to three inches tall. Growing them at home can be fairly easy for any gardener, as long as it is done correctly and in the right conditions. When it comes to light exposure, for example, although microgreens start growing in a dark environment, they will need access to an adequate amount of light at the right time.
When should microgreens be exposed to light? It is best to expose microgreens to light two to three days after sprouting is evident, or when they have grown to be about an inch-and-a-half tall. Allowing the microgreens to reach this height first will allow gardeners to harvest easily and yield more.
Just like any other plant gardeners would grow, microgreens require a specific amount of time in which they are exposed to the light. In addition, waiting too late to give them access to light or doing it too soon may affect the quality and yield of the microgreens at the time of harvest.
Why Microgreens Need the Dark
After sprinkling microgreen seeds over the chosen medium and initially watering, it is recommended to cover the tray used with a dark lid (e.g., blackout dome) or dish towel and maintain a warm, humid environment with plenty of airflow.
But why is this necessary? This step is important for the seedlings and their germination process, which usually takes between three to five days. When they are in the complete dark, the microgreens will have to stretch up as they sprout in an effort to locate a light source.
When to Expose Microgreens to Light
Generally, the ideal time to expose microgreens to light is two to three days after sprouting is witnessed, although this may differ between seed types. For example, some microgreen herbs may grow more slowly compared to other varieties, and therefore require extra time in the dark. Microgreens like broccoli and kale tend to grow more quickly, and as a result, only need about two to three days in dark conditions.
This time frame allows the plants to become “leggy” as they grow upwards in search of light. Once they have reached a height of roughly one to one-and-a-half inches, they are ready to be left under a light source.
The benefit that comes from delaying light exposure until this point is that a higher yield will likely be produced. Allowing microgreens to stretch will also ensure that the process of harvesting them is easier, as it will be easier to cut the plants closer to the medium and ultimately harvest more.
Waiting too long to expose the microgreens to light will eventually cause them to run out of energy to continue growing tender sprouts. The spouts will eventually become “limp” and start to fall over as a result.
On the other hand, exposing the plants to light too soon will trigger the photosynthesis process too early. The microgreens will develop their true leaves early on before they have had the chance to grow a long, sturdy stem, leading to a smaller yield by the time it is time for harvest.
For a detailed explanation of when to expose microgreens to light, as well as tips for some other common issues that occur in the growth of microgreens, check out this video from MIGardener.
In the same way, let your light shine before others, that they may see your good deeds and glorify your Father in heaven.
Matthew 5:16
The Best Light to Use for Microgreens
Like most plants, microgreens require light for photosynthesis. Besides natural sunlight, a selection of artificial growing lights can also be utilized. However, keep in mind that the lighting used will play an important role in growing healthy microgreens.
Sunlight
Of course, natural sunlight is most recommended for microgreen cultivation, but whether or not the plants will thrive more under direct or indirect sunlight will depend on the variety.
Direct Sunlight
Those who want their microgreens to have access to direct sunlight should be mindful of where they decide to leave them. Many gardeners choose to place them outside for four to five hours of the day so that they receive light while the sun is out.
Indirect Sunlight
In shadier yards, indirect sunlight may be the better option in terms of allowing microgreens sufficient access to light. Although, this may also be the case for gardeners who choose to leave their plants next to the window.
Many microgreen varieties prefer indirect sunlight over direct sunlight. Examples of a few that grow best under indirect sunlight include:
- Dill
- Cilantro
- Chervil
- Arugula
- Tat Soi
- Amaranth
Some lettuces, mustards, and pak choi varieties also grow particularly well under indirect sunlight and other low-light environments.
Window Light
Microgreens that are kept to grow indoors can access sunlight that comes through the windows, but, according to the Arizona Extension site, this may be insufficient, especially for certain microgreens. While microgreens such as lettuce, arugula, mustards, and Asian greens can grow just fine in low light, other varieties may not do as well.
Artificial Light
If the microgreens will not have enough access to any form of sunlight, then a specialized fluorescent or LED growing light can be used.
One benefit of using grow lights is that it is not necessary to follow the sun throughout the day. Merely set the lights on a timer so that they can turn on or off at various points of the day. The most important thing to consider with growing lights, though, is where plants are placed. Try to leave them in an area that is not easily disturbed. This way, the microgreens can grow in peace.
Fluorescent
Something like a T-5 or T-8 fluorescent light can help supplement or substitute sunlight if the microgreens do not have as much access to the sun. When using fluorescent lights, make sure to keep the light’s tubes more than two inches away from the plants to better provide the greens with equal light coverage.
LED
Light-emitting diode (LED) grow lights are nice for gardeners because they produce little heat, last for longer periods, and are energy efficient. They are also good for microgreens! They give off blue and red light, which is what plants love to absorb for photosynthesis. Red light aids in plant growth, while blue light helps improve leaf thickness and the number of chloroplasts present.
Many LED lights have a correlated color temperature (CCT) between 4000K and 6500K. However, since natural daylight is 6500K, it is best to find a LED growing light closest to that number.
How Long Should Microgreens Be Exposed to Light?
After the “dark” period, microgreens should be exposed to light to foster growth following germination. Gardeners using natural sunlight as the source of light for microgreens should be providing approximately four to five hours of direct sunlight—or eight hours of indirect sunlight—per day.
Note: Avoid giving microgreens too much direct sunlight because the heat can cause damage after long-term exposure.
The daily exposure to light should continue until the microgreens are about two to three inches in height or have developed their first true leaves (this can range between 7 to 21 days after they are planted).
Final Thoughts
Growing microgreens can be a complicated yet rewarding process for any home gardener. With the right lighting conditions and a little help from God, microgreens will grow at a healthy rate and can be ready to add to future meals in a matter of weeks.
If you are interested in getting started with microgreens or are looking for a reliable online store for seeds and supplies at a great price, check out our affiliate at True Leaf Market. TrueLeafMarket.com – Microgreens Seeds, Kits & Supplies
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