Updated: Mar 13, 2020
The reason for writing the ultimate guide on preventing microgreens from drying out is to help prevent the several drying out problems that commonly occur when a grower starts a microgreens business. Imagine having Michelin star chefs waiting on specialty microgreens for their evening services and you come to your grow room early that morning, only to see all the microgreens dried out. This leads to several dreaded phone calls to the chefs letting them know, there are no microgreens to deliver.
In this guide, we'll cover four common issues that lead to microgreens drying out:
Improper humidity and temperature, poor choice of lighting, improper NFT maintenance, and choice of proper soil and/or hydroponic medium.
Now here's the guide so this doesn't happen to you:
Humidity & Temperature:
Harsh temperature and humidity levels tend to deter healthy microgreens crops and can dry out them when temperatures are high and/or humidity is low. Outer limits for all microgreens crops temperature ranges are from 50ºF/10ºC to 85ºF/29ºC and humidity ranges from 50% to 75%. Normally, most seeds do need warmth and moisture for germination, with ranges around 70ºF/ 21ºC to 85ºF/29ºC and 75% to 90% depending on variety. Controlling your environment is key to not letting your microgreens dry out. Installing a self-contained wireless data logger will help you keep an eye on your grow room with the convenience of your smart phone.
Microgreens need light to grow. Without light, photosynthesis cannot exist. Not only do different varieties need different amounts of light to thrive, finding the right type of light bulb can be difficult to ensure healthy microgreens.
Incandescent lamp is highly a inefficient light source, with a 100 watt bulb just 2.1% efficient. That means it produces about 2 watts of light and 98 watts of heat. This lamp can dry out microgreens within hours depending on your grow medium, temperature, humidity and distance to incandescent light.
T5 fluorescent lamp is an inefficient light source, with a 100 watt bulb at about 8% efficient producing about 8 watts of light and 92 watts of heat. This lamp can dry out microgreens within 24 hours depending on grow medium, temperature, humidity and distance to the T5 light.
LEDs lamps are a 30% efficient light source. They do not give off as much heat as the T5 fluorescent and incandescent bulbs. Because they're so energy efficient and provides bulb temperatures at 110ºF/43ºC, this lamp can dries out microgreens within 48 hours (or twice the amount of time of a T5 fluorescent lamp), again depending on grow medium, temperature, humidity and distance to the LEDs light.
Very little filtration is recommended in an NFT system, if the nutrient water does not contain solid particles, and if the process of supporting the microgreens does not discharge solid particles into the return tank. If there is a problem with solid particles in the nutrient tank, a inline filter should be installed on the 1/2" supply pipe between the main pump and the 1/16" inlet tube to the NFT channel(s). If there is a serious problem with the system clogging up, then the filtration can be done by using a mesh screen in your return pipe. The mesh screen and the inline filter have to be cleaned and replaced frequently.
Soil Versus Hydroponic Medium:
In general, microgreens will be healthier and taste better if grown in high quality soil. The sweetest taste often comes from soil that contains some beneficial bacteria-delivering bioavailable minerals in the soil. That being said, there is a lot of microbial activity happening in the soil that researchers are only now discovering. It is best to try a few different mixes to see which works best in your environment. Run test with two different soils. First fill one 10x20 tray half way, and fill a second 10x20 tray up to the brim with one soil mix. Check the trays daily to determine how many days it takes to dry out. Test other soil mixes to see which performs best. And remember, numerous microgreens can be grown without soil, and you can get a very gorgeous harvest from a good hydroponic system that contains proper nutrients and beneficial bacteria. Coco coir is a waste product of the coconut industry with ok water retention capacity and oxygen capacity. It is best to try a few different brands to see which is not high in sea salt and is very fine grained. Run the same test as described above to determine how many days it takes to dry out in your environment.