Updated July 5, 2023
Growing Microgreens and Wheatgrass can be some of the most rewarding small-scale gardening because your crop is done so quickly—and frankly, because it tastes so good! However, since growing Wheatgrass and Microgreens require a substantial amount of moisture, mold growth becomes a common occurrence. This causes many folks to become frustrated and even quit, unknown to them the simple steps that one can take to treat and prevent mold. It may sound easier than you think: control the moisture, control the mold.
Mold spores are everywhere! Even though we can’t see them, they are constantly wafting through the air—even as you read this. There is no way to “get rid” of mold spores. But no worries! Mold spores themselves are not inherently bad unless they find the ideal conditions to grow.
Not all mold spores are the same, either. Some grow on wood, food, carpet, and other various places. It is when the spores land on a damp surface to their liking and are exposed to continual humidity that they grow into the familiar spider web-like growth. It is also not uncommon to mistake the micro hairs attached to the roots as mold, but they are actually signs of healthy growth. Understanding this and the role moisture plays in getting mold spores started will give you all the knowledge on how to keep mold spores under control.
Healthy Root Hair Growth
1. Know your climate. Is it dry? Or is it humid? Sometimes you may need to adjust your care slightly based on where you live and whether you are using soil methods or hydroponic methods of growing. For example, higher humidity areas will absolutely require ventilation or a substantial amount of airflow. Whereas in dry climates, you may get away with less airflow. But, in dry climates, watering may be required more frequently rather than in humid areas. Basically, the trick is to judge what your tray needs based on what the soil or hydroponic growth pad looks and feels like.
2. Check your growing medium. Your soil or hydroponic pad should be moist, not soggy! Gently press your finger into it. Whether it is a pad or soil, the goal is to provide just what the plants need. Not too little or too much, but just right. When checking your soil or pad, it should be spongy—not muddy. You should be able to feel the moisture within the hydroponic pad or soil. It should not be secreted out. Water should not collect on the surface of your tray; it is the ideal environment for mold spores to land and spread. To avoid surface saturation, try bottom watering.
3. Keep the air moving. Keeping your air moving and ventilated is of the utmost importance because (a) it keeps the mold spores moving, giving them less of a chance to settle. (b) it helps keep the air from becoming stagnate and developing increased humidity. Open a window nearby during the day, and or keep a fan going on low in your growing space. Without proper airflow, your flat may appear dewy or give off a pungent scent.
If you find that your trays have already started growing mold, don’t panic. Just try all of the above tips to control the humidity and airflow of your growing space. Then, mix either a few drops of hydrogen peroxide or grapefruit extract into a spray bottle and mist your flat.
Soil may be a better option for high-humidity areas because it acts as a great regulator. Hydroponic pads tend to need more care as they don’t hold water as well as soil. So, try both and see which medium suits you and your growing style best!
12 comments
For people having issues I always mist my seeds from the start and my trays get watered in with a light amount of Dr. Zymes and I never have seen mold. Also VPD is very important for avoiding mold.
I have a question. You suggested grapefruit extract. Is this something you carry? Does it lower the pH? Can a pH reducer do the same thing?
Does any of the grapefruit extract absorb into the sprouts?
Use a high quality sugar, granular maple sugar or diluted blackstrap molasses 1-2 tablespoons per 2 gallon in a pump sprayer.
I spray the the trays after seeding them. After they germinate and I take them off the stack, I spray them again with the sugar water. This will feed the beneficial bacteria in the soil which in turn will keep mold spores in check. I’ve been using this method for my microgreen business for a year now with zero mold issues. Hydrogen peroxide is the worst choice because you are destroying all the beneficial soil bacteria and encouraging mold to take over. Anyone who uses hydrogen peroxide will notice a increase in mold issues.
Of course keeping your humidity around 50% with a average temperature of 65-70 degrees Fahrenheit is ideal for most microgreens.
Any temp higher than 75 Fahrenheit with higher than 65% humidity will make it more difficult. A great resource book to explain this more in depth is teaming with microbes by Jeff Lowenfells.
Happy Growing everyone 🌞🌱
Thank you for this article. I have been growing a variety of microgreens this past year and learning how each one grows plus experimenting with new ones. I have definitely had to deal with the mold issue. I realized I was watering too much but then when I slowed down too much my greens started drying up. I have started to learn the balance of watering and moisture on my soil. Some of my trays come out beautiful and some well, decide they want to play hard to get. Your article was spot on. I have made the peroxide mix and I see it work plus balancing the water and bottom watering. Sometimes I just spray them twice a day with a mineral water mix. I don’t use any chemicals or pesticides. Farm to table is my policy. Thank you for the grapefruit extract. I will have to try that one. Keep the articles coming. Happy farmer here.