Root Hairs or Mold? The Microgreen Mystery Solved!

You’re excited about your first batch of microgreens, but after the blackout period, you spot white fuzz on the stems. Panic sets in—did your microgreens get moldy? Don’t worry! Most likely, the white fuzz you see are beneficial root hairs, not mold. We’ll explain the difference between root hairs and mold to ensure you’re growing and eating healthy, tasty microgreens.

If you've ever grown microgreens, you might have noticed a fluffy white fuzz near the base of your plants and wondered, "Is this mold?" This is one of the most common questions we get from new microgreen growers. The good news is, in most cases, it's not mold—it's root hairs.

Seeing the difference between root hairs and mold is hard until you look at an exceptionally focused photo. We’re sharing these pictures from some of our recent microgreens to better explain the difference between mold and root hairs. Once you know the difference, you can confidently grow microgreens and enjoy their excellent health benefits.

You can see healthy root hairs on the cabbage microgreen seeds in these photos. Isn’t nature beautiful?

First, it’s helpful to understand what root hairs are. Root hairs are tiny hairy fibers that extend near the end of the roots. These tiny filaments will take in water and nutrients to feed the plant. They can also help stabilize the plant in the soil. The root hairs are very helpful in ensuring the small plant is getting the nutrients it needs for rapid growth.

Usually, you never see these tiny root hairs. When you plant seeds into the ground, the roots go down, and the seeds send their green growth upward. But when you grow microgreens or sprout seeds on top of the soil or without any soil at all, you will see these white hairy fibers.

At first glance, it can be alarming because root hairs look a lot like mold, which you would find growing on those cucumbers you forgot about in the back of your fridge. However, healthy microgreen seeds will have these natural root hairs as they grow and search for water and nutrients.

The most common time to see root hairs is when you first take the lid off a tray of microgreens after the blackout period. As soon as the seed sprouts, it sends out a root, and the root hairs grow in search of nutrients.

As your microgreens continue to grow, root hairs will disappear into the soil, but mold will continue to grow on the surface and onto the seedlings.

Mold on microgreens should be a rare occurrence. Mold is caused by pathogens that can come from the container, soil, or air. These pathogens or fungi can also cause damping-off in seedlings. Like other moldy foods, microgreens with mold shouldn’t be eaten.

The location of the mold can be an identification clue. While root hairs will only be on the roots, mold can grow and spread on other parts of the plant.

Color and texture can also help you identify mold. Mold can be white and look like spider webs or cotton candy. It can also be other colors and textures. It is most likely mold if it has an uneven texture and is slimy or powdery.

The mold may also have a bad smell. When you brush across them, healthy microgreens should smell like their specific adult plant.

There are three main things to note that will help you correctly identify root hairs vs mold—color, texture, and location.

• Usually appear in the blackout period
• Looks like fine fuzz on the roots
• Bright white color
• Uniform texture that clings to the roots

Root hairs are normal and a sign of healthy seed growth.

• Usually appears after the blackout period.
• Often spreads unevenly over the soil or stems
• Color can vary from white to gray, green, and black.
• Slimy or powdery texture.

Mold is a sign of unhealthy microgreens and shouldn’t be eaten.

This example of peas shows the discoloration and fuzzy spots that are not on the roots.

We suggest these helpful tips to help prevent mold from growing on your microgreens.

Always start with clean trays. When reusing trays, use a bleach, vinegar, or hydrogen peroxide cleaning solution. (Use only one of these at a time, as a combination can create a toxic situation.)

Coconut coir or a sterile seed starting mix are good options for growing microgreens. Garden or used potting soil is more likely to have mold spores.

After the blackout period, ensure microgreens have adequate airflow while greening up. We don’t have problems with small trays, but the air can be stagnant when microgreen growers have multiple large trays. It can be helpful to set up a small fan nearby.

Microgreens need just enough moisture to sprout. The soil shouldn’t be dripping wet. A nice misting from a spray bottle should be sufficient to get them started. You can check them daily during the blackout period. Once they are growing, you can water from the bottom to keep the greens dry and the soil moist.

You can read more about the specifics of growing each variety of microgreen seeds. 

Microgreens are one of our favorite things to grow, and we eat them in a variety of ways. We love their taste and all the nourishing vitamins and minerals. The last thing we want is for you to be discouraged by having contaminated microgreens.

We know it can be alarming to see white fuzz on your microgreens. Even if you’ve grown lots of seeds, this may be the first time you’ve noticed root hairs.

It’s reassuring to know that white fuzz on microgreens is not always mold. Most likely it is the fine root hairs that are spreading as they get ready to nourish the plant in the soil. Because microgreens are planted on top of the soil, you are more likely to catch them at the point where the root hairs are easy to see before they’ve disappeared into the soil.

Now that you know the difference, these photos can help you correctly identify whether you have mold on your microgreens or root hairs.

Remember to use fresh microgreen seeds from Sow Right Seeds for guaranteed success.