Why Do My Microgreens Smell? (Solved & Explained!)

Microgreens, grown properly, should have a fresh, vegetal smell. Some sprouts, such as broccoli, can have a sulfurous smell to them. If they begin to smell foul, it is likely that they have been overwatered, are overcrowded, subject to too high or too low temperatures, insufficient airflow, harmful chemicals, or high humidity. These factors cause them to develop mold and stem rot. 

In this article, we’ll detail why your microgreens might be smelling foul, what to do, and how to prevent mold in future batches. 

How can I tell if microgreens have gone bad?

When microgreens begin to decay, they will start to give off a strong, swampy odor. It should be easy for you to tell the difference between the decaying greens and any other smell they might have.

The stems will begin to grow mushy, and you may even see spiderweb-like mold growing in the tray along with your greens.

Can I eat microgreens that have gone bad?

If you notice that your microgreens have developed mold or root rot when you pick them, they are not safe to eat and should be thrown away.

If you see mold on any trays of still-growing microgreens, the entire tray should be thrown out. 

Can I save microgreens that have started to grow mold?

If you have noticed mold and caught it early, there is still a chance that they might be saved by spraying a mixture of 3% food-grade hydrogen peroxide and water on the greens. A vinegar solution made in the same way will also be effective.

You may also want to move them into direct sunlight, which mold hates. If you have noticed mold, however, don’t attempt to eat the microgreens raw, even after using this solution, and best practice is to abandon the tray altogether. 

How do I prevent mold from growing on microgreens?

To prevent mold, make sure your microgreens have proper drainage, the correct temperature and humidity, proper air circulation, and proper lighting conditions.

When you get your seeds, make sure to presoak and disinfect them before planting. Avoid seeding them too densely, as overcrowding can generate too much humidity.

In between seedings, make sure to properly disinfect your seed trays and flood trays.

What does mold look like on microgreens?

Microgreens have root hairs that can look like mold to the unexperienced eye. Root hairs help seedlings with nutrient uptake and will not have an odor. They appear feathery and only grow around the root of the sprout.

Mold appears as spider-web like strands growing directly on the greens and will have an offensive odor. It can also appear as black, blue, and purple spots on leaves. 

What causes mold on microgreens?

Moisture in the growing environment is the most common cause for mold. This can happen in a variety of ways. Poor drainage is often the issue, where frequent waterings are not allowed to drain through the soil whether through incorrect soil types or improperly draining trays, causing water to pool on the bottom of containers.

Humidity in the environment can also encourage mold to grow. Mold loves warm, dark, damp spaces, so improper lighting is also a contributor to mold growth. 

What type of soil is best to encourage proper drainage?

Not all soil is created equally. Don’t just use the first soil you find to grow your microgreens. They do best with soil that promotes drainage and air circulation, such as soils that contain a good ratio of perlite and peat moss.

If you are feeling ambitious, you may use coco coir, a sustainable alternative to peat moss that comes from coconut fibers, but make sure that you are adding extra nutrients in your water as it does not contain any.

Why should I disinfect seeds before planting?

Some varieties of microgreen seeds are notorious for being “dirty”, that is, carrying seed-borne diseases that result in mold, root rot, and ultimately tray loss. Disinfecting the seeds stops these diseases before they start.

Cilantro, peas, and sunflowers are a few that benefit from a pre-soak and disinfection with H202 prior to planting. 

What is bottom-watering and why should I do it?

Bottom-watering is an effective way to prevent standing water on leaves and stems, which can cause mold and rot. Simply place your microgreen container into a bowl or small tub that has been filled with water.

Make sure the water is half as deep as the container. This causes only the soil to come into contact with water.

When the soil is dry, simply fill the tub again.

How do I clean my growing trays?

Clean trays are vital to prevent mold when attempting to grow microgreens. Between plantings, make sure you are washing and sanitizing your trays. Even if the prior growing didn’t mold, residual bacteria can cause mold on a new batch.

Wash your trays with a mild detergent, clean out all residual root material, rinse thoroughly, spray trays with a diluted vinegar OR peroxide solution (make sure to use food grade peroxide only!), rinse well, and let air dry. 

What about root rot?

Not all smelly microgreens are caused by mold. The roots can also rot due to high humidity, lack of ventilation, or heat stress. The greens will begin to have a swampy smell.

Like moldy greens, those with root rot will not be safe to consume. Look for the offending stems and if it hasn’t spread to the rest of the tray, remove them.

If you’re inexperienced with addressing root rot and saving trays, it is best to throw out the entire tray and start over, just to be safe. 

Are my stored microgreens bad?

You may have completed a successful planting and picked your greens, only to find them in a sorry state when it comes time to eat them. Microgreens can go bad very quickly once they have been picked, so be sure to eat them within a few days.

To prevent this, make sure you are storing them completely dry. Any water present during storage will cause them to go mushy and begin to rot. Don’t go through all the work of growing microgreens just to let them rot once they have been picked!