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How to Avoid Mould in Microgreens: 7 Proven Techniques for Healthy Harvests

how to avoid mould in microgreens

Mould in microgreens can turn an otherwise delightful gardening experience into a disheartening struggle.

I know because I’ve been there.

But don’t fret, learning how to avoid mould in microgreens is simpler than you might think.

That’s why I’m here to help.

First, we’ll learn how to distinguish mould from harmless root hairs, a common mix-up for many.

If it’s mould, don’t worry, I’ve got you covered. I’ll guide you through effective ways to eliminate it and share my tried-and-true techniques to prevent its return.

Together, we’ll ensure your microgreens stay healthy, lush, and mould-free.

What Does Mould Look Like On Microgreens?

First, you need to be able to identify mould.

It’s crucial to distinguish between mould and other natural growths like root hairs. Let’s delve into how you can tell them apart.

Is This Mould or Microgreen Root Hairs?

When you spot something fuzzy on your microgreens, it’s easy to jump to the conclusion that it’s mould. However, it could be microgreen root hairs, which are completely normal and harmless.

Mould appears as a fuzzy or slimy coating and can be various colours like blue, purple, white or even black. In contrast, root hairs are thin, white, and usually spread out evenly throughout the root system.

Root Hair Examples

Root hairs on microgreens appear as thin, white, hair-like structures emerging from the roots. They are typically most visible just above the soil line. These root hairs are essential for the plant, helping to absorb water and nutrients.

  • Location: Root hairs are found close to the root and growing medium.
  • Appearance: They are uniform, thin, and hair-like.
  • Growth Pattern: Root hairs grow along the root and don’t spread to the leaves or stem.

How to Identify Mould on Microgreens

Mould, on the other hand, has a different appearance and behaviour:

  • Colour and Texture: Mould often appears as a fuzzy, cottony growth. It can be white, grey, green, or even black.
  • Growth Location: Mould can grow on any part of the microgreen, including leaves and stems.
  • Spread: Unlike root hairs, mould spreads rapidly and can cover a large area of your microgreens.
  • Smell: Mould often comes with a musty or mildew-like odour, which is not the case with root hairs.

Understanding Mould and Its Causes

Mould can be a real nuisance when growing microgreens, but by better understanding its causes, you can take steps to prevent it. Let’s explore why mould forms and how to keep your microgreens healthy.

What is Mould?

Mould is a type of fungus, and like all fungi, it thrives in moist, warm environments. It reproduces through tiny spores that float through the air, invisible to our eyes. When these spores land on a suitable surface, such as your moist microgreens, they can start to grow.

Why is Mould Common in Microgreens?

  1. Moist Environments: Microgreens require a humid environment to grow, which unfortunately is also ideal for mould growth.
  2. Dense Planting: Microgreens are often grown very densely. This high plant population in a small area creates a microenvironment with limited air circulation, which can promote mould growth.
  3. Organic Matter: Microgreens are grown in soil or soil-like substrates, which are organic and can be a food source for mould.
  4. Watering Practices: Over-watering or watering in a way that leaves the plants damp for extended periods can also encourage mould.

Now that you’re aware of the main causes of mould on microgreens, let’s see how you can prevent it.

How to Avoid Mould in Microgreens

Let’s dive into some key strategies to ensure your tiny greens grow healthy and mould-free.

Sanitize Trays and Seeds

  1. Start Clean: Always begin with clean, sanitized trays. Use a mild bleach solution or a natural disinfectant to kill any lingering mould spores.
  2. Regular Cleaning: After each harvest, thoroughly clean the trays before reusing them for the next batch of microgreens. I use a vinegar spray to clean my trays between each batch of microgreens.
  3. Disinfect Seeds: Soak your seeds in a vinegar-water solution or a commercial seed sanitiser. This step is crucial to eliminate any mould spores present on the seeds.

Use a Growing Medium with Good Drainage

Choose wisely: Opt for a growing medium that drains well yet retains enough moisture for the seeds to germinate.

Coconut coir or a well-aerated soil mix are good options.

Don’t Over-Saturate the Soil with Water

Moderation is Key: Water your microgreens just enough to keep the soil moist but not waterlogged. Over-saturation creates a breeding ground for mould.

I ensure the growing medium is moist before sowing, and then I hold off on any further watering until after the seeds have germinated.

Don’t Over Seed or Clump Seeds Together

Spread Evenly: Avoid sowing seeds too densely. An even distribution allows for better air circulation between the plants, reducing the risk of mould.

Only Water from the Bottom

Bottom Watering: Watering from the bottom keeps the top layer of the soil and the microgreens themselves drier, reducing the chances of mould growth.

Just fill your bottom tray with water whenever it’s empty. This way you will deliver water straight to the roots.

Good Ventilation

Airflow Matters: Ensure good air circulation around your microgreens. Use a fan or ensure regular air movement in the growing area.


Proper Lighting: Provide sufficient light for your microgreens. Good light not only aids in growth but also helps keep the growing environment less hospitable to mould.

Remedies for mould on microgreens

Discovering mould on your microgreens can be disheartening, but it’s not the end of the road. There are several remedies you can try to salvage your crop and prevent future outbreaks. Let’s explore some effective treatments:

Hydrogen Peroxide

Mild Solution: Mix a solution of food-grade hydrogen peroxide with water (typically a 3% solution is recommended).

Application: Gently mist your microgreens with this solution. Hydrogen peroxide is effective at killing mould spores without harming the plants.

Remember to rinse the plants with water afterwards to avoid a strong vinegar taste on your microgreens.


Natural Disinfectant: Sunlight is a natural mould deterrent. If you notice mould, move your microgreens to a sunnier spot if possible.

Exposing your microgreens to proper levels of sunlight can help prevent mould growth. Sunlight helps keep the plant’s surface dry and can inhibit mould spores from growing. If your greens are indoors, using a grow light near them can be a good alternative to natural light.

Duration: Letting your microgreens get a few hours of direct sunlight can help kill the mould and prevent its spread.


Vinegar Spray: Create a diluted vinegar solution (one part vinegar to three parts water).

Spray and Air Dry: Lightly spray the affected microgreens. The acetic acid in vinegar can help control mould growth. Ensure good air circulation to allow the microgreens to dry after spraying.

Grapefruit Seed Extract

Natural Fungicide: Grapefruit seed extract is known for its natural antimicrobial properties.

Making the Solution: Mix a few drops of grapefruit seed extract with water and spray it on the affected areas. This can help in controlling mould without using harsh chemicals.


Tackling mould in your microgreen garden might seem challenging, but armed with the right knowledge and tools, it’s a battle you can win.

Remember, prevention is your strongest ally – by creating the right growing environment and staying vigilant, you can significantly reduce the risk of mould.

If mould does appear, don’t be disheartened. Remedies like hydrogen peroxide, sunlight, vinegar, and grapefruit seed extract can help you salvage your crop and learn for the next planting.

So keep growing, keep learning, and enjoy the rich, green bounty of your efforts!

How To Avoid Mould in Microgreens – Frequently Asked Questions

How can I prevent white fuzz on my microgreens?

White fuzz on microgreens is often mistaken for mould, but it’s actually root hairs. To actually prevent mould, improve air circulation by using a fan and avoid over-watering.

What are the best watering techniques to deter mould growth?

Watering from the bottom and misting lightly can help prevent mould. Don’t over-water, and ensure proper drainage in the growing medium.

How can I keep microgreens mould-free at home?

Keeping your growing area clean and well-ventilated helps. Control humidity and use sterilised equipment to avoid mould growth.

What steps can I take to make microgreens last longer?

To make microgreens last longer, reduce moisture and humidity levels. Store them in the fridge with a paper towel to absorb excess moisture.

How can I safely sanitise microgreen seeds before planting?

Safely sanitise seeds by soaking them in a solution of water and food-grade hydrogen peroxide for a few minutes. Rinse with clean water before planting.

Should I eat microgreens if they have mould on them?

No, it’s not safe to eat microgreens with mould. Discard any infected crop to avoid health risks.