7 Ways On How To Prevent Mold With Seedlings In Small Greenhouse

Are you wondering how to prevent mold with seedlings in small greenhouse? You will be confronted with a lot of considerations, including the temperature, airflow, and light that enters the greenhouse. Also, you have to consider the spacing of the seedlings inside their tray and the amount of water you give to your plants.

Molds that grow on your seedlings do not harm the plant. Its growth is more of an indication that your soil is too wet. Overly moist soil can quickly rot the fragile roots of the seedlings. If the roots are dead, eventually, the rest of the plant will follow.

how to prevent mold with seedlings in small greenhouse

This article will present to you seven ways on how to prevent mold with seedlings in small greenhouse.

Steps To Prevent Molds On Seedlings

Now, it’s time for you to learn how to prevent mold with seedlings in small greenhouse. In this section, we have compiled the necessary steps so that everything will be easier for you. Just read on!


#1 Temperature management

There is a range in temperature in which your plants can best photosynthesize. Keep the temperature inside your greenhouse between 77 to 82F. Anything above this can overheat your plants, especially if there is a heating mat present under the seedlings.

So, the first thing you need to do on how to prevent mold with seedlings in small greenhouse is to manage the temperature.


#2 Water management

The most common reason why molds grow on seedlings is because of overwatering. Since watering is an essential task done to help seedlings sprout, people tend to forget that giving plants too much water can harm them.

To solve this problem, use your finger and determine if the soil is dry. If it is, then that is the time you should water your seedlings. Simple and easy, but often neglected.

Another way to prevent overwatering is by applying the water from the bottom system. This type of watering system ensures that the top part of the soil remains dry while the roots get to soak in the water from the bottom.

Do not leave the water under the tray for too long, though. Make sure after 30 minutes, you throw out the remaining water inside. Keeping stagnant water will damage your plant more than benefiting from it.

If you already understand how to manage water for your plants, you can deal with how to prevent mold with seedlings in small greenhouse.


#3 Provide better air circulation

The best way to prevent mold growth is by improving the air circulation inside your greenhouse. Install an oscillating fan in the greenhouse and let the air blow directly on the seedlings. If you have a cover laid over your seedling trays, don’t forget to open them up so airflow can increase.

Having good air circulation has more benefits than just keeping your soil dry and preventing mold and fungal growth. It also helps the plants get stronger. That is why we highly recommend this advice because you get more benefits than one.

When you do follow this recommendation, pay close attention to the moisture level of your soil. The soil dries up quickly when there is a fan present. Yes, you need the soil to be dry, but not to the extent that there is no moisture left.


#4 Provide better lighting

The basic needs of a plant are water and sunlight. In this case, though, avoid letting your seedlings be under direct sunlight, especially when you have covers over the trays. Covered seedling trays trap the heat inside, therefore making the environment too hot, which damages the seedlings.

On average, per day, most seedlings need a few good hours of robust and indirect light. Research more on how much indirect light does your seedlings need so you can be confident about how long you will let it be under the light.


#5 Thinning out the seedlings

Overcrowding of seedlings can lead to less air circulation within your plants. And as we have stated above, one great way to prevent the growth of molds is with proper air circulation.

A way to solve this problem is by thinning out your seedlings. This method means pulling out a few seedlings from their trays. It gives more space to your seedlings to grow and avoids the crowding situation.

Here are the ways on how you can thin out the seedlings:

1. Repot your seedlings

Thinning out is more of removing seedlings and throwing them away while repotting is about transferring them to a different pot. Once you’ve correctly extracted the seedlings from the main tray, you can replant them in a reusable plastic pot and let them grown in there.

Other than plastic pots, there are many other sustainable options you can choose from, depending on your preference. In times today, people have been innovating plantable pots for convenience and sustainable purposes.  There is even a pot made from cow manure.


2. Disinfecting seed flats

Other than paying attention to the seedlings and its soil, inspect your seed trays for mold growing on it. There are mold spores that become dormant in the seed flats and then regrow after a while.

To avoid such complications from happening, always disinfect your seed trays after every use. Do not just keep on replanting on your trays without making sure that no mold spores are growing in them.



We have listed here seven excellent ways on how to prevent mold with seedlings in small greenhouse. It tackles the different problems and gives proper solutions to each one of them. With this knowledge, you won’t be able to see molds on your seedlings any time soon.


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