Tips For Preventing Toilet Paper Tubes From Molding When Growing Seeds

Toilet paper tubes are biodegradable and cheap, and they're a great alternative to seedling pots that you already have in your home. Unfortunately, gardeners everywhere are also prone to getting moldy. And fast. Before you throw the whole concept out the window, hear us out because the mold is preventable — and it starts with not overwatering.

Typically speaking, seedlings need very frequent watering, but seedlings that are growing in toilet paper tubes have slightly different needs. When cardboard gets wet, it holds moisture like a sponge, which will keep the soil moist, too. This can easily lead to overwatering, which creates the perfect soggy conditions that mold needs. Instead, it's recommended you base water your seedlings multiple times a week. To do this, place the toilet roll tubes on a flat surface like a water-drip tray or a repurposed milk carton, then add water to the base (under the tubes, not over them) to allow the roots to drink from the bottom up.  

Another good idea is to let the tubes breathe. Good air circulation is often overlooked but it is crucial to avoiding mold. So, while covering your seedlings after planting is usually good practice, this time, bypass the plastic domes and make sure you have a window cracked open for a breeze. Mold hates moving air. Your seedlings, however, will thrive with a bit of wind in their leaves.

What you do before sowing your seeds also makes a difference in preventing mold and mildew. Bathrooms are wet environments, so if you take the cardboard tube straight out of an empty roll from the bathroom, there's a chance it may still be a bit damp. To avoid this, let your toilet paper rolls dry out completely — leave them for a few days on a sunny windowsill to get them nice and dry before sowing any seeds into them.

Once you're ready to sow, cutting the bottoms into flaps and folding them shut probably seems logical, but doing that will actually slow the drainage (which may increase the chances of mold). Instead, you're better off leaving the tube open and setting it down in a shallow layer of soil in a water-catching tray. This simple step means any excess water can drain out rather than hanging around at the base, increasing the likelihood of mold appearing. The final step to ensuring your toilet roll seedlings are happy and mold-free is to opt for a light seed-starting mix with good drainage. Heavy soil just holds too much moisture, and the tubes will take forever to dry out, which mold loves. A fluffy and well-aerated mix will dry out faster.

In summary, keep the soil dry and the environment breezy to make sure mold has no reason to think it's invited to your seedling party. And when it's finally time to move your seedlings outdoors, don't forget to start to harden them off gradually — there's no point avoiding mold just to have to deal with shocked roots later down the line.