Pest Control, Prevent Fungus Gnats on Houseplants

Fungus gnats are the little black bugs that tend to fly and jump around your house plants. As their name implies, they eat fungus that grows in the soil, and they tend to live near the top of the soil.

There are two principles in this instructable for maximum fungus gnat avoidance.

- adding a simple mechanism to water from the bottom of the plant

- reducing fungus by introducing a natural anti-fungal component, such as cinnamon bark

Some pots already provide a reservoir of water near the bottom, and are exposed to the air at the bottom which you'd water into. I've found this just moves the gnats from the top of the soil to the bottom of the pot, and not solving that problem.

What I've noticed works best (for me) is to have a closed bottom pot or bucket, with an aggregate on the bottom, and then a tube sitting on top of the aggregate. Watering is then done through the tube.

Step 1: Start With a Pot or Bucket

Find a clean pot or empty bucket.

If you're re-using a plant pot look for one that does not drain out the bottom. We're adding a tube to feed water from the bottom, which won't work well if the water just immediately drains.

Step 2: Add an Aggregate, Such As Rocks or Gravel

A rough aggregate, such as rocks or gravel should be added to the bottom.

With the pipe that will be added in the next step this will help with aeration and prevent stagnating water.

Don't make this layer too deep or the soil won't be able to wick it up. I use larger rocks for this reason as well, as some soil will go through the larger gaps to help with the wicking. You could add a strip of cotton (use a part of an old t-shit or old denim) that goes from the bottom to the top of the aggregate to help with wicking.

It's probably fine to skip this step.

Step 3: Use a Piece of Pipe, to Go From the Bottom of the Pot to the Top.

Use whatever leftover pipe you have, it doesn't need to be rigid. All you are really looking for is a way to pour water from the top and have it go to the bottom of the plant pot.

I used leftover ABS pipe from a previous plumbing project.

Step 4: Add Dirt on Top of the Rocks

Don't fill the entire pot with dirt, just put dirt on top of the rocks until it just covers them.

Step 5: Put in Your Plant, and Place Soil Around the Roots

Pretty simple, just put in your plants, and add soil around it.

In my case I'm replanting a plant that overgrew it's original container. I encountered two problems. The first was that there was a smaller plant as part of it that couldn't be separated from it's roots.

If you are replanting a plant that previously had gnats you should consider washing the old dirt on the roots off with warm water.

The second is that the roots for the larger plant grew on one side, and the roots were fairly rigid. Instead of planting in the center as I normally would, it was necessary to have the stem on the side so that the roots were taken care of.

Step 6: Add Cinnamon Bark (key Step)

Cinnamon is a natural anti-fungal.

Luckily Cinnamon bark is cheap and available (if you're in North America, like me, you'll find them in bulk grocery marts in the 'ethnic' / 'asian' sections ).

This is the double-whammy.

We're choosing cinnamon bark because: