Garden · Vermicompost

Vermicomposting Moisture Levels

This is one of the problems I ran into when first starting my worm compost bin. I had read that the bedding and food material should be damp like a wrung out sponge. That is correct. But I had also read from many sources that extra water is usually not needed because the moisture from the decomposing food should be enough to maintain a good moisture level for the worms. This is what caused my problems.  I didn’t take into account that I live in a desert. It’s dry and hot here and I keep my worms outside most of the year. Moisture quickly evaporates even in an enclosed worm bin. I was also not feeding them as much or as often as I should have so enough moisture wasn’t being added through the food.

Once I lost all my worms due to those and probably a few other problems, I realized that I needed to toss what I had read out the window and find something that worked better for me. Here are some tips about moisture that may save you some headaches and worms. Even though I’m thinking mainly about moisture while writing about this, these are also ideas that come into play with other aspects of vermicomposting.


Worm Factory 360 with 4 trays
Worm Factory 360 with 4 trays


Freeze and thaw veggie scraps. This helps start the decomposition process and releases the water in the food. Let the food come to room temperature before giving it to the worms.

Feed smaller amounts of food more often. A large amount of thawed veggie scraps releases a lot of water which can add too much water to your bin at one time especially if you have a small setup. Draining these scraps wastes that water and probably a fair amount of nutrients as well. In a desert climate, the bin could also dry out if the feedings are spaced to far apart.

-Too much moisture? Mix in extra dry bedding to soak up the excess moisture. Corrugated cardboard does a great job and worms like to lay their cocoons in it.

-Too little moisture? Add more moisture rich food scraps such as tomatoes, melons and cucumbers. You can also spritz the bedding/food material with water or use the mist setting on a hose nozzle. Add a few layers of moist newspaper on top to help hold in moisture.  In the summer, I have to give them extra water nearly every day.  If your water source is chlorinated city water (like ours) you may want to use bottled water or let the water sit overnight to off gas the chlorine. Off-gassing is recommended for making aerated compost tea because chlorine is harmful to beneficial microbes. So, it would also make sense that chlorine can be harmful in vermicomposting because those beneficial microbes are an important part of the process.

-Change of location. If you change the location of your worm bin it may affect the moisture. Bins that are kept outside will dry out faster. Bins that are kept inside will be easier to flood. Keep a close eye on your worms when you change locations so that you can act fast if a problem arises.

-Leachate. This is the liquid that comes out of the drainage holes in the worm bin. Some people call it worm tea but it is not. There seems to be a lot of disagreement as to whether or not worm leachate should be used in the garden. Without getting into that debate, I’ll just say that if you have a lot of leachate then your worms are probably drowning. Your bin is too wet. This is especially true of a tray system where the excess moisture drains through several trays before getting to the drainage holes. The tray at the bottom of the system can get very wet before you start seeing leachate.

When reading gardening articles or books it is best to keep in mind the location of the author. What works in one climate often does not in others. The same goes for vermicomposting especially when you keep your worm friends outside. Worms in the desert can dry out quickly when following advice written by someone in a more moderate climate. They can also flood easily if you don’t change your routine when bringing them inside.  Be quick to change if things don’t go as expected.


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