Vermicomposting Yard Wastes

An interesting message/question from Sam:

I just finished a large landscaping project where I removed a bunch of
clumps of dirt with weeds and grass in them and put them in a composting
pile. My town is really small and I dont know of any places to purchase
red worms but I would like to start composting as soon as I can. My first
question is do red worms eat/compost grass clippings like from a lawn mower?

Hi Sam,
This is probably something a lot of people have wondered about, so thanks for writing in!

I’m afraid this is a bit of a “good news/bad news” type of situation, though. While composting worms CAN process some yard wastes, including grass clippings, the materials you’ve described are definitely NOT ideal “worm foods”.

For starters, I would personally aim to keep as much soil out of the compost heap as you can (whether for vermicomposting or not). If a lot is added, it will only serve to impede the composting process. In the case of vermicomposting, it’s important to remember that these are not soil worms, so it’s definitely not their preferred habitat material. In moderation it should be OK, provided you’ve already established a good quality habitat for the worms.

Speaking of which…

When you’re attempting to process large quantities of yard waste (via vermicomposting), it’s important that you don’t use those materials as your starting place. Setting up a “home” for your Red Worms using a bunch of weeds and grass clippings, for example, is just an invitation for trouble. Most of these green wastes are nitrogen-rich (low C:N) and have a tendency to release some of this nitrogen in the form of ammonia gas, which is very toxic for worms. They also just generally tend to be poor habitat materials.

My recommendation would be to set up your outdoor worm bed in a manner similar to setting up a typical worm bin – i.e. by creating a mix of quality “bedding” and “food materials” (containing more bedding than food), and letting it age for a period of time before adding the worms. You may want to have a look at my very first “Vermicomposting Trench” article to get a better idea of what I mean (a trench might actually be a great approach in your case).

Once this “quality worm habitat” is established, and the worms have been added, you have a lot more options in terms of what you can add. By the way, if you are looking for a sort of “ultimate” composting worm food/habitat to help you get going quickly, some well aged horse manure will REALLY do the trick. Make sure it’s been sitting outside somewhere for a while, is fairly dark in color, and no longer has an obvious manure smell. This stuff is pure gold for outdoor vermicomposting projects.

Something you can do to make yard wastes much more “worm friendly” (and microbe friendly) is chop them up as much as possible before adding them to your system. A mulching lawn mower is an excellent tool for helping you do this. Just lay the wastes down in low rows and run over them with the mower (ideally, with catch bag attached). I’ve made some beautiful mixes of fall leaves and grass clippings this way, and even a nice mulch using old sunflower stalks. Usually the best bet for “feeding” these yard waste materials to your worms is to simply layer them over top of the established worm habitat I discussed earlier. This way you are not forcing the worms to feed on the yard wastes right away – they can do so once they decide they are “ready” (likely after they’ve been moistened, and partially decomposed by microbes).

By the way, this article may help as well:
Earth Machine Vermicomposting

Best of luck!

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