Can worms live on grass clippings alone?

Here is a question from Jeremy:

I am planning on starting my own worm bin. The main reason I
would want to start one is that I mow my lawn every week and I have
nothing to do with all of my grass clippings. I have an average sized
lawn, about 5k square feet, and I mow once a week during the summer
months. I have thought about a standard tumbler composter for the
grass, but the idea of a worm bin really intrigues me. My main
question is this, can the worms survive, and hopefully thrive, on a
diet that consists mainly of grass clippings? Of course I will throw
in whatever food scraps I can and probably shredded junk mail. I was
just wondering if they can handle that bulk of grass weekly. Thanks.

Hi Jeremy,
This is a great question – I’m sure many other have wondered the same thing (or something similar anyway).
The short answer is probably “yes” – composting worms could likely be sustained on a diet of primarily grass clippings. There is however a very significant “BUT…” as well!

Here are some things I definitely would NOT recommend doing:

1) Using large quantities of grass clippings in an enclosed plastic (eg Rubbermaid) type of “worm bin”. Accumulations of grass clippings left to sit tend to turn into a wet slimy mess in some spots, and a dry moldy mess in others – neither of which are great for worms. Add to that the fact that this material has a pretty low C:N ratio and tends to off-gas ammonia when left to sit, and you can probably see why you wouldn’t want a lot of it simply sitting in a normal worm bin. Sprinkling in small amounts periodically won’t likely cause issues though.

2) Filling a typically backyard composter with grass clippings, then buying a pound of worms and adding them to it (assuming they will magically turn the material into beautiful rich worm compost). Based on what I mentioned in #1, it should be pretty obvious why this is not the greatest of strategies. Grass clippings alone are absolutely NOT an ideal Red Worm habitat.

Now that I’ve rained on everyone’s parade (haha), let’s chat a bit about how they CAN be used as worm food!

In all honesty, I think you were definitely onto something with your idea involving tumbling the clippings. A compost tumbler is a fantastic tool for getting materials ready for worm composting. If you mixed up a batch of grass clippings and shredded cardboard (moistened), fall leaves, or straw etc and let everything compost for a bit in the tumbler (turning periodically of course), after a week or two I bet you would be left with a really nice “worm food”.

Grass clippings CAN be use as-is, but the secret there is having a large, well-established (and high quality) worm habitat in place already. For example, I add grass clippings over top of my trench beds all the time, and they provide a great cover material and food over time. I have also added plenty of clippings to well established backyard bins containing lots of worms. In both cases, these are systems with excellent ventilation, and also systems with enough quality habitat down below that the worms can simply let the clippings rot, and come up to feed from below at their leisure.

Once you have a good (sizable) worm habitat in place, and you start layering the clippings over top, I am quite confident that you could continue to do so (and stop feeding them anything else), gradually creating a grass-only worm composting system – along with an associated population of composting worms well-adapted for this environment.

Now you’ve got me wanting to try this!! Perhaps I will add only clippings to one stretch of trench for the rest of the season and see what happens!

Anyway – I hope this helps, Jeremy!

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  1. Jeremy,
    I tried the compost clippings approach one summer with the same idea as you have. It did not work for me. Bentley is correct about the ammonia smell; I could not get it to balance.
    I dumped leaves, cardboard, and eggshell in my self standing, turn able, home made compost drum and all I got was Black Soldier Flies. I decided the grass clipping project was not for me or my worms. Besides it was a lot of work to haul that grass the compost drum, it is a lot easier to mulch the clippings and feed the soil directly.

    • Ashley
    • June 19, 2010

    Hi all. I run a small multi tray system and i have found adding grass clippings to be quite effective. however, the clippings i add have been left to age in an open heap for at least a few months. my approach was to fill one of the trays with the dry, aged clippings and to put that tray on the bottom of the stack. over time the clippings would absorb the leachate dripping through and the worms would start to move down into the tray rather quickly. the grass does take a lot longer to break down than the other trays, but I find i have a constant population of worms in the grass at any given time, and the amount of eggs in that layer is considerably higher than any other layer. also, given that my system is indoors, bringing the clippings from outside increases the diversity of critters in the system, which is great, because i end up with black soldier fly larvae in there too, and a few garden beetle larvae 🙂

    • Bentley
    • June 19, 2010

    Thanks for sharing, guys – very interesting!
    Ashley, you have raised a good point that I didn’t think to mention. There is a BIG difference between fresh green clippings and old brownish clippings that have been sitting around for quite some time. If grass is left to age for awhile it gradually becomes more like a “brown” waste material than a “green” – and as you’ve pointed out, when moistened in this state it is a great worm food/habitat.

    This likely helps to partly explain why clippings work well in my exposed outdoor beds – they basically sit on top and dry out for awhile before really getting mixed in with the straw etc below.

    Anyway – I am still really keen to see what happens if I add only clippings in one particular area (and no other food material)

    • LARRY D.
    • June 19, 2010

    One of the best purchases i ever made besides redworms,was a mulching mower.I found that when i raised the height of my mower,instead of shaving the grass to mow less often,and adding the grass back into the lawn,it cut down on weeds.Also looked better,took less water,and fertilization.And had less disease.The healthier grass cuts down on pests.But i do use my mower to mulch leaves to feed to the worms.Leaves piled up kills your grass!Experiment,but mulch mow your lawn!

  2. Larry,
    I do the same thing on my front yard. I am not a grass grower but, I will agree that the front yard does seem to retain more moisture to the point some mushrooms have popped up.

    • Bentley
    • June 19, 2010

    I used to be a die hard mulcher (and have always used mulching mowers), but ever since I created my trenches I just can’t resist the urge to add them (grass clippings) there!
    My lawn still seems to be doing just fine (no fertilization whatsoever) – I figure all the resources I’ve been bringing onto my “land” (haha), such as manure etc have served to boost the local ecosystems (bugs, birds etc etc), which in turn has resulted in more poop etc being deposited on my lawn.

    • Kuan
    • June 19, 2010

    My husband is a landscaper who also mows lawn, trim bushes, trees, etc. He has a bed full of grass clippings daily which he hauls to the landfill. I started doing hot composting in the back yard and have been using the composted grass clippings in my FT. In the Fall, there will be a mix of dry leaves with grass clippings. I either add a few handfuls of those or let them sit in the tubs or hot compost them. Although I can’t seem to use a significant amount of grass clippings that my husband brought home, I feel like I’m making a minute difference in terms of how much the landfill got.

    Grass clipping is fine for the worms as long as they are not fresh. If you really want to put grass clippings in fast, you can spread them thinly on the ground and dry them quickly. Then use them in the worm bin.


    • Chuck
    • June 19, 2010

    Last year I used precomposted grass clipping to feed my worms very successfully. I used a compost pile I turned over twice a week and left them for about 2 weeks. Basically until the heat died down. This I mixed with household garbage and the worms loved it. This year I decided to mulch mow to help my lawn. Now the worms get garbage and horse manure and love it too.

    • Chris B
    • June 20, 2010

    Here is an additional question… what about worms living in a plain old compost pile with leaves/grass/food waste etc. I turn it a couple of times a week and make sure it stays moist. Would this be a livable system for the worms outside of a bin?

    • John in Huntington Beach
    • June 21, 2010

    Chris B…

    That is essentially what I do now and my worms are thriving. I bury all the food waste in the worm side of my bin and put the fresh grass and leaves in the other. From time to time, I move some partially composted material to the worm side of the bin. The “fresh” side of the bin gets very hot but the worms move to the cooler periphery.

    My five foot wide bin has a piece of plywood which divides the bin into two roughly equal sides. The plywood is slightly smaller than the depth of the bin, allowing the worms to migrate from one side to the other at will.

    When I add fresh materiel, I let it sit a day or two to give the worms on the hot side time to “get out of Dodge.” Then I mix the material, after which the temperature quickly rises to 120-140 degree (F) range. I might lose a few of the critters but I think this is more than compensated for by the abundant supply of food that encourages breeding and hatching.


    • Michael from Roanoke
    • June 21, 2010

    Hello All,

    I was just wondering… I have plenty of grass clippings from my mother’s lawn, but the grass is periodically treated with pesticides, herbicides, and fertilizer. If I partially compost the clipping before adding them to the bins, will they still pose a threat to the worms?

    Best wishes, Michael.

    • Bentley
    • June 23, 2010

    CHRIS – Looks like John provided a great response so I won’t write too much. Basically what it comes down to is the temperatures in the pile. If you are turning it regularly, that to me sounds more like a typical hot compost pile. Worms do better in a heap that you slowly build over time and don’t turn.
    MICHAEL – I have heard of pesticides lingering even when materials are composted for extended periods (not just precomposted), so these clippings might not be the best choice for worm composting.

    • northson
    • July 5, 2010

    i am very interested in system designed to run exclusively on grass clippings. After six years of hobby herding i approached the superintendent at the local golf course about a beat up dumpster that looked a lot like a fine home for my worms.

    It now sits as a flow-through next to three steel drums i am using to pre-compost the clippings from the course. we have one drum at about 1.5 months one at 1 month and one receiving new grass. The highest recorded temperature for the first drum was 65 degrees Celsius. This was due to a spring application of high nitrogen fertiliser. we are definitely hot composting and our results look fantastic. i figure after 2 months or so we should be fine to feed the bin the composted grass – the temperature will tell us when it’s safe…or so i figure anyway – i won’t be feeding them till next year anyway

    our system is only 2/3 of the 15 square feet available and only at a depth of 6″ as we only had about 3k worms to start but they absolutely love the longer grass we raked up this spring mixed with equals parts shredded cardboard – this project was initiated is the hopes of using vc tea to combat snow mold – some very interesting information about vc’s contribution to soil profiles and disease management

    we expect to have a fully operational flow-through dumpster capable of processing at least 40 lbs a week by the first week of june next year (40+ below winters mean i will be emptying the bin in the fall)

    i tried to keep this short and left out some details but ya i’ve been following the site for a while and appreciate your efforts to get worms out of the closet and into the mainstream.


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