Grass Clippings as Worm Food

When people ask about using grass clippings (and green yard waste in general) in their vermicomposting systems, I tend to offer them fairly cautious advice. This is definitely NOT a material I consider to be an ideal worm food for the beginner vermicomposter. That being said, it’s potential as a worm food in general need not be ignored.

First, let’s examine why grass clippings can be a challenging material to work with.

For starters, this material has a low C:N ratio (approx 20:1 or so) and breaks down quite quickly – interestingly enough, these characteristics actually contribute to making this a valuable materials as well (we’ll talk more about that in a minute).

The potential issue here is that rapid breakdown of low C:N wastes can lead to the release of ammonia gas, which is very toxic for worms. Rotting grass clippings also tend to get matted together, becoming a bit of a slimy mess.

Another issue with this material is that it doesn’t hold moisture very well – at least not until it is well rotted. Since worms thrive in very moist conditions, the ‘habitat’ value of rotting grass (on its own) is very low.

Add to this the fact that grass can have pesticide and inorganic fertilizer residues on it, both potentially hazardous to worms. This is why I wouldn’t likely ever use grass coming from unknown sources (ie the stuff collected by landscapers).

Moving on to the positive aspects of grass clippings…

As mentioned above, the fact that grass breaks down quickly and has high N content can actually be a good thing, since this makes the material an ideal ‘microbe food’ (and we know how much worms love a diverse microbial community).

So how do we compensate for the low C:N and the poor moisture holding issues?

By mixing it with an absorbent C-rich material, of course!
🙂

Those materials I typically refer to as “bedding” are great for improving the food and habitat value of grass clippings. Bulky materials like shredded cardboard and shredded newsprint would have the added benefit of greatly increasing air flow as well.

My recommendation would be to simply mix your clippings with your bedding in a 1:1 ratio, soak everything (ideally in a location where excess moisture can drain away), then leave the mix to sit for a week or so.

You can also mix grass with other ‘brown’ wastes, such as straw and fall leaves, but you may need to let them rot longer in order to improve the moisture holding properties of the mix.

It is important to mention that this method is certainly not the ONLY way grass clippings can be successfully used as a worm food. In all honesty, my typical approach involves adding clippings in very thin layers to the top of my outdoor vermicomposting systems (such as my trenches). Since these systems are already well-established, there is no chance the clippings are going to create any issues – they can simply rot on top (and help to keep moisture in), and the worms can come up to feed on the material once it’s ‘ready’.

I haven’t really used grass clippings very much in indoor systems – this is definitely a bit trickier, especially when using enclosed bins. I do have plans to test this out though. I am planning to set up a system and use ONLY grass clippings as a food source (while it is available anyway), once the main ‘habitat’ is set up. I’m curious to see how well worms grow with a solely grass diet.

Stayed tuned!
8)

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Comments

  1. What I do with my grass clippings is, I have a compost “tumbler” that I add the clippings to. I let the clippings “heat” up or pasturize in the tumbler till they smell really bad, then I add some news paper then turn it. I check it for three days to reduce the smell, turning it frequently. Sometimes I add peat moss to speed it along and I will add pulverized egg shells for the heck of it. After about two weeks I will start to use it for feedstock.
    In the summer months, I try to reduce the heat energy from the decomposition process from my feedstock so my bins won’t heat up.

  2. Mark, that sounds like a great way to use those clippings. I bought a bag for my mower to use the clippings in my regular compost but I did toss a bit on top of my “cardboard hole” to help hold some moisture in while everything rots. Of course, I don’t use anything toxic on my grass, except town water, LOL.

  3. I’m wondering, are there any reasons you shouldn’t use clippings from your organic vegetable plants. Or from houseplants?

    After food scraps/waste this is my greatest source of ‘green matter’. As some of my plants tend to be a bit prolific (for some reason my plants always try to invade new parts of my living room…).

    Mark, your way of composting grass clippings looks like a good way (would try it if I had a yard, and not a balcony 😉 ). However on environmental reasons I wouldn’t recommend using peat moss. As it can destroy (worst case) or alter the bog ecosystem. I would recommend using old potting soil that has given it’s best (don’t know if you’re doing that already). You’ll rejuvenate (at least partially) your peat moss with new nutrients.

    This year I’ve started using coco peat for my plants, and thus far I’ve been quite happy with it. You might try this as a substitute (mind you though, it is more expensive than peat moss. So I wouldn’t recommend using a new bag for composting).

    • AndreasDerKrieger
    • June 4, 2009

    I have tried grass clippings as well as compost in my indoor system. One drawback was bugs. The woodlice don’t bother me much, but the midges…whewee…Had to move the system outside.

    • Duff in VT
    • June 4, 2009

    My worms have developed a fondness for compost balls, from my compost tumbler. Partially composted matter that has formed clumps (I dump it on the ground and let “cool” for a few weeks and then feed it to the worms). If I freeze these balls, will it kill off any pests in them? I don’t want to bring unwanted bugs in the house !

    • Bentley
    • June 4, 2009

    MARK – thanks for sharing that. Sounds like a cool method.

    ————

    COLIN – the only thing I’d be careful with is the fact that some plants contain toxins in their leaves. If I was unsure about a certain plant, I would probably put it in a ‘regular’ compost heap and let it rot for awhile – this should breakdown the nasty stuff.

    • Bentley
    • June 4, 2009

    DUFF – freezing should help, but some of these critters probably have pretty resistant eggs and/or resting stages, so ya never know. I don’t think most of them would thrive in a typical indoor environment though.

  4. Bentley
    I get the pun!

    • Wendy
    • June 8, 2009

    Hey Bentley,

    Having a rough start with my worms. They arrived on time via USPS and my plastic bin was ready to receive them. I punch holes on all four sides pressed the lid shut and left them oustside under a shaded area with an extra lid loosely placed on top.

    Unfortunately, it rained (poured) that night and to my dismay about one third of my wormis are missing. (just by visual calculations).

    Although the worms were not on the ground and were covered, I found just a few on the outside which is how I confirmed the escape ( I am sure I lost alot). The holes on the side were approximately three inches in circumference, five holes on each side.

    The next time it rained, more worms escaped. I had to double layer and capture the escapees back into the bin.

    WHAT AM I DOING WRONG??? The holes are near the top of the lid not at the bottom. How can they escape? I have food inside.
    I need help

    Wendy
    please respond to my email too

  5. Hi Wendy,
    Escapees are somewhat normal. Usually it indicates that some condition, or perhaps many conditions are out of whack. you mentioned your bin was ready, what’s inside? Did you let it sit and ready itself for awhile? My first bin didn’t have escapees, but I did have many, many up from the bin, clinging to the lid and the lip around the top. You also mentioned that your holes were about three inches in circumference. Anything larger than about 1/4 is going to give you problems because if they are looking to get out, that’s big enough to insure they will. If they’re actually that big, consider going to the home store and go to the gutter section and look for some round vents (see http://www.wormiculture.com/images/vent.jpg for a picture) you could stick in the holes to allow ventilation but help prevent escapes. I’ve also used landscaping material simply duct-taped over large holes. Check to make sure your mix isn’t too wet. I use shredded or cut up small pieces of cardboard to suck up excess moisture. It’s not a problem that they hang out of the mixture once in awhile, but all of them out of the mixture indicates a larger problem.

    • Iker
    • June 9, 2009

    Hey, I’ve been reading the site for a while now, and I must say it has taught me almost everything I know about vermicomposting, and I’m a huge fan now, so kudos for that!

    Anyway, I found this absolutely easy to use C:N calculator for all us vermi-enthusiasts, I hope it helps you all!
    http://www.milkwood.net/content/view/47/30/

    Keep up the good work!

  6. WENDY – there are several things that stood out for me as I read your comment. 1) The worms were recently received and added to a new bin.
    2) The bin was put outside in wet weather
    3) Your holes are 3 inches in circumference

    When worms get shipped and then added to a completely new system, they are almost ALWAYS going to be at least a little restless – often they are very restless. Aside from all the handling and bumping around, their new home is almost always a very different environment than they are used to. Worms raised on a large scale (by worm farmers) are very typically fed livestock manure. They will certainly consume rotting food wastes (and other materials) but it can take them a little while to get used to it. Add to this the fact that many people starting a worm bin are beginners and it’s no wonder there can be trouble early on (don’t worry, you are definitely NOT alone).

    Keeping worms inside a worm bin inside a dry/bright home is not all that difficult (at least once the restless stage has passed), but if left out in a dark, warm, wet environment – and provided with an escape route, there is a good chance they’ll start to explore (ESPECIALLY if they’ve just been introduced to this new environment). Your holes are far too big – even if we are talking about circumference, 3″ is huge for a worm bin. I personally prefer 1/8″ diameter.

    Anyway, really sorry to hear of your troubles Wendy – although glad you at least have some worms left.
    Hope this has helped a little
    8)

  7. Al: those are the vents I use

    Iker: I LOVE that calculator. Thank you very much.

  8. I moved a compost heap yesterday, and the worms were nearly all to be found in the stinkiest, wettest, nastiest clumps of rotting grass. So I think that they’ll definitely appreciate a grass clippings diet!

    • wendy
    • June 13, 2009

    Bently, Al Wright,

    I’m going to make the adjustments you recommended.

    Any suggestions to help minimize or get rid of the nasty little flies and pill bugs inside of bin.

    Don’t know how the pill bugs get in. They crawl and not fly.

    With regards to out door vermicomposting, were worms placed directly into a compost pile or did you biild a structure on the ground to seperate and restrict worms from escaping while adding the food source on top?

    Thanks
    Wendy

  9. Wendy,
    I found an informative article regarding pill bugs in your bin. ( http://ccmg.ucdavis.edu/files/55651.pdf ) says that they like the same wet conditions as worms. As for flies, I first thought I had fruit flies, but these were slow and stupid and turned out to be Spaerocerid flies, aka “dung flies”. ( http://www.doyourownpestcontrol.com/sphaerocerid-fly.htm ) One way to at least reduce the populations of flies is to use a layer of mulch, such as shredded paper, coir or peat to keep the attraction level as low as possible. I often open up the tops of my bins on a sunny day and let the top most layer dry out as the flies don’t seem to be tunneling down very far.
    My bins are mainly wooden ammo cases and some plastic under bed size bins with 1/8″ holes all around and under for drainage. I have them all off the ground on the shadiest side of my house about 3 feet on platforms. This keeps them high enough so I’m not bent over to keep them and away from ants and other crawling things. I also sprayed the legs with bug killer to keep them away. Hope this helps.

  10. I have a big problem with bugs and bug larva with my compost all of a sudden! I put a pound of my feedstock in the freezer for 36 hours, when it thawed some of the larva were still alive. Not wanting to add bugs to my bin, I found out that these bugs won’t survive the MICROWAVE for 5 minutes!

    • Hey Al Wright,
    • June 19, 2009

    Do you place the “plastic” inside or outside the wooden ammo cases?
    I got a supply of wooden veggie boxes from the supermarket and I thought about lining the inside of the boxes before placing the worms

    How do you prevent too much rain from getting inside the bins?
    Its been pretty wet in northern jersey the month so I had a rough rain/flodding problem with my bins

    thanks for the info on bugs I will read up on it

    Yes I too try to keep outside invasions of the other kind from entering my bins

    I went to Whole Foods to get some “organic” bug spray on my legs

    Wendy

  11. Wendy, the plastic I was referring to was the other kind of bin. I have the wooden ammo boxes as well as some plastic bins with lids, see http://www.wormiculture.com/images/whitebin.jpg . They all have holes drilled on the sides, top and bottom, so even if it pours, the excess water drains out. No doubt, my bins are getting pretty wet lately and I have partially covered them to keep one end of them dryer so my worms have someplace drier to hang out. I just laid a plank across them to deflect some water. If you need to line the veggie bins, you could use almost anything as long as you allow for drainage. Again, that landscape fabric or weed barrier http://www.wormiculture.com/images/weedbarrier.jpg might work fine to allow for drainage and keep them inside. I imagine you could cut it long enough and fold it over the top to keep them in and bugs out. The funny thing is that when I dig down to check on them, there are more worms of all sizes in the soggy side than on the drier side so I guess they don’t mind being very wet. I do turn my bins about once a week to keep them well mixed and aerated.

    • wendy
    • June 22, 2009

    Hi Al,

    Thank you. I will change the interrior from plastic to landscape fabric. I really think this is an excellent idea.

    Hey Bently, Al, and friends,

    with regards to using aged manure from the farm, do you think I can add/use the manure I buy from the garden shop in lieu of…

    I’m thinking of experimenting a small amount, although I will not be able to compare the results with the aged stuff…….

    Wendy

    • tyra
    • December 2, 2013

    Love it

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