September 2010

Worm Bed Surface Area

Here’s a question from Al:

Love your site. Now to the meat…

You mentioned that “…surface area is
far more important than depth…”. And
thus bins are better than buckets.

Under optimal conditions, what would the
density of worms (E. fetida) be per square
foot of “bin top”? In other words, how
many worms, under ideal conditions, would
be feeding on a square foot of food?

Really appreciate your site. Thank you.


Hi Al,
This is an interesting topic of discussion for sure. Thanks for bringing it up.
You mentioned E. fetida (Red Worms) so I know you are referring specifically to them, but I DO want to emphasize (for other people’s benefit) that depth is a bit more important when raising European Nightcrawlers (E. hortensis). While I still wouldn’t recommend the use of buckets, in my experience (and based on what I’ve read) a deeper tub system or bed seems to work better than shallower tubs/trays and stacking systems.

Now, getting to your main question there. As per usual (with vermicomposting) there is no set-in-stone answer to that unfortunately – well ok, there is ONE answer that never seems to change: “it all depends!
Seriously though, it really does depend on a lot of different factors, and as such, worm densities from one system to the next can vary substantially. I’ve read reports of professionally managed systems reaching densities as high as 4 lb (or more) per sq ft, believe it or not! My guess is that the “optimal” density for a well looked after home system might be more along the lines of 1/2 lb – 1 lb per sq ft.

My question, though, has always revolved around depth – I’ve never seen mention of a standard depth used for these measurements. Obviously, all your worms aren’t just sitting on top of the bed in one big gob. You would need to collect everything from at least the top few inches, and even if there was a standard depth used, we’d also need to remember that Red Worms don’t always do what they are expected to do! I’ve seen lots and lots of worms hanging out down in wet mucky zones of plastic tub systems, for example.

If you are looking for a reasonable estimate for stocking density (i.e. the quantity of worms to add to a given system), I might suggest going with 1/4 lb – 1/2 lb per sq ft. So, if your bin measures 4ftx3ft, you might thinking about stocking it with 3 lb – 6 lb of worms. I tend to be a little on the conservative side though, so don’t take that as “gospel”. In all honesty, I prefer to let a worm population grow into a given system rather than trying to start with an “optimal” density. In my mind, it doesn’t make all that much sense to optimize the worm population when the system itself is not yet optimized (generally takes place over time).

Anyway – not sure if I really answered your question, Al! I’m hopeful we’ll see some input from others as well.

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Why Do Red Worms Love Brown Cardboard?

I recently received an interesting question from one of our regular readers, Dave P.
I didn’t actually plan to publish it (and my response) here, but Dave thought it might be valuable to get input from others (i.e. Bentley’s response was pretty lame! haha!). Joking aside, I think Dave is right about this being a good potential topic for discussion. Directly below Dave’s question, I’ve included my initial email response (with some minor edits), followed by some additional thoughts added when I put this blog post together.

Over the last few months two things have contrived to make me
ask “why do worms love plain brown cardboard”?

1. I have two 1M cubed compost bins. I recently emptied (bar a few
worms) one and started a new one. I had it about two feet deep with
fresh garden waste, a few buckets of kitchen waste.

2. I happened to have a few items delivered in plain brown card, as
per Amazon books? Nothing special, just brown card. Soak it in water,
pull it apart and leave it for the worms.

Result? My garden compost is magically turned into fantastic
brown/black ‘fertilizer’!

What is it about cardboard that makes them start chomping? An old
‘yellow pages’ book didn’t go down half so well. Yet there is no sign
of the plain card?

I’m mystified. I can’t see any food value in it? Roughage?

Hi Dave,
GREAT question, and something I myself have certainly wondered about over the years. Something I saw suggested once may hold the key. Some have suggested that it might be the glue used in this material that provides the food value – all those layers get stuck together somehow, and it’s probably somewhat similar to that paste we used to use in pre-school. Pretty innocuous stuff, but likely containing some nutrients (polysaccharides for the microbes? I dunno).
The worms seem to love using it as a habitat as well – worming their way down the channels.

Anyway – I guess I’m really not sure at all – but I do LOVE the stuff! If only it was a lot easier to shred it up!

Additional Thoughts

I managed to track down the source of the “cardboard glue” theory mentioned above. It appeared in a Worm Digest article called “Paper Pulp Alone as Redworm Feedstock?!” (Worm Digest, Iss. #22, p.16). Here is the exact quote:

Though the glues in corrugated cardboard are thought to supply a significant protein source, this has not been substantiated

The article also touches on the fact that high-carbon (and low nitrogen) materials like cardboard can be readily colonized by many species of fungi. Given the fact that most of use (who use cardboard as bedding), are also adding other “food” materials (typically with higher nitrogen content), it becomes a bit easier to see how the worms might find the cardboard as appealing as they do. It soaks up juices from the rotting food waste etc, and undoubtedly develops a pretty substantial microbial population as a result.

Anyway – just my 2 cents (with some assistance from Worm Digest).
Thanks for the cool question, Dave! Hopefully others will add some input as well.

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Mark’s Winter Cocoon Experiment

Hi everyone,
This summer I tried to copy Bentley’s trench garden only in a bucket. This is a watermelon plant I bought for $2.00. When I got it, the season was late for watermelon (which is why it was on sale). The plant only had two or three leaves on it and I did not expect much. I planted it in a five gallon bucket with ½ dirt and ½ manure.
I put ¼ of a pound of worms in the bucket so the worms would deploy the VC for me like the trench does.

As you can see, the plant flourished some but, late in the season and the extreme heat took its toll. I was going to dump all the contents in the compost bed when I discovered
cocoons in the soil. I then decided to add another ½ pound of worms to the bucket in the hopes of more cocoons being deployed. I intend to leave it out all winter to try the frozen cocoons test and the species survival test (the one about the worms laying many cocoons when their habitat is declining)

This photo shows the bucket up on boards to permit air to the holes I drilled in the bottom.

‘Mark from Kansas’ is an avid vermicomposter from…well…Kansas, and contributing author here at Red Worm Composting. When he is not tending to his OSCR worm bin, Mark also enjoys spending time with his wife Letty (who also doubles as his trusty vermicomposting assistant) and picking petunias (ok, Bentley just made that last bit up).

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Can Worm Cocoons Be Effectively Harvested?

I recently received a couple of similar questions from “Gail” and “Kevin”. This is a topic that a lot of people seem interested in.

When I try to separate my worms from the compost I cannot
remove all the eggs and then I give up and put the worms back. Do eggs
have to be sacrificed? It seems mean, but I want my compost!

I harvested my bins for the first time this week.
Do you have a better method for harvesting cocoons than picking them out one at a time.

Hi Gail/Kevin,
You have touched on one of the major dilemmas of vermicomposting, and something I’ve yet to see a really good solution for. As nice as it is to produce and use beautiful worm compost that we’ve made from “waste” materials, it’s not much fun to see all that “future worm composting potential” end up potentially lost.

I personally don’t worry about this issue as much as some, simply because I happen to have a very extensive network of worm composting beds closely associated with my gardens. As such, I know that any baby worms hatching out will end up finding a good “home” quite easily and quickly. I realize that not everyone has the desire, or even necessarily the ability to dig a big network of vermicomposting trenches (it can involve some serious labor), but something you MIGHT want to consider, assuming the compost is being used in your own garden, is a smaller pit-type system associated with each plant (or a small group of plants).

Just to give you an example of what I mean here – this year I planted a couple of small boysenberry bushes in a heavy-clay-soil garden I have not done much with (as compared to a lot of my other “vermi-gardens”, anyway). When I planted each of them, I started by digging a really big hole. Next I filled it most of the way with a coarse vermicompost material, containing lots of cocoons and even worms. Then – after planting the bush and adding more vermicompost – I added quite a lot of alpaca manure over top. Finally I covered everything with a thick layer of straw. You certainly wouldn’t need to use alpaca manure (or manure in general) though – food waste could work as well. It would have the added benefit of providing slow release moisture in addition to being a worm “food” source.

Getting back to the original topic

HOW you are creating your vermicompost will likely have an impact on the ease with which you are able to separate the cocoons. In a plastic enclosed type of system, generally you will end up with a pretty mucky material which will obviously make it really difficult to do any sort of separation (even from the worms, for that matter – but be sure to check out some of the different approaches mentioned in the Harvesting section on the HOT TOPICS page for ideas about how to do that).

Vermicomposts produced in a really well-aerated system, especially some sort of “flow-through” bin/bed, will tend to produce a nice, crumbly vermicompost that should be a lot easier to screen. Start with a bigger mesh size (say 1/4″) and work your way down (anyone out there tried 1/16″?? I’ve meaning to). It’s not likely that you can ever separate them so that you only end up with cocoons, but I suspect that you could end up with a mix that makes it a lot easier to remove them by hand.

Something else you might want to consider is attempting to get your cocoons to hatch out in the vermicompost before you start using it. In the case of wet vermicompost, it is always a good idea to give it some time to air dry in a well-ventilated tub, or even in a heavy duty cardboard box (as suggested in “Worms Eat My Garbage”) – this can be a good time to see if you can encourage hatching to take place, and just generally round up all the babies left in the material. To accomplish this, you might try putting some cantaloupe or melon pieces on top of the compost, and simply cover it with some burlap (newsprint etc). Over time you should start to see lots of little guys congregating under the food materials. By the time your compost is nice and dry, hopefully you will end up being able to scoop up most of your remaining wigglers quite easily before you start using the material.

Anyway – just some thoughts on my end. Will be interested to see what others have to say!

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Does Freezing Kill Fruit Flies?

A small bag ‘o’ rotten fruit scraps (containing fruit fly larvae and/or eggs) ready for freezing

Not too long ago, one of our regular readers, George, shared a really interesting (and surprising) tidbit of info about fruit flies. In a nutshell, he has found that these annoying pests seem to be able to survive freezing temperatures!

Given the fact that I recommend freezing fruit/veggie wastes as a means of ensuring the materials are free of viable fruit fly eggs/larvae, and have had (blind?) faith in this approach in general, I knew this was something I needed to look into!

SO, I’ve decided to start with a simple experiment, and then will expand from there as needed. Today I obtained several pieces of well-rotted fruit waste (an apple core, a piece of cantaloupe, and a piece of watermelon) from a section of outdoor worm bed has a lot of fruit flies associated with it. I feel pretty confident, then, that these materials will have at least some fruit fly eggs and larvae.

All I did with the pieces of fruit waste was put them in a small ziplock bag and toss them in my deep freezer. In a few days I will remove the bag and empty the contents into some sort of small container. I will let everything sit for a few days (indoors at room temperature) to see if any fruit flies appear. It will of course be important to make sure there is no chance of fruit flies getting in to the container. I do seem to have a few of them buzzing around in my kitchen and basement, so some extra precautions will certainly be warranted.

If I don’t see any fruit flies hatching out from the materials I will repeat the experiment, but will make absolutely sure there are fruit flies to begin with (by letting some fruit/veggie waste sit exposed in a small container outside until there are clouds of them in the container). If it does seem like fruit flies have hatched out from the frozen material, I will also repeat the experiment just to make sure.

Thanks, George, for the inspiration!
Should be interesting.

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Ants vs Black Soldier Fly

Ants attack Black Soldier Fly

Our good friend Larry Duke sent me an email the other day with an intriguing photo (above) attached. Me being me, I promptly asked Larry if he’d mind me sharing it, along with his brief explanation. Larry being Larry (haha), he happily obliged. Here’s what he had to say (about the photo):

Hey Bentley. Just wanted to post a picture of a newly hatched BSF – under attack by ants – I rescued! Ants serve a purpose. Just wish it wasn’t in my worm bins! When I picked it up, the ants would not let go until they got smashed. The Soldier fly survived. I’m not sure if he was stung by the ants. They may not be harmed by the sting. You got me on that one!

I can’t help but wonder if these fire ants attack the worms as well? (Larry – have you seen any evidence of this?)
I myself haven’t found any evidence of ants actually attacking worms in any of my beds, and there are literally ant nests in the middle of a couple of my beds (and still plenty of worms in the general vicinity) – but our ants likely aren’t nearly as aggressive as fire ants.

Anyway, thanks yet again to Larry for sharing!

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African Nightcrawlers Chow Down!

My worm-friend, Andrew, recently sent me a link to a cool video he made. It features his African Nightcrawlers (Eudrilus eugeniae) munching away on some waste materials. Not sure what sort of camera he used, but it’s wild how close up (and clear) it is!

As long as you keep these worms warm (ideally above 20C/68F), they are apparently pretty voracious feeders! Seeing the mouths on the ones in the video, this doesn’t surprise me at all!

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