Question from Joe:
How many worms do I need for a 4′ x 5′ composting bin and 7 raised
beds that are 5′ x 17′ x 1′ deep?
In my mind there are two main schools of thought regarding the “proper” stocking of a vermicomposting system (we’ll talk about your raised beds in a minute).
1) The “x lb of worms per sq ft” approach – the idea here is that you stock a certain quantity of worms per square ft of your bin’s upper surface area. An example of this can be found in Mary Appelhof’s “Worms Eat My Garbage” – she recommends one pound of worms for every 4 sq ft of bin space. So a bin that’s 2×2 would be stocked with 1 lb of worms.
This is a solid approach (and likely the most commonly used/recommended), especially when you are ordering worms by the pound. Some of the potential “negatives” can include restless worms, worm mortality, and greater cost.
2) Add worm-rich material (from another system) and not worry about exact quantities – this has been my preferred approach for quite a few years. What I like about it is that you are allowing the worm population to expand naturally to an ideal level based on the resources available (this can happen quite quickly with a new bin) and you are also adding lots of great starter material/organisms to help the worms get settled into their new home.
This can require a bit more patience, and the wormy material may not be readily available (assuming you don’t already have another vermicomposting system up and running), but on the plus side it’s more of a “natural” approach with fewer headaches early on (assuming you can resist the urge to add a lot of food) and can result in the rapid development of a large, healthy worm population. This approach can also be less risky/costly for those fairly new to vermicomposting.
Getting back to your question, Joe…
Assuming you are looking for a specific quantity of worms, according to Mary’s calculation your 4×5 bin should take about 5 lb of Red Worms. If you are fairly new to vermicomposting, my recommendation would be to start with less than that – perhaps 2 or 3 lb. Just make sure you get the bin set up like a worm bin (not a regular compost bin) beforehand, and keep a close eye on the temperature. A bin that big can easily overheat.
As for the raised beds – if these are being set up in a typical raised bed manner (eg “Square Foot Gardening” type of approach), I wouldn’t recommend stocking them with composting worms at all. Remember, they are not soil worms so they won’t do well in a typical garden bed.
If you were planning to mix in a lot of well-aged farmyard manure (real farm/stable stuff – not store bought) into the bed it would likely support some Red Worms. You could also install a vermicomposting trench or “Worm Tower” in the beds, and then simply stock those with worms.
Hope this helps!