Known as vermicomposting, raising worms specifically for the purpose of harvesting the castings to use as garden fertilizer is both an organic and effective method for giving your vegetables the nutrients they need to thrive. Castings are worm poop – waste – what worms “cast off” as excrement, and to a gardener, it is pure black gold.
There is a learning curve when it comes to beginning a vermicomposting project. When I bought my first worms, I simply had to trust that the retailer was indeed selling me red wigglers. To me, a worm is a worm. However, I am going to share with you all that I learned along the way. But first:
Why vermicomposting in the first place?
Worm casting used as fertilizer provides all sorts nutrients and trace minerals (such as nitrogen, phosphorus, and potassium). It rejuvenates and conditions tired soil to better hold those nutrients in place (so they do not wash away with watering). The nutrients they provide are naturally water-soluble, meaning that they are in a form that plants can metabolize on a cellular level … which is WHY it works.
This is because of all the microbial life (germs) at work. Worm castings also contain that slimy stuff (the mucus that worms produce). That slime helps to hold those nutrients in place in the soil during watering so that it better retains the nutrients and moisture longer. It is just nature’s way.
Castings not only provide an excellent source of nutrient-rich organic fertilizer but it also serves as a soil conditioner. Some studies indicate that worm castings contain significantly fewer contaminants and more nutrients than just regular composted organic matter that has never seen a worm. So while your regular compost is great, vermicompost is even better. The best part is that vermicomposting is completely chemical-free, and easy to do.
Of course, there are downsides to vermicomposting.
- Castings are not cheap to buy. A 15 lb. bag can cost as much as $35, and that doesn’t go very far.
- The castings are not fun to handle.
I have a way around BOTH problems! There are a couple methods that will allow you to grow your own castings cheaply, without having to handle the castings yourself.
Housing Your Vermicomposting Worms
Assuming you are running a small (home) worm farm operation there are two basic ways to raise compost worms for their castings. One is the bin method and one is the tower method. If done properly, they both work quite well. This is really the first decision you need to make when starting your vermicomposting project.
The bin method of vermicomposting.
You can build a bin, buy it, create it from repurposed materials, or just wing it. Just be sure there are adequate air & drainage holes. The bin method can also make a great project for teaching vermicomposting for kids.
Consider different approaches to bin construction before settling on one because each one has its own unique set of pros and cons. Other things to keep in mind when starting your vermicomposting project:
- Don’t use metal (retains too much heat, can rust, and can leach heavy metals into the otherwise healthy compost and castings).
- If you use wood, avoid cedars and redwood because they have resinous oils that can be harmful to your worms or to your food. Choose a wood that will hold up well to very moist conditions without rotting but that has not been treated with hazardous chemicals.
- Large plastic tote bins or buckets are a pretty safe bet.
Photo courtesy of Kathie Lapcevic of Homespun Seasonal Living
You can find detailed instructions in this post from Common Sense Homesteading: Getting Started Vermicomposting.
The Tower Method of vermicomposting
This method is quick and simple. Once set into place, it never needs cleaning or casting removal.
- Put a bunch of holes in a PVC pipe.
- Plant it permanently and vertically in a deep hole in the middle of the garden.
- Backfill it.
- Place in some worms.
- Start filling with kitchen scrapes a couple times a week.
You can find detailed instructions in this post from Homestead Chronicles: Raising Worms For Castings Part 2.
There are pros and cons to each method, and you can decide what will work best for you and your homestead. Vermicomposting is not an “all or nothing” project. You can go back and forth between methods, or have both going at the same time. Some pros and cons to each method:
Now that you have your vermicomposting going, and your worms are making castings, how do you apply them?
If you are using the tower method, the worms spread their castings for you – all on their own (so no yuck factor). But with the bin method, you will have to harvest and then apply the castings to the garden yourself. There are a several ways you can do it.
- Mix the solid castings directly into the soil just like you would regular compost. That slimy mucus I spoke of earlier creates a time release fertilizer which cannot burn plants so this method is safe for your plants.
- Make compost tea and water your plants with it.
- Diluted with 50% water, you can turn it into a spray for use right on the plant’s foliage but be careful. This method is sans the slime and could be too strong. Such over-fertilization can cause nitrogen burn.
What kind of vermicomposting worms do I use and where do I find them?
Note that these worms are neither the kind that crawls up on the sidewalk after a storm nor are they the kind that anglers typically use as bait (although you can). For vermicomposting, most folks go with red wigglers (Eisenia fetida or Eisenia andrei) because they adapt best to the shallow depths of the typical worm bin, while comsuming decomposing vegetable matter. Other species lto consider are:
- Dilong (Lumbricus rubellus)
- European nightcrawlers (Eisenia hortensis)
- African nightcrawlers (Eudrilus eugeniae).
We do not recommend the Canadian nightcrawlers (Lumbricus terrestris) or the common earthworm as they like to go much deeper and decaying kitchen scraps may not be their preferred diet. Vermicomposting worms are drawn to compost specifically. All others, not so much.
In scientific terms, Wikipedia puts it like this:
Composting worms which are detritivorous (eaters of trash), such as the red wiggler Eisenia fetidae, are epigeic (surface dwellers) together with symbiotic associated microbes are the ideal vectors for decomposing food waste. Common earthworms such as Lumbricus terrestris are anecic (deep burrowing) species and hence unsuitable for use in a closed system.
Keep it simple and get red wigglers for your vermicomposting. It’s important here is to choose a composting worm species that is
- suited your to climate
- adapts well to living & procreating in the confined space of a worm bin (assuming bins are your method of choice)
- is happy to eat rotting kitchen scrapes (or other decomposing plant matter – you know, the stuff from your garden that you won’t eat).
You can find such worms online, at garden centers, or bait stores or you can collect them yourself from existing compost piles (which tend to attract the right kinds of worms in the first place).
All that said, there is a rumor/hypothesis that says some red wigglers can be invasive in the northern US. Check this article for details: Do Composting Worms Pose a Threat As An Invasive Species.
Now you know why to vermicompost, the basic (home) methods and their pros & cons. You also know what kind of worms to buy & where, and how to make use of the gardener’s black gold … castings. How will you start your vermicomposting project?
Heather’s homesteading journey started in 2006, with baby steps: first, she got a few raised beds, some chickens, and rabbits. Over the years, she amassed a wealth of homesteading knowledge, knowledge that you can find in the articles of this blog.