This post was graciously written by my friend Jo, from the blog Homestead Chronicles. I want to welcome Jo to this space and thank her for coming to share her knowledge with us today. Welcome, Jo!
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. Yes, I know but try to get passed the yuck factor for a minute because I am going to explain how not to have to deal with the yuck factor at all! Yes, there is a way!
Before I go any further, though, I want to make it clear that I am by NO MEANS a vermicomposting or worm expert.
In fact, when I bought my worms, I simply had to trust that the retailer was indeed selling me red wigglers. To me, a worm is a worm. But now that I have a full year under my belt, I can give you the basics – a plain English overview of vermicomposting to help you get your head around it. As we go along I will give you resources where you can get more in-depth information. But first, let’s discuss, “Why vermicompost at all?” (If you already know, you can skip the next section.)
Why Vermicompost at All?
Worm castings used as fertilizer provides all sorts nutrients and trace minerals (such as nitrogen, phosphorus, and potassium) and 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 which means that they are in a form that plants can metabolize on a cellular level … which is WHY it works. This is mostly because of all the microbial life (germs) at work. Additionally, 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.
So castings not only provide an excellent source of nutrient-rich organic fertilizer but it also serves as a soil conditioner. Oh, and one last thing worth note: studies indicate that worm castings (as compared to regular compost that has not been digested by worms) contain significantly fewer contaminants and more nutrients than just plain ol’ composted organic matter that has never seen a worm. So while your regular compost is great, vermicompost is even better. More bang for the buck! The best part is that this method is completely chemical-free, and if not having unnecessary chemicals on your food or hidden in the cells of your food is important to you, then that matters.
So what is the downside? Castings are neither cheap to buy nor fun to handle but I have a way around BOTH problems!
If you just do not want to do your own vermicomposting and rather just buy it, you can. But a 15 pound bag of worm castings can run anywhere from $18 to $35 USD and that does not go very far. You may thinking, “That is pricy, but if I do it myself, then I have manage the worm poop, right?” Well, not necessarily – not if you use the tower method. So let’s get into the methods!
Housing Your Worms
Assuming you are running a small (home) worm farm operation (and not planning to get rich selling worm poop), there are two basic ways to raise compost worms for their castings. One is the bin method and one is the tower method and done properly, they both work quite well. This is really the biggest decision you need to make so let’s briefly describe both.
The Bin Method
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. Be sure to explore numerous approaches to bin construction before settling on one because each one has its own unique set of pros and cons.
- 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.
The Tower Method
My preferred method is the worm tower. It is quick & simple, just needs set in place, and never requires cleaning or “poop sorting.”
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.
I have deep affinity for the tower method mostly because a) I am lazy that way and b) not really excited about bin maintenance and poop management and c) I trust nature to do its job probably better than I can. But you may not agree, so let’s look carefully at the pros & cons:
Method Pros Cons
How to Apply the Castings
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. For a great method on how to make compost tea from any manure based compost, visit How To Brew Chicken Poop (or Horse Manure) Fertilizer Tea for your Garden at Fresh Eggs Daily. This method works just fine for worm castings, too!
- 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 Worms and Where to 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 and because they eat decomposing vegetable matter. But you can also use other species like the Dilong (Lumbricus rubellus), European nightcrawlers (Eisenia hortensis), or 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 (although, I am not sure what is). Compost 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.
Yes, it was a bit over my head too! TMI! Keep it simple and get red wigglers.M/h2.
is important here is to choose a composting worm species that is
a) suited your to climate b) adapts well to living & procreating in the confined space of a worm bin (assuming bins are your method of choice) and c) 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 an unsubstantiated rumor/hypothesis that says some red wigglers can be invasive in the northern US.
While I HOPE that my worm tower is environmentally responsible, I have no proof that it is and no proof that it isn’t. I installed my worm tower before I found out about this, so if some folks are right … well, it is too late now. Point is, we have no conclusive evidence one way or the other. Check this article for details and just be aware: Do Composting Worms Pose a Threat As An Invasive Species.
Okay, now you have an overview of why to vermicompost,
the basic (home) methods and their pros & cons, what kind of worms to buy & where, and how to make use of the gardener’s black gold … castings. Let me know if you have any questions. I will help as best as I can.