Plastia In-Ground Worm Composter

The Plastia In-Ground Worm Composter

Download the In-Ground Composter Set-Up Instructions (pdf file).

New PC Product Feature

Plastia in-ground vermicomposter

We’re pleased to announce the launch of a brand new product in the PC line-up! The “In-Ground Worm Composter” - produced by award-winning composting and gardening system innovators, Plastia Products - is designed to help you enjoy the benefits of vermicomposting directly in your gardens.

In this article, we’ll introduce you to the topic of in-ground vermicomposting, and show you how you can put the In-Ground Worm Composter system to good use.

In-Ground Vermicomposting 101

It’s no secret that earthworms are powerful agents of fertility in garden soils. It was Charles Darwin who first sang their praises when he published his book, “The Formation of Vegetable Mould Through the Action of Worms” in the late 1800’s. The list of earthworm evangelists has only continued to grow since then.

It’s also no secret - at least not among seasoned composters and gardeners - that certain varieties of earthworms are especially well-suited for turning large quantities of organic matter into rich worm castings quite quickly. These are the varieties we collectively refer to as “composting worms” - with the Red Wiggler Worm (Eisenia sp) being the best known, and likely most versatile, among them.

But there is a bit of a problem…a disconnect of sorts…

…one key detail that seems to have fallen through the cracks over the years.

Composting worms are not designed to thrive in soils

They’re what’s known as “epigeic” earthworms, which is to say they live in the very uppermost layers of soil or - more typically - in rich deposits of organic matter partially integrated with, or sitting on top of, the soil. 

Contrary to what some worm suppliers will have you believe, simply dumping a batch of composting worms into your garden is not going to help you boost your soil fertility in any sort of appreciable way!

This, of course, is where in-ground vermicomposting systems come to the rescue. We get to enjoy all the benefits of worm composting exactly where we ultimately want them - in our soil!

The “big idea” here is that we are providing our composting worms with an environment they can thrive (do what they do best) in - but also a means for our garden soils, and of course our plants, to directly benefit from this activity.

What Makes In-Ground Vermicomposting So Special?

We’ve already hit on the key benefit of integrating worm composting systems into our gardens - this idea of harnessing the talents of composting worms in a soil environment for the direct benefit of our plants. This means that our epigeic, wiggling friends have the habitat they need to succeed - and in turn, they will be able to pump out the beneficial products that are going to make our plants rejoice.

Beyond this, there are some other great perks associated with in-ground vermicomposting:

  • Much Simpler Process - Usually, we need to set up a worm bin, wait several months for enough castings to get deposited, dedicate some time and effort to harvesting those castings, and then (finally) put the material to good use in our gardens. With (integrated) in-ground systems, we simply set up the vermicomposting system right in the soil and mostly just let nature do the rest.

  • Fewer Hassles - Setting up indoor worm bins is a fantastic, space-saving way to compost kitchen scraps indoors all year long, but it’s not without its hassles and frustrations. Not everyone wants to have a hungry horde or Red Wigglers munching away on organic wastes inside their home…let alone all the other organisms that can come along for the ride. Outdoor vermicomposting systems can help us avoid this - but in many cases, we can end up faced with other challenges. This is where our next point comes in…

  • Protection for the Worms - The earth itself serves as the ultimate protection for our composting worms. You can think of it as the ultimate cooling and warming system. During hot weather, it’s usually cooler down below the soil surface. During cold weather the opposite is true. In both cases, the worms get to enjoy a much more moderate environment. Compared to above-ground systems, you will also see much better moisture-retention in these subterranean habitats.
  • Getting Started with the Plastia In-Ground Worm Composter


    The Plastia In-Ground Worm Composter offers the necessary size required to establish a composting worm habitat, yet is compact enough not to take over your gardening space!

    The unit is 26.7 cm across at its widest point and 47.6 cm long, with a volume of 12 litres.

    Plastia in-ground vermicomposter

    In-Ground Worm Composter Set-Up

    1) Assembling The Unit - This is a very simple process of snapping together the top and bottom pieces (the lid can remain off for now).

    Plastia in-ground vermicomposter

    2) Choosing The Best Location - As with any outdoor composter, proper site selection is a very important part of the process. We recommend using these units in garden beds where you plan to grow some plants (or already have some growing). For example, raised bed gardens earmarked for growing vegetables or herbs are a perfect choice. NOTE: It is best to install these composters early in the season, so as to avoid disturbing plant roots. It’s also important that your location remain easily accessible throughout the growing season.

    Plastia in-ground vermicomposter

    3) Digging Your Hole - We want the composter fully buried up to the widest part of the upper section, with a little extra room in the bottom for adding additional bedding (discussed next). A hole that’s 20-25 cm wide and 45-50 cm deep should work well. 

    4) Bottom Bedding - We recommend adding a small amount of bedding, such as shredded cardboard or hemp tow down in the bottom of your hole. This will help to catch any nutrient-rich liquids dripping down from above, while also giving the worms an additional safe zone outside the bin where they can gather during hotter (or colder) periods. 

    5) False Bottom - Create a similar bedding layer - ideally with shredded cardboard - down in the bottom of the composter. This should occupy no more than 1/4 of the total volume. Once again, this helps to ensure that nutrient-rich liquids aren’t just draining away into the soil. Over time this bedding will become an excellent food source for your worms. 

    6) Food & Living Material - Next, add some chopped up fruit and/or veggie scraps, such as leafy greens, banana peels, melon rinds or apple cores. If you have any living materials (LMs), such as old horse manure, rotten leaves or compost from another system - this is a great spot to add some of this as well. The LMs help to inoculate the system with beneficial microbes (and other helpful organisms), and to make the environment feel more like “home” for the worms.

    7) More Food & Habitat Materials - Add another thin layer of bedding (eg shredded cardboard, hemp tow or coco coir), and another thin layer of kitchen scraps / living material. This should bring you about 3/4 the way up. 

    NOTE: Small amounts of pH Buffer Grit or BioChar can be sprinkled in during the set-up process if you happen to have them, but this is not mandatory. 

    8) Watering -  Use a watering can to thoroughly wet down the contents of your in-ground composter. Thanks to the excellent drainage, we don’t need to worry about over-watering.

    Red Wiggler composting worms

    9) Adding Your Worms - As always, our number one recommended worm species is the Red Wiggler Worms (Eisenia fetida/andrei) since they are so easy to work with, and are well-adapted for a wide range of conditions. With a system this size, we suggest using no more than ¼ lb of worms. If you happen to have some other worm composting systems up and running, an alternate (and highly effective) stocking approach simply involves transferring over some worm-rich material. In this (latter) case, you may want to leave a little extra room since there will likely be a larger volume of habitat material that comes with the worms (NOTE: this is a highly valuable form of living material).

    9) Cover Bedding - Top up your system with a thick layer of dry cover bedding, such as shredded cardboard or hemp tow then put on the lid. This extra bedding helps with moisture retention, but also ensures that you will always have a starting layer of bedding as your base when you next add new deposits (something we’ll look at in the next section).

    Ongoing Maintenance

    These types of in-ground vermicomposting systems can be fairly low-maintenance compared to some worm bins, but there are definitely still some important considerations and ongoing activities you’ll need to be aware of.

    Feeding -

    As the level in the system continues to go down, you should periodically add more kitchen scraps and habitat materials to keep the system humming along nicely. Initially, you may actually be surprised by just how quickly the overall  level of material decreases. Keep in mind that some initial settling of materials - especially as the worms get more active - can play an important role in this. During the first week or two of operation, it will likely be a good idea to top everything up with an additional layer of kitchen scraps (and LMs if you have some) over top of the original “cover bedding”, along with a new cover bedding layer over top of that (food etc deposit). You can then repeat this basic process as needed.

    NOTE: While we would never recommend going too crazy with your food deposits in any worm composting system, the good news is that “overfeeding” in your Plastia In-Ground Worm Composter is less likely than in a more typical home-scale worm bin. Since the worms can move in and out of the system (that safe zone we set up in the bottom of the hole gives them a good place to hang out), it is far less likely that they will end up being harmed by less-than-favourable conditions in the composter. All this is to say that you can likely be a little more regular with your feedings than you would with a worm bin.

    Watering -

    As touched on earlier, in-ground systems can be very effective for moisture-retention in comparison to other outdoor options. But the one key difference from a regular worm bin that we really need to keep in mind is the powerful moisture-sucking ability of plant roots. Assuming you are using your in-ground worm composter(s) in active gardens (highly recommended), as the season progresses, it will be more likely that a lot of moisture is getting siphoned off by nearby plants - especially during hot, dry stretches. Be sure to keep an eye on moisture levels, especially later in the season, and don’t be shy about giving the system a good soaking on a regular basis!

    Refreshing and/or Resetting -

    Even with your plants making their regular withdrawals from these systems, like any worm composting system, we’re likely going to start to notice an accumulation of rich worm castings further down. How you deal with this is up to you.

    Option #1 - The Low-Maintenance Approach - If you aren’t overly concerned about conserving your worm population (or you have other nearby systems they can move to on their own), there is nothing wrong with simply leaving things as-is, and letting your system operate with little to no intervention from you during the growing season.

    Option #2 - “Refreshing” the System - If, on the other hand, you want to maximize the longevity of your in-ground system, a good approach is to refresh your habitat periodically during the growing season. The best way to do this is to remove excess castings as they start to build up in the composter. This is the darker, earthy-smelling (and looking), rich stuff that accumulates further down in the bin. You can remove modest amounts any time you add some new food/bedding deposits (good idea to wait at least a month before starting this process), and add the removed material directly to your garden - preferably close to where the unit is installed. Don’t worry about any worms that end up in your garden - they will easily find their way back to the composter.

    Option #3 - The Full Reset - In some cases, what you will find is that nearby plant roots start to wreak havoc on your in-ground system. This is a “good thing” for the plants, since it means they are really taking advantage of this ample resource you are providing them with, but it is almost always not a “good thing” for the worms, since the roots can choke out their habitat, making it difficult to move around, and it almost always results in a significant reduction in moisture content as well. If you system is close to some greedy crop plants (various cucurbits are common examples), you may need to do some sort of full reset part way through the season. In this case, we recommend doing what you can to lure your remaining worm population up into some rich food materials - eg. horse manure and/or your usual kitchen scraps, and then separate the worms out from the system altogether. The root-infested contents can then simply get dumped into a backyard composter and the set-up process started over again.

    End of Season Maintenance -

    Once your gardening season is over, in most locations it will make good sense to completely empty out your in-ground worm composter, and (hopefully) put the remaining population of composting worms to good use. If you have a more typical backyard composting system up and running, this can be a simple matter of dumping the contents into that. If there are still a lot of composting worms in the system, and you have an interest in continuing your efforts indoors, this can also be a great opportunity to use the worm-rich material to start up a new system.

    Set Up a Garden Fleet for Best Results!

    We encourage you to think of your In-Ground Worm Composters as all-natural, garden-fertility stations. Whether you decide to use more than one of these Plastia units, or you want to explore DIY options (something we’ll look at in an upcoming article), having a collection of in-ground vermicomposting systems going at once can definitely offer plenty of benefits.

    We hope you’ve found this article interesting, and are feeling at least a little inspired to start heading down the “in-ground vermicomposting” path. One thing is for sure - when you combine the amazing talents of composting worms with a more typical gardening environment, some pretty magical things can happen!

    Download the In-Ground Composter Set-Up Instructions (pdf file).

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