How to Prepare Worm Castings?

Stephen Andrews
08 Aug 2022

Worm castings are a superior soil amendment that can benefit all plants, including organically-grown marijuana. Worm castings manure aerates and improves the soil, nourishes the plants with valuable nutrients, and also protects from pests such as aphids and spider mites. It's also fairly easy to prepare this multi-purpose organic type of fertilizer.

Benefits of Worm Castings

Also known as vermicast, worm castings are an organic form of fertilizer produced from earthworms. Practically, we are talking about worm poo here. Worms eat through organic debris such as compost, and the waste they leave behind is a perfect soil enrichment. 

The benefits of worm casting manure are several:

  • Improved soil aeration and drainage.
  • Increase water retention in the soil.
  • Provide plants with essential nutrients.
  • It can be used in every garden.
  • It can be applied directly to plants without causing any harm.
  • It can be used as a top dressing, side dressing, or working into the soil.

How to Make Worm Castings Manure?

Preparing worm castings for your cannabis garden is very easy. All you need is worm bins or boxes, some newspaper strips and sand, some compost/organic kitchen waste, and worms! Timewise, it takes about 30 minutes per week to maintain the worm composting, while harvesting can be done every 2-3 months.

For bins/boxes, it's good to use shallow wooden containers no deeper than 10-12 inches (around 30 cm). The containers should also have drainage holes at the bottom. Avoid bins and containers that are deeper to ensure the compost stays odor-free. Smaller bins are also more practical to fit in spaces such as under the kitchen sink or a cupboard.

Preparing a worm casting box involves the following steps:

  1. Dress the bottom of the bin/container with moist newspaper strips and sand.
  2. Add compost, manure, or leaf litter and another layer of wet newspaper strips. 
  3. Add some worms and leftover foods such as fruit and vegetable peels or garden waste on another layer.

Once the box is prepared, let the worms do their thing. Harvesting the precious poop/garden fertilizer from your worm castings can be done every 2-3 months. 

The simplest method to harvest is "dump and sort": 

  1. Empty the contents of the worm container onto a sheet of plastic or newspaper.
  2. Collect the worms and add them to a fresh vermicompost bin, then use the leftover castings on your plants.

One more harvesting method:

  1. Move the worm castings to one side of the bin and add new bedding to the other side.
  2. Add fresh food above the new bedding and wait for the worm to migrate over in the next couple of weeks. 

Happy vermicomposting!

Stephen Andrews