How to Harvest Worm Castings

  • By: Sam Richards
  • Date: March 4, 2023
  • Time to read: 5 min.

One of the goals of worm composting is to harvest their poop, which is abundant with nutrients. Also called vermicompost, you can add the castings to your plants, and in turn, will help them grow. This is an organic fertilizer that is produced by earthworms. To use the castings, you need to remove them from the bin and transfer to where you want to use them.

This quick guide talks about the fundamentals of harvesting worm castings. We’ll also let you know when the right time is to do so and share some tips on how you can do it like a pro.

When to Harvest

Before talking about the specific methods of harvesting, let’s first discuss proper timing. This is important to ensure that you will have optimal yield. It takes around two to six months before you are ready to take the castings off the compost. Aside from this, there are also some tell-tale signs that the castings are ready for harvest, including those mentioned below:

  • It develops a deep and dark brown color. If it turns black, then it means that it is beyond finished, losing all its beneficial properties.
  • It has a uniform texture. Try to grab a portion of the casting and feel the texture in your hand to see if it is ready for harvest.
  • It is ready for harvest when worm reproduction slows. Worms have limits when it comes to their reproduction rate. When they reach this limit, it is time to harvest.

The Different Ways of Harvesting Worm Castings

Once you have determined that they are ready for harvest, it is now time to get your hands dirty. There is no single best way to do this. There are different methods, and you can choose which one is suitable for your preference.

Migration Method

The name itself should already give you an idea of how it works. The main idea is to let the worms get out of the bin by themselves. They will naturally follow their food source. So, all that you have to do is to avoid adding more food scraps when you are ready for harvest. This will encourage worm relocations, and they will leave castings that will be easier for you to harvest. This way, you will not need to separate the worms from the vermicast.

In a tray, move all the organic food scraps on the other end. If you are adding more scraps, put them on one end. This will encourage the worm to move on that side. Meanwhile, if you have multiple trays, there must be a way for the worms to move horizontally or vertically depending on where the food is. When they move, you can easily harvest the castings without separating them from the worm. This will make your life a lot easier.

Light Method

This method relies on photosensitivity to harvest castings. Because worms are naturally sensitive to light, they will move away from it and transfer somewhere it is darker. Being photophobic, worms will dig into a darker environment. This means that they will hide, leaving the castings free for you to remove.

To do this, gather the compost and put a light source on the top. You can also make a pyramid out of the compost and expose the top part to lighting. The worms will then dig deeper into the pyramid. When they are out, all that you have to do is to scoop the castings.

Dump Method

It is one of the simplest methods for harvesting worm casting. As the name implies, this requires dumping the compost. You will simply have to dump the contents of the compost in the garden, about half of the current size. When they are in a larger environment, worms will not gather in a specific area. This means that they will be soon moving out of the compost, leaving the castings free for you to harvest.

While this is a simple method, some people do not like how it loses half of the worms in the bin. The moment that you dump half of the compost, you are letting go of most of the worms, setting them free in the garden.

Screen Method

You will need a screen to do this harvesting method. The key to the success of this method is the use of the right screen. If the holes are too large, then everything will just fall through the bottom. On the other hand, when the holes are too small, then the castings will not fit through them.

To do this, add a screen on the top of the bin or in any other area where you are comfortable working. Grab a handful of the compost and position on the top of the screen. Spread the compost. The castings will push through, allowing you to separate them from the rest of the compost. You might need to repeat the procedure if there are still more castings that remain.

Handpicking Method

This is perhaps the simplest of all the harvesting methods on our list. You have to do it manually, which makes it quite tedious. Dig until the bottom of the bin and scoop a handful of the compost. Hand-pick the worms and put them back on the tray. The one on your hand, meanwhile, can now be dumped wherever you would like to use the castings. Make sure to handle the worms with caution. If you apply too much force, you will end up squishing them and they might die.


In sum, there are multiple ways for harvesting worm castings. There is no best method as it all boils down to personal preference. From handpicking to using a light source, consider our recommendations above. It is important that you time the harvest properly, making sure that the castings are ready to provide the nutrients they are supposed to impart on soil. Be gentle so that you won’t kill the worms while they are separated from their casting.

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