How to harvest worm castings.

When and how to harvest worm castings is one of the first questions aspiring worm farmers usually ask me when they 

purchase a worm farm from me. This is not surprising because worm castings are surly one of the greatest benefits we can derive from worm composting. Being one of nature’s best organic fertilizers and soil conditioners many are keen to put worm castings into action in their gardens.

Many ways are leading to Rome and there are as well several ways you can harvest worm castings. Below I will show you the probably easiest way to harvest worm castings from a multiple tier worm farm.

No matter if you are working with a 3 tier or 5 tier worm farm, the process of separating the worm castings from the worms and the food is basically the same.

If you have a Single worm bin please follow the link at the bottom of this page to our worm castings page for harvesting instructions.

But lets get back to the “multiple tier worm bins”

A 3 tier worm bin starts off with the worms, bedding and food in the second or middle bin.

The top bin will be empty and the bottom bin will be the place where the excess liquid will be collected before it’s drained off.

3 tier worm farm with empty top bin!3 tier worm farm with empty top bin!

Regularly add food to the middle bin of your worm farm right on top of the worm bedding.

The worms will feed on the organic materials you add to the worm bin, digest them and deposit them on top of their bedding as worm poop or worm castings.

A 3 tier worm farm with the top bin about half filled up.A 3 tier worm farm with the top bin about half filled up.

Repeat this cycle till the middle bin will be full to the top. Then start adding food to the top bin.

Compost worms are top feeders and will always follow the food supply upwards. So with time more and more worms will migrate into the top bin. You can assist this migration by always adding a handful of bedding and worms from the middle bin to the top bin when you are adding food for the worms.



When your top bin is more than half full most of your compost worms should have left the middle bin.

How to harvest worm castings

Now it will be time to harvest the worm castings from your middle bin. At this stage there should be no food left in the middle bin. To remove the remaining worms from the bin add a thin layer of food to it about 3 days before you want to harvest the castings.

On the day you want to harvest, remove the remaining food plus the top 5 cm / 2 inches of worm castings beneath the food from the middle bin. This way you will move the remaining worms from the middle bin and add them to the top worm bin.

The worm farm after the harvest of worm castings.The worm farm after the harvest of worm castings.

Now you can harvest the pure worm castings from your middle bin. Drop the bin that is holding the food and worms to the middle of your 3 tier worm farm and place the 

empty bin on top. Depending on the size of your worm bins and the amount of worms they hold you should be able to harvest fresh worm castings every 6 to 8 month this way!

Keep it up and Happy Worming!


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