How to Harvest Worm Castings


Today’s post is part 1 of 2 in learning what to do with this “black gold.” In this post I’ll share how to harvest worm castings. In the next installment I’ll share how to use worm castings.

It seems like forever ago since I last talked about compost worms without giving them away. ;) I‘ve been long overdue to curl up on the couch (well, actually my desk chair), a latte within reach, and tap away on my keyboard about these amazing little creatures.

If you’re a worm farm newbie maybe you’ve entertained a thought something like this:

“I have a large container in my kitchen FULL of worms and worm pooh. I’ve been TOLD this is a good thing. Of course it is. Why would a container full of manure next to my small children and food prepping area NOT be good?! What have I gotten myself into?”

WHAT is worm castings harvesting?

The whole point of keeping a compost worm bin is to end up with worm castings (or manure) and composted organic matter to use in your garden. While it does, indeed, take longer to get a lot of manure from worms as opposed to large homestead critters, I can think of at least 14 reasons to have compost worms instead of homestead critters.

Harvesting worm castings is the act of separating the worms from the composted bedding and worm castings.

WHEN is the worm bin ready to harvest?

When your worm bin bedding – try saying that 10 times – turns from wet, fluffy, shredded newspaper and cardboard to a slightly slimy and muddy consistency to a nice crumbly dirt-like product you’re ready to harvest the goodies.

As far as how long it takes to get to this point, it depends. I’ve heard people give estimations, but it really depends on the number of worms, the amount of scraps, and how much bedding they have to break down. But, a rule of thumb is always nice to have. I’ve read it takes around three months. (My bin took longer.) Again, it depends on a number of factors.

HOW do you harvest worm castings?

Before harvesting the castings you’ll need to have another bin (DIY compost worm bin) ready to place the worms in once you’ve harvested the castings.

Think of it like this. If you’re a mother, you had a baby shower and had the nursery prepared BEFORE you brought your baby home from the hospital (or homebirth, etc.). Or, if you’re a mother of canine babies, like me, you probably purchased a dog bed, dog food, dog bowl, and a couple of toys BEFORE you brought the puppy home. It’s sort of the same with worms, except it’s … nothing like these examples at all, but sort of is. :)

There are a few ways to harvest castings. Two common ways are as follows:

  1. Using light to move the worms to the bottom of a pile, and
  2. Feeding the worms in one location of the bin.

Basically, you’re trying to get all the worms to gather together so that you don’t have to pick them out one by one.

A word of caution: When using the light method, do NOT place the worms where they are or will end up in direct sunlight. Direct sunlight will dry out, cook, and kill the worms. Remember, worms need skin moisture to breathe; their skin is ultra sensitive to light; and the intense heat from direct sunlight isn’t pleasant for anyone. Indoor lighting or ambient lighting of an outdoor shade will do just fine.

I’ve explained the light process in the below photos. The feeding process would be very similar.

I took a few handfuls of my worm bin contents to demonstrate the harvest process. I didn’t want you to think you’d wait months for only what is seen in the photos. ;)


No matter how you harvest the castings, you’re going to accidentally toss out some small worms and cocoons. It’s inevitable. Some of the worms are so tiny, it just can’t be helped.

Here’s the link to the Compost Worms 101 series, in case you’ve missed any of the installments.

This was shared on the following blog hops or link-ups:
‘Encourage One Another’ Wednesday Link-Up
From the Farm Blog Hop
Homestead Barn Hop
Simple Lives Thursday
Simple Living Wednesday Link-Up

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