Apr 152010
Take great care and caution when separating worms from their castings.

The best way to harvest is to entice the worms out of their castings and into fresh bedding and food.

“Harvesting” worm castings means separating worm poop (called castings) from worms.  The goal is to use the worm composting castings to feed your garden, while putting the worms back to work in fresh bedding.  After you set up your worm bin, it should be ready for harvest in about 4 months.

Attempts to Automate Harvesting

I’ve seen two homemade machines built to separate worms from their castings.  One was a slanted wire mesh tube about 4 feet long that vibrated jerkily.  The other was a 3-foot cylinder of hardware cloth that turned on a spit.  The intention behind these contraptions was for the worms to remain in the sifter while castings fell through.  In both machines, lots of worms were frantically clinging to the mesh while it seemed that just as many fell through, dropping 2 to 3 feet to the earth below.

I was raised on the Golden Rule, so I have to ask, “If our roles in life were reversed, would I want the worm to do this to me?”  The answer is an emphatic, “No.”

Attempts at Manual Harvesting

Some people harvest castings by digging through them and removing the worms one at a time.  This is stressful for the worms because, physically, being touched by human hands dries their skin.  Psychologically, it’s just plain scary for them.

Letting Mother Nature Do Her Thing

The best way to harvest is to entice the worms out of their castings and into fresh bedding and food.  As the worm habitat becomes saturated with castings, it is less healthy for them.  They naturally start looking for a better place to live.  So, give them one!

After several months, there will be more castings than bedding in your bin which indicates harvesting time is near. Push all the contents of the bin to one side, so they are taking up only half of the bin.  Put fresh bedding in the other half.  At feeding time, place food only in the new bedding.  When the old conditions are no longer beneficial, worms will move into the new bedding.  When there are no more worms in the old castings, you can remove them and add fresh bedding to that side of the bin.

Benefits of Letting the Worms Decide

The beauty of this natural method is that you don’t have to decide when it’s time to harvest.  The worms will decide for you.  If you try to harvest castings while they still provide a beneficial environment, the worms just won’t move to the new bedding.  It won’t hurt them, but they won’t migrate yet.  You don’t need to do anything, leave the new bedding there.  They’ll move when they are good and ready, and not before.

The second benefit is that it takes the least amount of your time.  You would have to provide fresh bedding and food anyway.  You can spend quality time with your kids instead of digging through worm poop.

Mary Tynes, Master Composter, www.mastercomposter.com

Image Credit: http://www.flickr.com/photos/jhirsch/2591401778/

  8 Responses to “Harvesting Worm Castings”

  1. You reinforced what I already thought. It is indeed tedious to pick the poor guys out one by one (although it’s a good guage of how the worm family is doing!) Love my worms and love their poop. I always try to do what is best for them, because they are so helpful to me. Happy worming to all.

  2. i agree with your seperation methods. I saw a few you-tube videos, and was a little stunned!
    I cant find info regarding properly storing the castings (after harvest). I live in an apartment and have a 5 gal bucket of pure black casting without worms. I know there are lots of other benificial organisms remaining. I live in Canada and was thinking of leaving them on my balcony at cold winter temps…please help me!!

  3. Great information. Just what I was looking for.

  4. I have a worm factory 360 and there seem to be LOTS of worms still left in the lower tray. They upper bins have plenty of new bedding, and food scraps, I’ve left the bottom tray alone now for about 4 months, and I still have quite a lot of worms there. Any ideas for harvesting that tray?

  5. Are there any food scraps and recognizable stuff left in that lower tray? If nothing significant, take out the tray, expose it to some bright light and the worms will crawl to the bottom of the tray. Delicately scrape out the top castings and do this a few times until there are just a wee bit o’ castings in the bottom and the wormies of course. dump this all into a top, active tray.

    Sometimes this happens, it has a lot to do with seasonality, temperature and moisture.

  6. […] they may not provide a complete fertilizer for all plants, worm castings are powerfully rich in nutrients.  A home worm composting bin will produce a small quantity of […]

  7. […] it is time to harvest.  This is especially true if the population seems to be decreasing.  See Harvesting Worm Castings for […]

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