DIY Vermicomposting III: Harvesting the Poop

Harvesting worm castings can provide nutritious, organic material for your garden. I harvest worm castings approximately every 90 days and can yield 1-2 quarts of vermicompost. Photo: Patricia Vollmer.
Harvesting worm castings can provide nutritious, organic material for your garden. I harvest worm castings approximately every 90 days and can yield 1-2 quarts of vermicompost. Photo: Patricia Vollmer.

If you have your worms happily buzzing in your homemade worm bin, and you’re seeing some happy worms through signs of their reproduction, after about 3 months, you might be ready to harvest some of the worm castings for your garden. After all, this is the point of the exercise.

Vermicompost is the end result of all of those worms processing through your kitchen scraps, shredded paper, and other organic material. It resembles plain old dirt, and shouldn’t have an odor. If you have one of those fancier worm bins, harvesting the poop will be quite simple, because the worms will migrate between bins as the food is available. You simply lift out the fully processed tray and work the castings into your garden.

However, with a DIY bin made from a plastic tote, you will have to get your hands dirty. With my bin, I tried to keep the fresh food to one side or the other of the bin, so I could constrain my harvesting.

Some tips for successful harvesting of a DIY worm bin:

  • Spread out lots of newspaper or other floor covering, this could get dirty.
  • Have a shop light or other kind of portable light handy, this will help keep the worms together for easier harvesting. If you don’t have a light such as this handy, you can work in a brightly lit room, or even outside. Be careful working outside, the worms can dry out quickly.
  • Make sure you have enough time to complete this task from start to finish. I needed about 60 minutes of focused work to do my own bin. You can’t walk away and leave the worms out for too long. They’ll stay in a ball and that’s stressful for them. Remember, happy worms make more worms.
  • A plastic boot tray or shallow plastic bin (such as an under-bed bin) lid is perfect for the picking and sorting tasks.
  • Have small buckets available for the worm castings. Preferably with a lid. If you’re harvesting in the off-season, the castings will keep till spring/summer.
  • Want to do it like the professionals? Get a sifting screen!

Worm Poop Harvesting Steps

Set up the light on one side, and dump the contents of the worm bin onto the tray. Photo: Patricia Vollmer.
Set up the light on one side, and dump the contents of the worm bin onto the tray. Photo: Patricia Vollmer.
  • Remove the large food debris and clumps of unprocessed shredded paper first.
  • Dump the processed contents of the worm bin onto your tray. Feel free to put the large pieces of food and clumps of shredded paper right back into the bin. The worms will join back soon.
  • Have the light on one side. This will force the worms to the opposite side of the pile of castings.
  • Start picking through the castings, trying to pull out as many worms as possible. I would get baseball-sized handfuls at a time. After pulling out as many worms as possible, the clump went into the harvest buckets.
  • Loose worms can go back into the worm bin with the large pieces of food and clumps of shredded paper
  • The majority of worms will be working their way away from the edges of the pile of castings, towards the center of the pile. Continue to pull clumps of relatively worm-free castings into your collection bucket.

In time, you’ll end up with a pile of worms with just a little bit of castings left.

The end result after filling two buckets with castings. Photo: Patricia Vollmer.
The end result after filling two buckets with castings. Photo: Patricia Vollmer.

You’ve done a great job! You can certainly toss this pile back into the worm bin and call it a day.

However, if you’re really ambitious, continue to pick out castings until you have nothing left but the worms.

MMM....worms.... Photo: Patricia Vollmer.
MMM….worms…. Photo: Patricia Vollmer.

The worms can go back into the bin, and you can go back to keeping up with feeding them and keeping the bin moist.

As for the buckets of castings, you can cover the containers and keep them in a dark place until needed. If you have some stray worms in the castings, it will continue to break down what you already have. Or you can add it to your garden right away. Mix it into the top couple inches of your garden soil for a great organic fertilizer.

Happy Vermicomposting!

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Patricia Vollmer is the proud mother of two emerging geek sons, ages 12 & 14. She serves part time as a meteorologist with the Air Force Reserve and is currently assigned to the U.S. Air Force Academy. Patricia blogs about her family's nomadic military life at Ground Control to Major Mom. Home is always where the Air Force sends her family, which for now is in Colorado Springs, Colorado. Hobbies include running, despite no one chasing her, sharing her love for Disney and Star Wars, and exploring the world with her boys. Ask her why the sky is blue at your own risk.