How to store and use worm castings

Estimated reading time: 7 minutes

Looking for tips on how to harvest, use, and store your worm castings? Many people start vermicomposting to produce their nutrient-rich compost for their house plants and garden. Then, after months of adding food and bedding- it’s time to collect the compost. 

How you collect the compost depends on the type of bin and your feeding method. In today’s blog post, I will share tips and tricks that I’ve used to harvest, store, and use my worm fertilizer.

Let’s not waste time and dive in!

Benefits of worm castings

Worm castings or poop is an all-natural alternative to chemical fertilizers. However, the castings’ exact nutrient and environmental benefits can differ depending on the food you provide for your worms. In general, worm manure contains beneficial bacterias and microbes, potassium, calcium, phosphorus, and nitrogen.

In addition to adding these crucial nutrients, worm casting also helps the soil retain moisture. 

Healthy soil has a vibrant mix of microbes, bacteria, fungi, and nutrients. 

Chemical fertilizers often only add nitrogen, phosphate, and potash. 

These chemicals are unable to add other types of significant biodiversity, such as bacteria and microbes. Instead, worm fertilizer reintroduces those items back into the ground in an all-natural way.

Some interesting research from Ohio State found that worm castings can aid in all stages of plant growth. Everything from helping seeds germinate more consistently to how much the plants eventually produce. They even gave the plants some natural immunities from common diseases and pests.

How to harvest worm castings

Over time, you will begin to run out of space in your worm bin. To make more room for your worms, you’ll need to remove all of the nutrient-rich compost, also known as worm poop.

We suggest that as you come to the top of the bin, you reduce the amount you feed your worms. Leaving your container uncovered allows your worms to break down any excess food before you harvest. Then, when your bin no longer has any visible paper or food scraps, you’re ready to harvest.

The easiest way for any beginner to harvest their compost is with light and a little time.

To harvest:

  1. Open your bin, and expose the bin’s contents to natural light or the light from the lamp.
  2. Wait 15 to 30 minutes with the top off; worms are light-sensitive and will burrow away from the light.
  3. Carefully remove the top inch of compost.

Once you’ve entirely removed the top layer, repeat the first step. Wait 15 to 30 minutes and clear away another layer. Eventually, you will get to the bottom. There is no need to remove all of the compost possible. Instead, dig down until the worms can no longer burrow any deeper. Add some food and new bedding, and you’re ready to start composting again.

How to store worm castings

After you get the worm castings out of the bin, you need to let them dry a little. Worms prefer to live in a moist environment. However, if you store the compost in this state, it will mold. How you dry out your castings often depends on how much you have. We find it easy enough to let the castings dry out in an upcycled cat litter tray.

After a few days, sometimes up to a week, much of the moisture will have evaporated. If the castings completely dry out, you will lose many of the beneficial microbes. Once you get it to the correct consistency, it’s time to find a storage container.

Finished pure worm compost
Finished pure worm compost in an upcycled takeout soup container. Note- the small air holes in the lid.

As you begin to transfer your worm compost to the storage container, you may want to sift your compost for any cocoons or missed worms. Try your very best to get any worms or cocoons out of your castings, as non-native worms can harm your local ecosystem.

Transfer the castings into a container that can keep in much moisture but still has some airflow. Many people use mesh sandbags, old protein containers, or any other upcycled bin. Whatever you choose to store your castings in, be sure that it has even just a tiny amount of airflow.

Worm castings stored in the right conditions can last up to three years

How to use worm castings

You can see there are so many great benefits to using worm castings. But, of course, how you use your worm castings depends on the application.

  • Add 15%-20% worm castings to a starting potting mix to help new or repotted plants
  • Till up to 33% worm castings into raised bed gardens.
  • Brew into a worm tea

How to make a basic compost tea

One of the most common ways to increase the benefits of worm castings is to create a compost tea. There are a lot of different methods and strategies between aerated and non-aerated compost tea. Compost tea is a way to increase the yield and beneficial microbes in the fertilizer.

For this recipe, you will need:

  • 1- a five-gallon bucket
  • 5- gallons of rainwater or purified water
  • 1- stocking or pantyhose
  • 1 cup worm castings
  • 1- fish tank air pump
  • 1- aeration stone
  • 2-3 Tbs cups molasses

Start by filling your five-gallon bucket with five gallons of rainwater. If you do not have rainwater, try to fill the bucket with non-tap water. Tap water is often highly chlorinated and kills many of the beneficial microbes you are trying to cultivate. Mix in the molasses.

Next, cut your stockings in two, so each leg is separated. Take one of the pieces of pantyhose, and place your one cup of worm castings inside. Let worm castings settle to the bottom and tie off the stocking. Place it in the bucket. Finally, connect the air-stone to the pump and aerated for 12-24 hours.


There you have it, your essential guide to storing and using your worm castings. There are so many different ways to harvest and use worm castings. These are just a few ways to help you get started along your journey. If you have tips or tricks that you’ve found beneficial in your worm composting journey, please share them in the comments below.

Thanks for reading, happy composting!