Can You Put Too Much Worm Castings in Soil?

Vermicomposting is a tricky business. Things can be pretty straightforward when using food scraps to compost or working with your local compost site. However, worm castings are a slightly different story, and you may wonder if there’s such a thing as too much. 

You can end up putting too many worm castings in your soil if it doesn’t have the right resources to support your worm population. Worm castings contain worm eggs and the nutrients needed for vermicomposting. Consider the implications for your garden before deciding how many to add.

Worm castings are good for the soil, but there’s such a thing as “too much of a good thing.” Below, I’ll talk about what a worm casting is and why you may want to refrain from throwing handfuls into your garden. Additionally, we’ll talk about the benefits of worm castings for your garden. 

How Many Worm Castings You Should Put in Your Garden 

Worm castings are an inexpensive fertilizer that can be used to improve the health and productivity of your garden. Castings also contain humic acid, which helps plants absorb nutrients more efficiently. 

The process by which worms create castings involves breaking down organic matter into compost using bacteria and fungi in their gut; these microorganisms excrete enzymes that break down dead leaves and other waste products into nutrients that plants can use.

In general, you should put one cup (128 g) of worm castings for every cup of soil. A little less won’t be a big deal, and a little more won’t ruin your soil. However, if you add an excess of worm castings, it’ll be hard for your garden plants to get nutrients from the soil.

It’s important to remember that your worm castings are going to be adding nutrients to your soil. They are not a direct pipeline of nutrients to your plants. Your castings should be at a 1:1 ratio to ensure that there aren’t so many worm castings that the soil your plants grow in doesn’t have actual soil to take nutrients from. 

Additionally, if there are eggs in your worm castings, you should consider the implications of overrunning your soil with worms. The cocoons are within the casting and contain anywhere from 2 to 10 eggs. Worm castings don’t necessarily lead to large thriving populations of worms, either. Your worms need a healthy environment with plenty of soil and moisture. 

If you are interested in worm castings for their nutritional benefits, you should consider allowing the populations of worms that hatch to thrive in your garden. This will help to aerate the garden, and the worms will continue to break down nutrients and add them to your soil.  

What To Do With Excess Worm Castings

If you’re rich in worm castings, congratulations: that means your worms are vermicomposting and doing their jobs! However, it may feel like a waste to not use all the worm castings in your soil. As we discussed above, too many worm castings in your soil may be counterintuitive. Luckily, you can store worm castings.

Drying and Rehydrating Worm Castings

Worm castings are odorless and can be stored indefinitely. It’s not as simple as grabbing a handful and putting them in a jar. Your worm eggs may stay dormant within a jar, but if they do wake up and try to wiggle around, they’ll likely die or become too ill and weak to help your soul. You’ll need to dry out the worm castings before you store them.

Worm castings, especially straight from your soil, will likely be moist if you’ve ensured your garden has optimal conditions for worm life. Here’s a video of how to dry out super wet worm castings:

And afterward, this is how you can dehydrate them for later usage:

It would be advisable to dehydrate and store your extra worm castings (or give them away to fellow gardeners) rather than add an excess to your garden. Make sure you put them in jars, bags, or containers that won’t be easily exposed to any other elements. Additionally, leaving these things out in the sun may kill your worms. 

Ensure Quality of Life for Worms Born via Worm Castings 

You can have too many worm castings in soil, and it’s especially pertinent if you plan on letting the eggs of your worms hatch. Too many worms mean fewer resources for each of them. If you’ve never kept worms before, you might not know what you need to do to keep them alive.

If you decide to let the population of worms thrive in your garden via worm castings, you’ll want to ensure their environment is suitable. You can ensure the best worm castings for your garden or container plants by following these tips:

  • Use a good quality worm bin if you don’t want them directly in your garden.
  • Use good quality worm bedding (shredded newspaper, cardboard, peat moss, etc.).
  • Feed your worms well (they love coffee grounds). Put food in their bin regularly—but not right before bedtime!
  • Make sure the bedding is moist at all times. Keep it dark and warm, but not too hot. This will help them digest better and make more castings faster!

This way, your worms will give you their best abilities for nutrients and composting in your soil. Additionally, I’d recommend getting a worm tea or worm supplement such as the Petra Store Worm Teal (available on This can help boost the nutrients in your plants and comes with all-natural, super strong ingredients.

A moisture meter with a temperature function will help ensure that the garden isn’t too hot for your worms. You won’t need batteries and it takes less than 10 minutes to get a reading.

The Benefits of Worm Castings for the Garden

Worm castings are a concentrated organic fertilizer, and the cocoons make up one of their most important components. If this is the first you’ve heard that worm eggs are in your worm castings, you may be curious about the benefits. 

They are a good source of nitrogen, phosphorus, and potassium. And they also contain micronutrients like calcium, magnesium, sulfur, and iron. Worm castings are also full of beneficial microorganisms that help plants grow healthy roots by breaking down nutrients in the soil so they can be absorbed by your plants’ roots more easily.

The castings are full of beneficial fungi, bacteria, and nematodes that improve the structure of the soil. In addition to these beneficial organisms, nematodes may help keep harmful fungi and diseases away from your plants. Worm castings can suppress certain plant diseases.

There are several species of worms that create vermicompost, including:

  • Red wiggler worms (Eisenia foetida)
  • European nightcrawlers (Lumbricus rubellus)
  • African nightcrawlers (Amynthas agrestis)
  • Redworms or tiger worms (Lumbricus rubellus)
  • Composting worms such as banana slugs or red wigglers (Lumbricus rubellus)
  • African giant earthworms (Megascolex darwiniensis)

Some of these types of composting worms produce castings with different qualities. For example, red wigglers are one type of composting worm that can live in a wide range of temperatures, and they’re generally thought to be less likely to escape their confines than other types. 

Red wigglers can reproduce quickly if given access to food sources—most notably decaying vegetable matter—and they tend to digest those materials more slowly than other species.


There is such a thing as “too much of a good thing.” Too many worm castings won’t necessarily harm your garden or kill your plants, but it will stress them out and make it more difficult to grab the nutrients you were likely vermicomposting for in the first place. Additionally, too many worm castings in the soil may lead to an excess in nitrogen, which would be too much of a good thing.

Make sure to account for the worm babies that may be born from castings and give them the correct environment for a thriving life.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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