Disadvantages Of Worm Castings: Before You Start

  • By: Sam Richards
  • Date: August 2, 2023
  • Time to read: 6 min.

If you’re a gardener, you’ve probably heard of worm castings. They’re often touted as a wonder product that can improve your plants and soil. But there are also some disadvantages to using worm castings that you should be aware of. Here’s a look at some of the potential downsides of using worm castings in your garden.

What are worm castings?

Worm castings are nutrient-dense soil produced by earthworms. The secret sauce of these castings lies in their humic acid, an organic compound that promotes healthy growth in plants when added to the soil. They can boost water retention, and microbial activity, and even increase the presence of beneficial bacteria and fungi. It has been observed that worm castings help plants reach maturity faster, too! That said, they come with a few setbacks: they can be difficult to locate and expensive to purchase, making them a less accessible solution than some other fertilizers. Additionally, if overused they can saturate the soil with nutrients, leading to root rot issues.

Buy and try the worm castings yourself

What are the disadvantages of worm castings?

Worm castings are generally seen as a beneficial addition to soils, however, the use of them does come with some drawbacks. They can be difficult to find in an unrefined state and often need to be processed before application. They require a lot of labor when used in large-scale gardens and greenhouses, making them an impractical option for those growing on a larger scale. Worm castings may also contain contaminants that could be dangerous to other organisms or crops if not managed properly. Let’s take a closer look!

They can be smelly

Worm castings are an amazing way to add much-needed nutrients to your garden soil, but they come with a few drawbacks. One of the most noticeable is their pungent smell. When used without proper ventilation, the strong odors generated by worm castings can quickly fill up a room and make gardening projects lethally unpleasant. Luckily, proper ventilation can easily combat this issue, but it is something that should always be considered when using or storing worm castings near populated areas.

How to Resolve

The best way to avoid odor issues associated with worm castings is to ensure that the container they are stored in is properly ventilated. This can be done by keeping the container outdoors or placing a fan near it to help circulate air. Additionally, using smaller containers for storing and spreading worm castings can also help minimize odors since less material will be exposed at any given time.

Finally, covering the top of the container so that no worms or liquids can escape will also reduce odors significantly. Additionally, wearing protective gear such as gloves and a face mask when handling worm castings will also help protect you from unpleasant odors.

They can attract pests

Before adding worm castings to your garden oasis, it’s important to be aware of potential pests (fruit flies) they may attract. According to experts, if the castings are kept too wet or left exposed to the elements, they may become a breeding ground for pesky bugs and other critters. Plus, overwatering them can leave you with a smelly sludgy mess on your hands, making you wish you had just thrown in a scoop of regular old soil.

So if adding worm castings to your garden is something you’re considering, it’s best to ensure they are kept in the right conditions and monitored carefully in order to keep any unwelcome guests away.

How to resolve

  • Make sure the worm castings are not too wet.
  • Cover with a thin layer of soil or mulch to protect from sun and wind exposure.
  • Keep an eye out for any pests that may be attracted to the area and take appropriate action if they appear.
  • Store any unused castings in a cool, dry place away from direct sunlight and moisture.
  • Use natural pest deterrents such as neem oil or diatomaceous earth if needed.

They can be messy

They can be quite messy when spilled it’s difficult to know how much of the mixture should go back into your garden beds in order for the soil chemistry to remain balanced. Plus, worm castings can attract flies and other pesky critters that you may not want scurrying around your space. That’s why it’s important to store worm castings somewhere secure to avoid these problems while taking advantage of their benefits!

How to resolve

One way to avoid the mess that can come from using worm castings is to use a commercially-available product such as vermicompost. Vermicompost has been pre-processed and screened for size, which makes it easier to work with and less likely to attract bugs or other pests. It’s also usually free of weed seeds and other potentially harmful elements, so you can be sure that your garden beds are getting only the best nutrients. You can then spread this vermicompost directly onto your soil or mix it into your existing compost heap as needed.

You should also take care when handling worm castings by wearing gloves and a mask if necessary.

Do you already have everything in place for composting?

They can be difficult to store

Worm castings require a safe space that does not experience wide fluctuations in temperature or humidity, making it tricky for gardeners without the perfect storage environment on hand. The material also takes up a lot of room, so having enough space is essential for keeping the product securely tucked away until it is ready to use in soil. For those who are looking to take advantage of this natural fertilizer in their garden, having an appropriate place to store the castings is key.

How to resolve

The best place to store castings is in a cool and dry area that does not get too hot or humid. The temperature of the room should be maintained between around 50 and 70 degrees Fahrenheit, and any dramatic changes in humidity can cause problems for the product.

Some gardeners like to use ceramic containers with tight-fitting lids to ensure that their castings remain secure until they are ready to use them. It is also important to keep the material away from direct sunlight or other sources of heat, as this will reduce its effectiveness.

For those who do not have suitable storage space available, there are some options that allow you to keep your castings fresh until you need them. For instance, some products come in bags with resealable lids, which can help to maintain their moisture levels. Additionally, some products come in sealed plastic tubs, which can also be used for storage purposes.

They can attract animals

Worm castings can attract animals such as moles and gophers that you wouldn’t necessarily want roaming around. If this is a problem where you live, it is best to make sure to have something like a fence or barrier around the areas to which you apply the worm castings. After all, we don’t want any visitors stealing our hard-earned veggies!

How to resolve

To avoid attracting animals, it’s important to ensure that the worm castings have been applied correctly and not too thickly. It is also wise to cover up any areas where you’ve placed the worm castings with mulch or other soil covers to prevent any unpleasant smells from drawing animals in. Additionally, keeping your gardens clean and free of debris can help minimize the possibility of unwanted visitors. Finally, if there are critters near your garden, make sure to remove them as quickly as possible so that they do not return for more nutrients!

Why worm castings are hard to harvest

Although worm castings may seem like an easy solution to planting, harvesting them is often a difficult process. Worm castings can be hard to spot in the soil, especially when mixed in with other materials. Additionally, it takes time and effort to collect enough of the castings for use in the garden.

For these reasons, many people opt for purchasing commercial-grade worm castings instead. Not only are they easier to find and purchase, but their quality is usually much higher than that of homemade versions. With that said, if you’re dedicated and determined enough, it is possible to harvest your own worm castings – just make sure you have all the necessary tools and know-how before getting started!


Worm castings may have environmental benefits, but there are also some disadvantages that need to be taken into consideration. One of the major downsides is storage which can be an issue as worm castings need to be kept in a specific environment and temperature; if not stored and handled correctly they can spoil quickly. Furthermore, using too much of it can also lead to a salt build-up in the soil, negatively affecting the quality of plants. In conclusion, while worm castings have their own advantages, one should take extra precautions when handling them due to some potential drawbacks.

  1. I’m wondering why the worm castings smell bad, or smell at all. I’ve found that my castings never have anything other than a light organic odor and have never attracted any pests. As long as they are high quality castings that don’t contain any unprocessed food they shouldn’t smell. The only time they do have a bad odor is when they are kept in a closed container with no airflow, since they will go anaerobic, meaning no air. Even a worm bin shouldn’t smell bad.
    As for attracting moles…that is possible anywhere worms are present and moles are a common place. The castings won’t lure them in any more than any other organic material, such as compost or manures.
    It’s easy enough to store castings in a 5 gallon bucket with either a cloth over top, holes in the lid or sides of the bucket. It does help to roll the bucket every month or so to allow air to reach the bottom but I’ve left mine in an unheated basement for over six months without rolling them and have had no issues. Some cocoons may hatch and those worms will continue to work through the organic material left behind.
    It is important to keep them moist as you mentioned and not drenched.
    The only time adding too much is an issue is if more than 10% is added since they won’t do any good and can cause stunted growth if more than 25% is added. This would be a lot of castings in a standard garden or pot so it’s unlikely that someone would add that much.
    I like that you are trying to spread the word about worm castings but there is a ton of misinformation here that may make someone think twice about using them. For anyone out there reading this…please take this article with a grain of salt and look further into castings before choosing not to use them. Yes, they can be a bit expensive but raising your own worms can lower that and also reduce your own waste! A worm bin shouldn’t smell or attract pests if foods are frozen before being added (to kill fruit fly eggs) and the food is buried under a couple inches of bedding. The only pest I’ve had issues with in the past several years is fungus gnats and that was my own fault for bringing in an infested plant. They are easy enough to eradicate using mosquito bits, so if caught wary can be eliminated in a few weeks.

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