Should You Dry Worm Castings Before Using Them?

Worm castings are a great way to add nutrients to your soil. They can be used as an amendment for composting and hydroponics, as well as a soil conditioner for gardening. But should you let your worm castings dry out before using them?

You should not dry your worm castings before using them if you hope to add worms to your soil or begin vermicomposting. The dry castings will make the cocoons within the casting dormant, meaning no fresh worms. But if you are using them as fertilizer, you can leave them dry.

Ideally, your worm castings should be moist or damp but not sopping wet. Below, I’ll talk a little bit about why you might want to dry worm castings and how to do so. I’ll also cover whether worm castings will still work if they’re dry, and the benefits of worm castings. 

Why Worm Castings Are Sometimes Dried

Worm castings are made from organic matter, which means they’re naturally moist and full of water. To make worm castings suitable for sale, they have to be processed. The process often involves drying out the product by putting it in an oven or dehydrator. 

If you’ve used worm castings before, you may notice that they’re sometimes dried when you purchase them. This has less to do with anything garden-wise and more to do with the practicalities of storage. If you were to buy wet worm castings off the shelf, the moisture would make them moldy and unusable. Like most people, you probably don’t want to spend money on a product that will go bad soon after you buy it.

Also, if gardening centers had bags of wet worm castings, they might as well sell actual worms, which is less desirable for consumers. 

Some might say it’s better to dry the worm castings because of the scent. If you’re going to use them in your garden beds or hydroponic growing systems, you may have heard that you should apply them after they’ve been allowed to dry out completely. This is because fresh worm castings contain living microbes which can cause them to smell bad when they’re first added into the soil where plants use them. 

Still, this is probably a matter of personal preference. If you don’t want to deal with bad smells, you can put dry castings into your garden and moisten it from a distance with your sprinkler, hose, or watering can. 

But should you dry worm castings before using them?

I assume that the worm castings you’re working with are already moist. Drying them out will add an extra step because you’ll need to remoisten them before use. There’s little point in drying them out only to re-moisten them in the soil or bin.

Some gardeners dry out their worm casting so they can use the excess next season. If this is your situation, you’ll want to dry them out before you use them — but only if you’re not using them for a while.

Rehydrating Dry Worm Castings

If you’re using fresh worm castings, that’s great. However, other gardeners may buy worm castings already dried from the store. These will have the most living microbes inside of them and will be more potent than old castings.

Worm castings are great for your plants but can be a pain to work with if you’re unfamiliar with them. If you’re not careful, you’ll end up with dry worm castings that won’t help your garden because they won’t produce vermicompost or the nutrients you’re likely searching for. 

To rehydrate your dry worm castings: 

  1. Soak them in a bucket of water for about two hours. 
  2. After two hours have passed, drain off any excess water and let them sit overnight in a shady spot outdoors (or indoors if it’s too cold). 
  3. The next day, drain off any excess water again and then spread out the worm castings on newspapers or cardboard for another 24 hours. 

Your worm castings are now ready for use in your garden!

Worm castings are very smelly when they come out of the worm bin, so if you want to apply them directly onto your garden beds, this can be done. Just make sure you do it in a place with plenty of ventilation. That way, the smells can more easily dissipate and disappear — or at least, become more tolerable for anyone who passes by your garden. 

What To Do With Excess Worm Castings

If you have extra worm castings, there are a few ways to use them:

  • You can leave them in the bin and use them as fertilizer for your next crop.
  • You can save them by drying or dehydrating them.
  • You can store unused worm castings in a sealed container until next year.

If you have the time, letting them dry will ensure your castings are ready for use next season. You can do this in a paper bag or outside in the sun. Or, take them up with your soil and keep them away from moisture. 

This YouTube video shows you how to save excess worm castings and the end of the season:

You can also give extra worm castings to your neighbors or your local neighborhood gardening co-op. Alternatively, you can find someone willing to buy them. 

Worm castings are a valuable commodity, and it’s never wrong to have too many as long as your garden or vermicomposting system can handle them.

Will My Worm Castings Still Work if They’re Dry?

Usually, if you buy worm castings online or at a store, they’ll come to you dry. You might not be interested in the smell that comes with moist worm castings, or you may not want to have extra worms in your garden. But can you use them even when they’re dry?

Worm castings still work when dry, depending on what you are using them for. If you are using them as fertilizer, they can still help to add nutrients to your soil. However, if you want fresh worms to begin vermicomposting, they must be hydrated first. 

Worm castings are alive with microbes when they are fresh. Because of this, some people like to apply them right out of the composting bin. Doing this gets a little smelly, but you can certainly do it if you want to. If you choose to use fresh worm castings in your garden or landscape, simply remove what you need and spread it around where needed.

If you’re storing your worm castings for an extended period before application, it’s best to dry them first by spreading them on screens or drying racks. This will help kill off some of the microorganisms that may be harmful if ingested by animals or humans (though these microorganisms generally pose no harm).

Benefits of Worm Castings

Worm castings are an excellent way to enrich your soil and help it stay healthy. They can help keep away pests, support plant growth, and health, and even attract beneficial insects to your garden. 

Worm castings contain nutrients like nitrogen, phosphorus, and potassium. These are all essential for plant growth, so adding worm castings to your garden can help your plants thrive. The worms themselves also add organic matter to the soil, which improves its structure and makes it more able to retain moisture. This means you’ll need less watering over time!

Worms also aerate the soil as they move around in search of food, helping to improve drainage and increase oxygen levels in the soil. This helps protect against root rot or other fungal diseases that might otherwise be problematic when growing plants outdoors in rainy weather (or any other time of year!).


Worm castings are a great way to add vital nutrients and microbes to the soil in your garden beds or hydroponic growing systems. They can also help keep pests away from your plants, further enrich your soil, and help worms aerate your garden. If you’re unsure how best to use worm castings, try using dried castings and then moistening them before putting them in your garden. 

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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