How to Use Worm Castings - The Compost Culture (2024)

If you’re familiar with worm composting, then you know that as worms digest the food in your compost, they leave behind castings, which is a fancy way of saying worm manure. Manure gets a bad rap! It is an incredibly dense and rich fertilizer that your plants are going to love!

If you’ve got homemade worm bins, collecting the castings is easy. The worms move up the bins as you add new layers of food, leaving behind their castings. Simply collect the castings from the lowest bin and there you have it! Or, if vermicomposting isn’t your thing, you can buy worm castings, just as you would cow manure.

RELATED POST: Learn How to Make Your Own Worm Bins

The benefits of worm castings are you’re adding 100 percent organic fertilizer for your plants. It’s chock full of minerals and nutrients that your plants need to be strong and healthy.

Whether you’re planting seedlings, giving a boost to transplants or wanting to fertilize existing plants, worm castings are like superfoods to plants and has so many benefits!

5 Reasons to Use Worm Castings:

1. Your plants grow faster
2. Aerate your soil
3. Retain water
4. Keep pests away naturally!
5. Increase your yield (when growing veggies)

Simply mix worm castings in with your potting or ground soil when planting. Don’t be surprised to see you don’t need that much. It goes a long way because it’s so nutrient dense! Here are the instructions for mixing it with your soil:

How to mix worm castings with potting soil: It’s best to use 1 cup of castings for every 1 cup of potting soil for seedlings. For mature plants, you can use slightly less or the same ratio.

How to mix worm castings with transplants and regular planting: For perennials and vegetable plants, for every planting hole, use about a quarter cup of castings.

How to mix worm castings with shrubs or trees: For each planting hole (1-gallon containers) mix in 1 cup of castings. Be careful not to simplylayer the castings at the bottom of the hole. Mix with the dirt first. Putting straight castings can act as a barrier to the roots, making it difficult for your tree to root itself well.

You want to keep your worm castings dry, but also moist – so nothing airtight.

What you can do is take a plastic container (like a bucket or bin with a lid) and add some holes with a drill. Or you could take a plastic storage bag and poke a bunch of holes in it. You want your castings to keep breathing without being exposed to the elements.

An old yogurt tub works wonders here!

Unlike commercial fertilizer, worm castings won’t burn through the roots of your plants and flowers if you use too much. Your only issue with using too much worm castings is if you don’t have enough to share with all your plants!

Like stated before, a little goes a long way, so you don’t have to worry about packing your potting holes or containers with too much.

The only wrong way to use your castings is to use them without mixing with potting soil at the bottom of a planting hole.

Doing this can create a barrier between the roots of your plants and the soil. It is perfectly fine to add straight worm castings to the top off your plants or the bottom of a potted plant. Just be sure not to dump it in a planting hole without mixing with potting soil first.

You can buy worm castings from your local composter. We sell ours at the Miromar Farmers Market.

If you don’t have a local composter in your town, you can buy them online! Here are a few of our favorites on Amazon:

Don’t be put off by steeping your worm castings and making liquid fertilizer. It has all the benefits of your worm castings, but with the added benefit of hydrating your plants! It’s especially beneficial for container plants and hanging baskets.

You can further dilute it to make tea. Get more information about worm tea here.

To make liquid fertilizer out of your worm castings, use a ratio of half a cup of castings to 2 gallons of water and let soak for 24 hours.

You can tweak the ratio when making it, depending on how many plants you’ll be using it on. The liquid fertilizer doesn’t store well, so you only have about two days before it goes bad.

Check out this post to learn more about vermiculture and how to make your own worm farm.

Not interested in making your own? Buy one of these:

Check out these other posts to learn even more about compost:

• 3 Easy Ways to Compost in the Suburbs
• How to Use Fermented Banana Water as a Natural Fertilizer
• How to Make and Use Compost Tea
• 13 Ways to Keep Banana Peels Out of Landfills
• Compostable Products That Break Down in Backyard Compost Bins
• How to Make Your Own Worm Composting Bin