How to Use Worm Castings: A Step-by-Step Guide for Beginners
Quick Answer:
To use worm castings, add a small amount when transplanting in the garden, sowing seeds, filling pots or beds, or top-dressing houseplants. They boost nutrients, improve soil structure, and support healthy root growth—all without synthetic fertilizers.
Worm castings—also known as vermicompost or worm compost—are one of the best natural soil amendments you can use. Rich in beneficial microbes and plant-ready nutrients, castings improve soil health, strengthen roots, balance pH, and help retain moisture. But how exactly do you use worm castings? In this beginner-friendly, step-by-step guide, you’ll learn how to apply them in your garden, when sowing seeds, filling new containers or garden beds, or caring for houseplants—so you can grow healthier plants, naturally.
WHY WORM CASTINGS ARE SO GOOD FOR SOIL
Worm castings add micro life to your soil. Things like good bacteria, protozoa, fungi, and nematodes. These guys all do their part in breaking down organic material and releasing nutrients into the soil for your plants.
Worm compost is also full of nutrients. When worms eat, they absorb the nutrients they need from the food, and pass out the rest in a water-soluble form, which your plants soak up.
And what do your plants do with those nutrients? They grow stronger roots, which makes them healthier and more disease-resistant.
And if that’s not reason enough to love them, worm compost also helps balance the PH of your soil AND helps keep your soil moist and well aerated. Well aerated soil is fundamental for healthy plants and fertile soil.
But, how exactly do you use them? People often ask if they should use worm castings instead of soil, and the short answer is no. Castings are an amendment to soil, not a full replacement.
Here’s a step-by-step guide for the most common uses of worm castings.
PLANTING IN THE GARDEN
When you’re transplanting a plant or putting a seedling in the ground, dig a hole like you normally would. Then, grab a handful of castings and sprinkle them in the hole. Then place your plant on top of the castings and backfill with the soil you dug out. Finally, top dress around the base of the plant with a little more castings and water it all in as you would when planting any new plant.
That’s it. Pretty easy.
DIRECT SOWING SEEDS
If you’re direct sowing your seeds into the ground, make a trench or indent for planting as you normally would, and drop in your seeds. Then sprinkle a layer of worm compost directly over the seeds before covering with soil and watering them in.
This is a subtle but powerful way to support germination and early growth.
FILLING A NEW POT OR RAISED BED
If you’re starting a new pot or raised garden bed, this is an excellent time to set yourself up with a nutrient-rich foundation for growing. Simply fill your container or bed with your favorite soil mix. We suggest one that’s at least 5% organic matter. Then add a light layer of worm castings on top. This is a slow-release way to feed your plants. For optimal growth, you’ll want to reapply a layer of worm castings once a month.
INDOOR PLANTS
Vermicompost isn’t just for gardens. Anything that grows in soil will benefit from worm castings, and that includes houseplants.
To boost your indoor plants, simply sprinkle a light layer of worm compost across the surface of the pot. Then rake the castings into the top layer of soil (a fork works great for this) and water them in.
This is a great way to give your plants a boost of nutrients, without disturbing the roots. Do this once a month for happy, healthy plants.
Prefer to watch? Here’s the step-by-step in action.
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