Worm Castings Benefits: The Plant Superfood You’ve Been Missing

  • By: Charles Coleman
  • Date: May 31, 2023
  • Time to read: 6 min.

Have you ever wished for a magic potion to make your plants thrive? One that’s packed with essential nutrients, totally organic, and impossible to overdo? Well, nature has crafted such a potion for us, and it’s known as worm castings.

Worm castings, a nutrient-dense organic fertilizer derived from earthworms, have the potential to transform your garden from good to grand. From vegetables to flowers, fruit trees to herbs, and even delicate seedlings, worm castings are the ‘plant superfood’ that will supercharge their growth!

What are Worm Castings?

Earthworm excrement, known less glamorously as worm poop, is the organic fertilizer we refer to as worm castings. As earthworms digest compost, their waste acts as a soil enricher that’s teeming with nutrients. These tiny, football-shaped particles improve soil aeration and drainage, and boost water retention.

Sound impressive? You bet! But that’s not all worm castings bring to the table. Let’s delve deeper into this fantastic soil amendment.

Why Use Worm Castings?

There are countless reasons why worm castings can be your garden’s best friend. They pack all the vital nutrients that plants crave, while also enriching the soil where these plants grow.

Worm castings can be used on almost any type of plant and can be applied directly without risking plant burn. This versatile manure can be used as a top dressing, a side dressing, or as a soil amendment.

Creating worm castings through a process known as vermicomposting reduces garden and food waste that might end up in landfills, transforming it into a wonderful organic fertilizer. But the benefits of using worm castings in your garden soil don’t stop there!

Benefits of Using Worm Castings in Garden Soil

Worm castings are the gift that keeps on giving. Their benefits start with the worm itself, which digests organic materials, refining them and rendering nutrients, including minerals and trace elements, into their most usable form. These castings have a neutral pH of 7.0, and unlike other creature manures, they don’t smell strongly. Instead, they exude the pleasant aroma of forest soil.

But the benefits of worm casting extend far beyond pleasant aromatics:

  1. Enhances Soil Absorption: Worm castings increase soil absorption, ensuring moisture is consistently available to plants and preventing the soil from drying out entirely.
  2. Introduces Beneficial Microbes: Castings introduce numerous beneficial microbes, bacteria, and fungi into the soil, which promote healthier growth. The presence of humic acid aids in nutrient absorption.
  3. Improves Germination and Seedling Growth: Studies show that germination and seedling growth are enhanced when planted in earthworm castings. Think of worm castings as the “vitamin shot” for your plants.
  4. Removes Heavy Metals from Soil: Worms can remove heavy metals and other toxins from soil, making them useful in landfills and contaminated sites.
  5. Speeds up Composting Process: Adding red wigglers, a type of composting worm, to outdoor compost piles accelerates the composting process, enhancing the final product with worm castings’ benefits.
  6. Prevents Certain Plant Diseases and Pests: Castings can prevent diseases such as root and crown rots, wilt disease, and pests such as aphids, mites, and mealybugs.
  7. Improves Soil Structure: Worm castings enhance soil structure by increasing aeration, enhancing drainage, and promoting water retention.
Enhances Soil AbsorptionIncreases the moisture holding capacity of soil
Introduces Beneficial MicrobesInfuses soil with beneficial microbes, bacteria, and fungi
Improves Germination and Seedling GrowthEncourages healthier germination and growth
Removes Heavy Metals from SoilCleanses soil of heavy metals and toxins
Speeds up Composting ProcessAccelerates the decomposition of organic material
Prevents Certain Plant Diseases and PestsShields plants from diseases and pests
Improves Soil StructurePromotes soil aeration, drainage, and water retention

Doesn’t that make you want to introduce worm castings to your gardening routine?

What to Feed Worms?

Just like us, worms have their preferred meals. They love fruit and vegetable peelings, grains, breads, cereals, and even coffee grounds complete with unbleached coffee filters, and tea bags. However, avoid feeding them meat, dairy, or cooking oils.

When to Add Worm Castings to Garden Soil

There’s no ‘one-size-fits-all’ when it comes to using worm castings in the garden. Here are some ways to incorporate them:

  • Include it as part of your seedling starter mix
  • Add it when filling a new raised garden bed with soil
  • Use it directly in the planting hole when transplanting seedlings
  • Sprinkle it on top of the soil after lightly scratching it in after planting
  • Use it as a mulch around the base of established plants

What about Worm Castings Compost Tea?

You read that right! Compost tea is a nutrient-rich solution made by steeping compost in water, and worm castings can be used to make a perfect brew. Once the nutrients leach into the water, you can feed various plants or garden beds with this nutrient-rich “tea.”

From making your soil more absorbent and introducing beneficial microbes to improving germination and removing heavy metals from soil, worm castings offer an organic, nutrient-rich, and sustainable solution for your garden. The next time you plan to nourish your garden, why not consider adding worm castings to the mix?


How often do you use worm castings?

The frequency of application depends on the type of plants and their nutrient requirements. For houseplants, a feeding of worm castings once every two months is adequate. For vegetables, you can use worm castings at the beginning of the growing season and again midway through. Always follow a soil test for best results.

What are the disadvantages of worm castings?

The main disadvantage is cost. Worm castings are more expensive than traditional compost or synthetic fertilizers. However, the benefits they provide often justify the cost.

What plants are worm castings good for?

Worm castings can be used on almost all types of plants including vegetables, fruits, flowers, herbs, and houseplants.

What nutrients are worm castings high in?

Worm castings are rich in essential nutrients including nitrogen, phosphorus, and potassium. They also contain beneficial microbes and enzymes that aid plant growth.

Can too much worm castings hurt plants?

Unlike synthetic fertilizers, worm castings are not likely to burn plants even if applied in excess. However, like any amendment, they should be used responsibly to maintain a balanced soil ecosystem.

Are worm castings better than fertilizer?

Worm castings are a type of organic fertilizer, but they offer additional benefits like improving soil structure and introducing beneficial microbes. They are a more sustainable option compared to synthetic fertilizers.

Do worm castings raise or lower pH?

Worm castings generally have a neutral pH of around 7.0, so they don’t significantly affect soil pH.

Are worm castings acidic or alkaline?

Worm castings are generally neutral and won’t significantly alter the acidity or alkalinity of your soil.

How long do worm castings last in soil?

Worm castings continuously enrich the soil and can last for several months to over a year depending on the soil conditions and plant requirements.

Do worm castings add nitrogen?

Yes, worm castings are a good source of nitrogen, an essential nutrient for plant growth.

Can you mix worm castings with water?

Yes, you can mix worm castings with water to create a nutrient-rich compost tea for watering plants.

Do worm castings contain worm eggs?

Worm castings can contain worm eggs or cocoons, which might hatch into beneficial earthworms in your soil.

Can you plant directly into worm castings?

While worm castings are nutrient-rich, they shouldn’t be used as the sole medium for planting. They should be mixed into the soil or used as a top dressing.

How much nitrogen is in worm castings?

The nitrogen content of worm castings can vary, but it’s usually around 1-2%. While this might seem low compared to synthetic fertilizers, it’s important to remember that the nutrients in worm castings are more readily available to plants.

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