Worm Castings

Worm Castings

If you’re looking for the best natural organic fertilizer there is, then worm castings (aka worm poop.. but don’t worry it resembles black organic topsoil and has an earthy smell) is your answer.

Worm castings boost natural plant growth better than other commercial fertilizers.  Also enhancing your soils ability to hold water and ward off unwanted diseases like root rot.

In fact, one tablespoon of worm castings can feed a 6″ potted plant for two months or longer.

The nutrients in worm castings are water-soluble and can be used immediately by plants.  Unlike artificial fertilizer, or animal manure.

What Are Worm Castings Exactly?

Earthworm castings are simply worm poop that have a super rich mix of enzymes, bacteria, and while damp may have some earthworm cocoons.  Along with containing more humus than is usually found in topsoil (around 50%).

Nutrients found in worm castings:

  • Concentrated nitrates
  • Magnesium
  • Potassium
  • Calcium
  • Phosphorus
  • Manganese
  • Iron
  • Cobalt
  • Nitrogen
  • Zinc
  • Copper
  • Carbon

It’s like a multi-vitamin pill for plants!  With the best part being that the plants can absorb the nutrients quickly and properly.  With no risk of plant burn.

Chemical fertilizers and animal manure will need to be broken down before the plant can use its nutrients.

The castings are created with organic matter is passed into the alimentary canal.   Deposited on the casting is a thin mucous oil layer.  Which will continue to erode for around two months.  Providing a slower, long lasting release of nutrients.  Alimentary canal bacteria does the magic of creating the natural fertilizer from organic waste.   Neutralizing and deodorizing in the process and encouraging microbiological activity in the soil.

The pH of earthworm castings is 7, making it neutral and odorless.  Some people say they have an earthy forest smell to them after a light rain.  With a crumbly dark consistency.   Similar to a black organic topsoil.

Worm castings will have one to ten cocoon eggs.  Usually hatching around the three week mark.  Cocoons are about the size of a grain of rice, or match head.  Usually in the shape of a lemon and can be white to light brown in color.

Fun Fact:  Worms are hermaphroditic, but to reproduce they still need a mate.

If you’re going to harvest worm castings yourself keep this in mind.  Eight worms could produce 1500 offspring in six months based on if they produced two cocoons per worm a week.    So, you really do not need more than a dozen worms to get started.

Benefits of Worm Castings

  1. Increases nitrogen levels and reduces acid-forming carbon in soil.  Which provides a healthier carbon-nitrogen ratio that helps plants thrive.
  2. Acting as a natural mulch the earthworm castings will help the soil hold water and minerals.  Which helps prevent erosion and replenishes aquifers.
  3. Increases development of micro flora which stimulates plant growth in the soil.  In the form of humid acid.
  4. Keeps soil pH balanced to prevent too high or low levels.
  5. Helps filter organic waste from heavy metals.
  6. Prevent plant disease with the use of bacteria and humus being released in the soil.
  7. Boosts a plants natural defenses to pests.
  8. Insulates plant roots from extreme temps.  Helping to prevent weeds and erosion.

Disadvantages of Worm Castings

Worm castings are not a “complete” fertilizer for certain plants.   And growth of some plants can be inhibited by some salts.

Acid-loving plants will also not do well in the pH of 7-8 range of earthworm castings.

The solution to these issues would be to mix the castings with another potting material.

Uses for Worm Castings

Here are some of the most common ways to use worm castings:

  • Potting Mix – Mix 1/4 of each: worm castings for nutrition, perlite for aeration, garden soil or sand for body, and coir for moisture.  Experiment with ratios for best results.
  • Soil Blocks – Use a soil blocker tool to grow seeds before transplanting.
  • Soil Conditioner – If you’re restoring a piece of land, a layer of red worm castings can really help pioneer plant growth.
  • Natural Worm Fertilizer – There is no better natural, organic nutrient you can use than worm fertilizer.  You can sprinkle it around plants, or dig some into the soil around a plant.  You can also use a spreader for a larger scale application.  Don’t worry about exact amounts.. as you cannot hurt your plants by using too much.  Great when transplanting.
  • Germination – Mix up sand with around 20-30% of earthworm castings for increased germination of seeds.  Once germinated the plants will be have enough nutrients from worm castings to grow for around three months.

Worm Tea

Worm casting tea is worm castings that are aerated in a bucket of water with a sugar source (feeds the bacteria). Usually for 24-48 hours.  This can be used in hydroponic systems as a sole source of nutrients.

If you don’t want a supercharged version of worm tea you can also just mix one gallon of water with one cup of earthworm castings.  Let the mix sit for around a week and it will be ready for use.

We prefer the aerated version of worm compost tea.  As it prevents anaerobic bacteria from growing and increases the beneficial bacteria count.

You can buy worm tea, but you will get the best product by making it yourself.  A small pond air pump works perfect.

Worm Castings For Sale

You can buy worm castings in most local garden centers. Although if you are in need of bulk worm castings they may not be your best source.  For that you should go online.   Here are some of our favorite organic worm castings for sale:



We will also be selling our own high-quality worm castings in our catalog.

Studies About Worm Castings

PDF Study – Earthworm Castings Increase Germination Rate and Seedling Development of Cucumber

Pablo Hidalgo, Maria Sindoni, Frank Matta, and David H. Nagel