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Worm Castings - What are they? How do they work?

worm castingsWorm castings are the richest natural fertilizer known to humans. That's right: as little as a tablespoon of pure worm castings provides enough organic plant nutrients to feed a 6" potted plant for more than two months. Worm castings stimulate plant growth more than any other natural product on the market. Unlike animal manure and artificial fertilizers it is absorbed easily and immediately by plants. But Worm Castings don't only stimulate plant growth: they also enhance the ability of your soil to retain water (because of its texture), and it even inhibits root diseases such as root rot.

You can order worm castings in our catalog.

What Are Worm Castings?

Worm Castings contain a highly active biological mixture of bacteria, enzymes, remnants of plant matter and animal manure, as well as earthworm cocoons (while damp). The castings are rich in water-soluble plant nutrients, and contain more than 50% more humus than what is normally found in topsoil.


As the organic matter moves through the alimentary canal of the earthworm, a thin layer of oil is deposited on the castings. This layer erodes over a period of 2 months. So although the plant nutrients are immediately available, they are slowly released to last longer. The cocoons in Worm Castings each contain between 2 and 10 eggs that hatch within 2 weeks. This means that the process of decomposition are continued by the young earthworms in the soil, provided that the soil is loose, damp and rich enough in organic matter for the worms to stay alive.

The bacteria in the alimentary canal of the earthworm transforms organic waste to natural fertilizer. The chemical changes that the organic wastes undergo include deodorizing and neutralizing. This means that the pH of the castings is 7 (neutral) and the castings are odorless (they smell like a forest after rain). The worm castings also contain the bacteria, so the process is continued in the soil, and microbiological activity is promoted.

What Can Worm Castings Be Used For?

Worm Castings can be used as an ingredient of potting soil (as plant nutrients) for plants in and around the house. It can also be used as a planting additive for trees, vegetables, shrubs and flowers. When used as mulching material, Worm Castings will ensure that the minerals are absorbed directly into the soil when it is watered. Because Worm Castings will never burn plants, you can use as much of it as you like.

Benefits of Worm Castings

  1. The humus in the worm castings extracts toxins and harmful fungi and bacteria from the soil. Worm Castings therefore have the ability to fight off plant diseases.


  4. The humic acid in Worm Castings stimulate plant growth, even in very low concentrations. The humic acid is in an ionically distributed state in which it can easily be absorbed by the plant, over and above any normal mineral nutrients. Humic acid also stimulates the development of micro flora populations in the soil.

  5. Worm Castings increase the ability of soil to retain water. The worm castings form aggregates, which are mineral clusters that combine in such a way that they can withstand water erosion and compaction, and also increase water retention.


Recommendations and Quotes about Worm Castings

"Worm Castings outperform any commercial fertilizer I know of. The key factor is microbial activity. Research that I and others have done shows that microbial activity in worm castings is 10 to 20 times higher than in the soil and the organic matter that the worm ingests..."

"Earthworm castings are the best imaginable potting soil for greenhouses or house plants, as well as gardening and farming. It will not burn even the most delicate plants and all nutrients are water-soluble, making it an immediate plant food. The effect of earthworm castings used in any of these ways is immediately visible. They make plants grow fast and strong."

"Castings contain 5 times the available nitrogen, 7 times the available potash and 1 1/2 times more calcium than that found in 12" of topsoil. Therefore, castings are supplied with available nutrients. The nutrients are also water-soluble and immediately available to the plant. You will find that most potting soils have a nutrient life for 2 to 5 days, where worm castings will last up to 6 times as long. You will need 5 times as much potting soil to do the same job as worm castings. So in the long run, worm castings are much cheaper and do a much better job. Also, castings hold 2 to 3 times their weight in water. That means you water less and the pot will stay damper for a longer period. Worm castings will not burn your plants; unlike using any fresh raw manure (cow, horse, etc.) which can burn root systems if not applied properly. . . . The manure passes through the worms' digestive system producing rich organic plant food and a slow releasing fertilizer which allows for better growth."

How to use Worm Castings:

For Germination

Use 20 to 30% Worm Castings with sand as an excellent germination mixture. It will also ensure continuous and lush growth for about three months, without you having to add any other plant food.

As a Soil Conditioner

If you hoe a layer of barren soil, add a layer of Worm Castings and give it some water, you will be surprised at the growth of your first season's plants.

As a Fertilizer

Sprinkle Worm Castings around the base of plants or lightly dig it in, and then add water. They can also be sprinkled on a large scale with a spreader. Remember: you cannot use too much Worm Castings, they cannot damage your plants.

As a Liquid Fertilizer

Worm Castings can easily be mixed with water. Use 1 cup Worm Castings for every gallon of water and wait 1 week. This liquid mixture can be used as an excellent fertilizer or leaf foliate spray. It also helps to control insects. Many people prefer this method of application.

We have known for hundreds of years that earthworms are the best way to improve plant growth and to increase plant yield, such as fruit. Earthworm castings are a wonder product of nature. So if you care about your soil, and your plants, then now is the time to get rid of your Miracle Gro and to use this 100% natural product.

How Castings Are Grown and Harvested

Large wooden boxes are kept in a greenhouse with low light conditions and moist warm air. The boxes are filled with manure, cottonmeal, peat moss and other natural products and then worms are added.

As the worms eat their way through this material, they digest it and it breaks down and becomes worm castings. The worms are carefully separated out and the castings are bagged up for you. Many times worms leave tiny eggs in the castings which later hatch and become great worms for your garden to continue their work!