Quench your plant's thirst with worm castings

Who doesn't love plants? Or the fruits and veggies they produce? Sometimes plants need a little more help with growth or production, but animal manure stinks and you risk burning your plants with chemical fertilizer. For a more nature friendly option, you can try worm castings as a fertilizer, germination aide, or soil conditioner. 


Known as the richest natural fertilizer, worm castings stimulate plant growth more than any other natural product on the market. As little as a tablespoon of pure worm castings provides enough organic plant nutrients to feed a 6 inch potted plant for over two months, according to this website

Also known as vermicast or worm poo, worm castings can be used as potting soil 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, plant enthusiasts can use as much of it as they like on a plant. 

Using worm castings include helping plants fight off diseases, as the humus in the castings extracts toxins and harmful fungi and bacteria in the soil. It also balances the amount of heavy metals in organic waste and soil, and acts as a barrier to help plants grow in soil with unfavorable pH conditions.

Even in very small qualities, humic acid found in worm castings stimulates growth. This 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.

The castings also increase ability to retain water, and reduce acid forming carbon in the soil and increase the nitrogen levels. Organic plant wastes usually have a carbon-nitrogen ratio of more than 20 to 1. Because of this ratio, the nitrogen is unavailable to plants, and the soil around the organic waste becomes acidic.

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Damp worm castings contain a highly active biological mixture of bacteria, enzymes, remnants of plant matter and animal manure. The castings are rich in water-soluble plant nutrients, and contain more than 50 percent more humus than what is normally found in topsoil. Packed with minerals that are essential for plant growth, such as concentrated nitrates, phosphorus, magnesium, potassium and calcium, the worm castings also contain manganese, copper, zinc, cobalt, borax, iron, carbon and nitrogen. You can use worm castings on a plant without burning it like other fertilizers.

Unlike animal manure and artificial fertilizers, worm castings are absorbed easily and immediately by plants. Adding worm castings manure to the soil aerates and improves its overall structure while providing beneficial nutrients to plants. They are also effective for repelling many pests that feed on plants, such as aphids and spider mites.

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.

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Worm castings uses include plant germination, soil conditioner, fertilizer for potted plants, and liquid fertilizer in the form of worm tea.

Aside from purchasing castings from a gardening center or farmers market, a cheaper solution is to harvest your own castings. Worm bins or boxes can be purchased or constructed and come in various sizes and styles. You can also use plastic tubs, provided the worms have access to ventilation and drainage. If you decide to make the bins, they should be shallow, between 8 and 12 inches in depth. Make sure to have drainage holes in the bottom. If you stack your worm bins too full, they may start to stink. Smaller bins are recommended for home use because of storage space.  

When making a worm castings bin, layer the bottom with sand and strips of moist newspaper. Add compost, manure, leaf litter and another layer of moist newspaper strips and soil. Add worms and organic food, kitchen scraps, or garden waste. From personal experience, worms enjoy fruit, vegetables, and egg shells. Never give your worms processed foods.

When the bins get full of castings, you can use the dump and sort method to restart your worm bins. Simply lay out a sheet of plastic or newspaper to catch the contents of the bins and gently sort between worms and compost.  Collect your worms and add them to a fresh vermicompost bin. Collect the castings and use on your plants. If you can maintain your worm bins, your plant performance will skyrocket.

Jacqui Atkielski can be contacted via email at 

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