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  • How do I use castings in potting soil

    Created by J cu ong on

    Hello –

    I tried to use super worm castings or frass as an organic fertilizer in my potted plants, but the leaves yellowed and died. How can I use them successfully in potting soil?

    Thanks in advance.

  • Author
  • #259994

    Eric Vinje

    Hello –

    A sort of super compost, worm castings are rich in nutrients and loaded with the microorganisms that create and maintain healthy soil. The beneficial microbes aid plant growth, help fight off disease and nourish your plants with readily absorbed nutrients that keep them healthy and productive. Clemson University Extension lists the following benefits of worm castings.

    • provides nutrients to the soil
    • improves the aeration and internal drainage of heavy clay soils
    • provides numerous beneficial bacteria
    • improves the soil structure’
    • increases the soil’s ability to hold nutrients in a plant-available form
    • increases the water holding ability of sandy soils

    Because vermicompost is usually made in modest quantities, it is often used as a top or side dressing for potted plants. Mixed with regular compost it adds a boost to garden soil. Blended with potting soil, it invigorates plants growing in containers, inside or out. Castings contain 4% to 5% nitrogen in a slow release form and should not burn plants when properly used.

    Gardens: Apply 5-10 pounds per 100 square feet and work into the soil.

    Top Dressing: Simply spread a layer (about 1/2 inch deep) around your favorite plants. Mulch and water thoroughly.

    Potting Mix: Add one part vermicompost with two parts compost, and 3/4 part vermiculite, perlite or coconut coir. Mix 1 Tbsp all-purpose fertilizer per gallon of soil.

    Shrubs & Trees: In late spring, mulch around plants with a 1-4 inch thick layer.

    Hope it helps!


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