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5 Benefits of Worm Castings for Indoor Plants

Worm poop? Using worm castings for indoor plants can be a game-changer.

worm castings for indoor plants

Let’s just get this out of the way: Worm Castings = Worm Poop. But, “castings” is a much more civilized way of describing the digested waste of your garden variety earthworm so we’ll just stick with that!

Worm castings, not unlike animal manure, provide rich nutrients and healthy bacteria for plants and vegetation and can be the secret superfood to help your indoor plants thrive. Here are five benefits of worm castings for indoor plants and how to buy or make your own worm composter.

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Nutrient-Rich Plant Food

Worm castings contain a mixture of bacteria, enzymes, remnants of plant matter, and broken down animal manure (and other existing compost). These castings are chock-full of plant nutrients and have over 50% more humus (broken down leaves and plant matter) than regular topsoil. Castings also contain plant-essential minerals like nitrates, magnesium, phosphorus, calcium, and potassium. They also contain manganese, copper, cobalt, borax, zinc, iron, nitrogen, and carbon. 

Worm Castings in a white spoon

Safer Than Chemical Fertilizer and Animal Manure

Worm castings are ready to be used as soon as the worm, well… you know… does its business. Best of all, castings won’t burn plants due to too much nitrogen like other chemical fertilizers or animal manure. Worm castings do contain about 5% more nitrogen than regular garden soil, but it’s in a slow-release form. The castings are covered by mucus that the worm secretes as they digest which causes the nitrogen to release slowly. (I know, I know, gross but cool.) 

The key takeaway here is that you can’t over-fertilize your indoor plants by using too many worm castings, which makes it a foolproof way for your plants to thrive. 

watering plant on windowsill

Enhanced Water Retention

The texture of worm castings mixed with soil helps the indoor plant hold moisture. Castings form mineral clusters that withstand water erosion and compaction while increasing water retention. Because of this, using worm castings for indoor plants can reduce the amount of time you need to water it, which also lowers your risk of root rot. 

Two Japanese Beetles are Eating Leaves

Natural Pest Resistance

Since we all hate those pesky chewing insects like aphids, whiteflies, and other hard-shelled plant bugs, you’ll be happy to know that worm castings are also a natural insecticide. They have a digestive enzyme called chitinase which kills these pests by dissolving their exoskeletons (…yep).

Indoor wormery composting

Cost-Effective (WIY: Worm It Yourself!) 

You can purchase worm castings products at a garden store (one brand is called Worm Power). But are you daring enough to build your own worm composter? By creating your own worm composter, you’ll save money and be more sustainable by composting your green kitchen scraps.

They’re pretty simple to put together and there are plenty of guides out there to choose from. Some basic materials used to build your own worm casting bin:

  • Plastic bin
  • Garden soil
  • Green ingredients (veggie scraps, eggshells, coffee grounds, grass clippings)
  • Brown ingredients (newspaper, corrugated cardboard, dried leaves)
  • Red wiggler worms

With the above items, you can create a simple worm composter quickly. Heck, you could make one this afternoon.

farmer hands in soil

How do I use worm castings in my indoor plants?

Use worm castings in the same way as other types of fertilizer. Use ¼ cup of worm castings for every six-inch diameter of your container/pot. Or you can sprinkle a few tablespoons at the base of the stems and water thoroughly.  Again, adding a little extra will not harm your plant (unlike chemical fertilizers). 

Are you ready to try worm casting compost? I’d love to hear about your experiences using worm castings for indoor plants!

Discover 7 top tips for growing, harvesting, and enjoying tomatoes from your home garden—when you access the FREE guide The Best Way to Grow Tomatoes, right now!

  • Donna Rae J.

    Can I just add worms to my potted plants and let them aerate the soil and leave castings in the soil?


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