Organic Gardeners All Agree That Adding This Natural, Non-Toxic 'Black Gold' to Your Soil Will Turbo Charge Plants
Discover exactly how worm castings benefit plants, and how to use them
If you are looking for a natural way to grow strong plants and have healthy soil, worm castings may be the ‘black gold’ you are looking for. It is a nutrient-rich, sustainable alternative to synthetic fertilizers that not only benefits plants but also boosts the long-term health of your garden.
This non-toxic marvel is easy to get hold of. You can create worm castings at home by having a wormery in your garden, or buy bags of worm castings from garden centers or online retailers. However you source them, worm castings make a fantastic fertilizer for a wide range of plants, including shrubs, flowers, vegetables, herbs, and houseplants.
To extol the virtues of worm castings for plants, I chatted with compost and organic growing experts to show you why, how, and when to use this sustainable gardening switch. Trust me, from now on you’ll leave those synthetic fertilizers on the shelves and reach for the worm castings instead. Your plants and your soil will thank you for it.
Trees, shrubs, and perennials all benefit greatly from worm castings
What Are Worm Castings?
Without sugar coating it, worm castings are the waste products of earthworms, or earthworm poop.
They may not sound like much, but they do make a super fertilizer. Produced through vermicomposting, which is another term for worm-based composting, this process sees earthworms digest organic material, such as food waste, and turn it into valuable material.
There are two ways to get worm castings for plants. First, home gardeners can use a wormery to make compost. A wormery contains two compartments. One where the worms live, and the waste is added, and another where the worm castings are collected.
You can either make your own wormery for compost or buy one, like this five-tray worm composter at Amazon, into which you put your kitchen scraps or garden waste to transform into homemade compost.
Rather than make your own, there are lots of options to buy bags of pre-made worm castings for plants. Such as this 2.5-pound bag of Worm Bliss premium earthworm castings, also available at Amazon, to use around the garden.
Shop Worm Castings for Plants
The Benefits of Worm Castings for Plants
Worms process food and garden waste into nutrient-rich castings to use in the garden
Worm castings are a superb, sustainable way to make plant fertilizer, and offer many benefits over store-bought synthetic products, including supporting long-term soil health and supporting a garden’s ecosystem.
Lauren Click, the founder of Let’s Go Compost, explains that worm castings are ‘non-toxic’ and ‘safer’ than synthetic fertilizers, as they actively improve garden soil rather than cause sudden chemical changes.
‘Worm castings contain beneficial microbes that improve how nutrients move through soil to plants,’ adds the compost expert. ‘They also improve soil aggregation and increase microbial activity in the soil, supporting long-term plant health.’
On the other hand, Lauren warns: ‘Chemical fertilizers provide fast nutrients but can degrade soil structure.’
As a natural ingredient, worm castings are safer to plants, and there is no risk of burning them by over-fertilizing, as with chemical products. And they offer immediate benefits, such as green growth from boosting the soil nutrients, fewer pest and disease issues, and improved moisture retention.
‘Worm castings don’t just supply nutrients; they support a living soil ecosystem,’ explains Siobhan Shaw, sustainable gardening expert and founder of Growing to Give. ‘They contain beneficial bacteria and fungi that help plants absorb nutrients more efficiently and improve overall resilience.’
‘Because they’re fully broken down, worm castings are immediately available to plants while continuing to enhance soil structure long after application,’ adds Siobhan. ‘This makes them ideal for gardeners who want long-term results, not quick fixes.’
Lauren is the founder of Let's Go Compost, a 501(c)(3) non-profit with a mission to make composting free and accessible throughout the United States. Lauren works both in the dirt (literally) with public schools and community gardens, while also remaining focused on the big picture - working with large organizations and policymakers to ensure composting accessibility and affordability are kept front of mind as infrastructure is developed.
How to Use Worm Castings
There are different ways you can go about fertilizing with worm castings. Gardeners can use them as top dressing, mix them directly into the soil, or brew a nutrient-rich worm tea.
The simplest way to use worm castings for plants is to top dress your existing plants, or, to put it simply, just sprinkle the worm castings on the surface of the soil around the base of trees, shrubs, or perennial plants.
An easy alternative is to mix the worm castings into the soil at planting time to help new plants get established in flower beds or vegetable gardens.
Another option is to make worm tea, by mixing one part worm castings and three parts water for a nutrient-boosting liquid feed.
This brew is perfect for flowers, vegetables, or houseplants and can be used to water plants every two to three months during the spring and summer growing season for a quick boost of essential plant nutrients.
Are Worm Castings Good for All Plants?
Worm castings can be added as a topdressing to raised beds
Worm castings are an excellent feed for a broad range of plants. ‘One of the greatest advantages of worm castings is their versatility,’ says Siobhan Shaw. ‘Nearly every plant benefits from them, but some respond especially well.’
Those that really benefit from worm castings include ornamental trees, shrubs, and flowering plants.
These plants, including roses, fruit trees, perennials, and annuals, benefit from healthier root systems, sturdier stems, and more blooms thanks to the strong root development and improved soil fertility.
Lauren Click adds that vegetables and herbs are also greatly beneficial, as worm castings improve how the plants absorb nutrients. She claims: ‘Heavy-feeding crops like tomatoes, cucumbers, and peppers respond especially well due to their higher nutrient needs.’
You also see improvements in potted plants in container gardens and indoor plants as worm castings help with soil structure, moisture retention, and nutrient uptake.
Siobhan is the co-founder of Growing to Give, a dynamic global non-profit dedicated to transforming community-focused food security and agriculture through sustainable farming and gardening practices. Siobhan is a passionate advocate for women's empowerment in agriculture, mentoring women who aspire to careers in the field. Siobhan also continues her decades of podcasting as the host and co-producer of the health and well-being podcast titled Real Talk.
FAQs
Are Worm Castings Good for Indoor Plants?
Yes, worm castings are beneficial for indoor plants and offer a safe way to fertilize houseplants. Lydia Beaumont, a gardening expert for Gardeners' Yards, says that worm castings are ‘great’ for houseplants, particularly foliage plants. ‘Houseplants that use worm castings develop stronger root systems and have a more vibrant growth,’ says Lydia.
‘Houseplants that thrive from worm castings include pothos, monstera, and peace lilies. They help these leafy plants retain much-needed moisture and can help reduce stress from inconsistent watering.’ To use worm castings on houseplants, top dress the surface every 2-3 months or use worm tea when you water plants.
Lydia Beaumont is a gardening expert for Gardeners' Yards - a trusted online resource for gardeners to grow, inspire and discover. Whether crafting stylish table settings or transforming a garden into a personal oasis, Lydia loves making every space stunning and comfortable.
Will Worm Castings Produce Worms?
Worm castings are waste material, but on occasion, they can contain cocoons that may hatch in warm soil. The chances of the material containing cocoons are much higher with homemade worm compost, but any young worms that hatch will help to keep the soil healthy.
If you prefer not to use worm castings for plants, you should still stick to natural feeds. In that regard, compost, manure, or leaf mold are the best fertilizers for a vegetable garden and flower beds.
When it comes to compost, whether you start a compost heap from scratch to make your own or purchase bags of pre-made compost to spread onto your beds (such as this 10lb bag of premium organic compost at Amazon), compost is full of nutrients that it slowly releases, and benefits soil structure and water retention.
This lightweight, portable, worm bin with a latching lid has two trays and is made from mostly recycled materials. You can make worm castings on a deck, patio, or balcony.
This worm composting bin allows you to do vermicomposting in a raised bed. Bury the bin into the soil and fill it with kitchen waste and worms.
One pound (around 1,000) redworms to add to your worm composter. They are known to process up to a pound of organic waste per day.
