Worm castings also referred too as “vermicast” is nature's secret ingredient, a powerful and sustainable organic fertilizer that brings a multitude of benefits to your soil, plants, and overall gardening success. And it all comes from worms! From improving soil health and texture to enhancing plant growth, vermicast has a wealth of advantages to unlock the full potential of your farm or garden. As we continue in posting some of our soil health blogs here at Herb & Under feel free to use this to reference some of the benefits of getting your herbs in top shape whether in ground, pots, or hydroponic setups. If you are curious about some worm casting options to purchase you can check our our blog here where we give some of our recommendations along with other soil amendments!

What Is Vermicast?

Vermicast is worm excrement or poop in other words. Some know it as worm castings (or more fondly by gardeners, black gold), but "vermicast" is the proper scientific term. Vermicast is the most pure form of worm excrement for gardening use and is different from vermicompost which is often a mix of bedding, food stock, and worm excrement. It’s made by creating a bin of worms, bedding, and food stock.

If you’ve never used vermicast in your garden, you might be turning your nose up at the idea of poop. But it’s a similar concept to manure. Vermicast is an organic and natural source of all the nutrients your plants need. And it’s good for the soil and the earth!

All About the Worms

Worms are detritivores, meaning they eat a mixture of decaying organic matter. Interestingly, they get their nutrients from the microbes that grow on decomposing plants and animals not necessarily the food itself. Before they start munching, they wait until a healthy colony of microbes has moved in. For more information on what worms eat or how does one gather vermicast check out our “start a worm farm for your house” course. We have been doing it for over 2 years and vouch for it’s efficacy in herbal gardening.

For vermicast, the best composting worms to use are red wigglers (Eisenia fetida) and European nightcrawler worms (Eisenia hortensis). They both have a fast metabolism and large appetite, making them the most efficient vermicast producers. To put that plainly, we mean that these worms eat and poop a lot! When you’re trying to use worm castings for your farm or garden, the hungrier the worms, the better. Red worms have been one of the most popular choices, but nightcrawlers are a close second. In fact, nightcrawlers can grow to be more than three times longer.

What You Feed Your Worms Matters

Not all vermicast is the same. The nutritional breakdown of vermicast depends on the type of bedding and food stock you use. For example, worms can be fed cow manure, horse manure, food waste, or paper waste, and each has a different nutritional content. One isn’t overarchingly better than another. In fact, some plants prefer vermicast from different sources. When choosing what kind of vermicast to use, consider the nutritional needs of your plants.

12 Benefits of Vermicast

From providing nutrients that spur plant growth to creating healthy soil, vermicast amendments offer a world of benefits to your farm and garden.

1. Source of NPK

As worms munch through decomposing material, they are performing garden magic. But it’s actually not magic. Through their digestive process, they break down the macronutrients in the detritus. Worm poop is full of simple nutrients that are easier for plants to absorb.

Namely, vermicast is rich in NPK, which stands for "nitrogen, phosphorus, and potassium." A good balance of those is what you want from any fertilizer, and worm castings offer these nutrients in the readily available form to your plants. Just note that vermicast is a “slow-acting” fertilizer compared to most chemical “fast-acting” fertilizers. So just keep that in mind as you use it in your garden. It is a marathon type application.

2. Provides Micronutrients

The humus from the vermicast also helps plants absorb other micronutrients. Along with the big three of NPK, vermicast helps plants access the binding sites for iron, sulfur, calcium, and magnesium. When compared with other natural fertilizers, vermicast soil amendments yielded the highest amount of nutrients.

3. The Right Amount of Fertilizer

Synthetic fertilizers can be shocking to your plants. Because of the larger particle size of vermicast granules, the nutrients are more slowly and consistently released into the soil. When you use worm castings in your farm or garden, you avoid overwhelming the soil with nutrients.

4. Benefits Soil Microbiome

Vermicast contains a diverse array of beneficial microorganisms, including bacteria, fungi, and other soil organisms. These microorganisms play a crucial role in maintaining a healthy soil ecosystem.

5. Nitrogen Fixing

Nitrogen fixation is the process of converting atmospheric nitrogen into a plant-usable form. Vermicast contains beneficial nitrogen-fixing bacteria, which can convert atmospheric nitrogen into ammonia and other nitrogen compounds that plants can readily absorb. When vermicast is added to the soil, these nitrogen-fixing bacteria establish a symbiotic relationship with plant roots, forming nodules where nitrogen fixation occurs. With more available nitrogen in the soil, the vermicast additions promote healthy plant growth and lush foliage.

6. Organic and Good for the Environment

Sustainability fans rejoice! Vermicast is an effective organic fertilizer, creating a healthy soil ecosystem without synthetic chemicals. Additionally, vermicast releases the nutrients gradually. That way, the nutrients go right where they need to: the plants! Unlike synthetic fertilizers, there isn’t a risk of nutrient leaching.

7. Improves Growth Hormones for Plants

Along with vitamins and minerals that enhance the soil, vermicast contains some natural plant growth hormones. These hormones help regulate plant processes, including growth and reproduction. When vermicast is applied to the soil or used as a foliar spray, it can enhance hormone production and distribution in plants, leading to improved root development, increased shoot growth, and healthier plant growth.

8. Aids in Disease Prevention for Plants

Because of the nutritive benefits, vermicast soil amendments can aid in disease prevention by enhancing the health and vigor of plants. When plants are provided with vermicast as a nutrient-rich amendment, they are better equipped to fend off diseases. Additionally, the microbiome that vermicast produces helps suppress the growth of pathogenic organisms by creating a competitive environment that limits the proliferation of plant diseases.

9. Increases Soil Water Retention

Vermicast amendments are beneficial for improving soil water retention in several ways. Basically, the organic matter present in vermicast acts as a sponge, absorbing and holding onto moisture. This increased water-holding capacity reduces the need for frequent irrigation. Secondly, vermicast enhances soil structure by improving its porosity and creating small channels and aggregates. This improved soil structure allows for better water penetration into the root zone. Lastly, the healthier, more nourished plants will have stronger roots that better absorb water when you do irrigate.

10. Creates Better Soil Texture

The organic matter present in vermicast also acts as a natural soil conditioner, enhancing the structure and texture of the soil. When vermicast is added to the soil, it helps break up compacted soil, improving its porosity and allowing for better air and water circulation. This improved soil structure creates a favorable environment for plant roots to penetrate and access nutrients and moisture more easily.

11. Prevents Soil Erosion

Vermicast not only creates healthier soil but also helps prevent soil erosion. It improves soil structure by enhancing its aggregation and stability, resulting in soil particles binding together and reducing the chances of erosion caused by wind or water. Because the vermicast increases the soil’s ability to retain water, it also reduces erosion caused by runoff.

12. Sequesters Carbon

By reincorporating organic matter into the soil, using worm castings as a soil amendment can actually help sequester carbon. The organic matter in vermicast is rich in carbon, and when incorporated into the soil, it becomes a stable form of carbon. This ultimately decreases levels of carbon dioxide in the atmosphere, which is a major greenhouse gas that drives climate change.

Setting Up a Worm Bin

The first step to making your own vermicast is setting up a worm bin. Start by selecting a suitable container that has at least a 10-gallon capacity. Plastic bins work great, but if you use wood, add a lining to keep it watertight. Add a layer of moist bedding material, such as shredded newspaper or coconut coir, at the bottom, then introduce a small group of red worms.

Bury the food under the bedding. Then cover the bin with a dry sheet of newspaper or lid with air holes. To maintain your worm bin, fluff the bedding about once a week and keep it at a consistent moisture level. You don’t want it drying out or getting soggy.

What to Feed Your Vermicomposting Worms

Worms thrive on a variety of organic materials, such as fruit and vegetable scraps, coffee grounds, tea leaves, crushed eggshells, pre-composted manure, and shredded paper or cardboard. Avoid feeding them meat, dairy, oily foods, or too much citrus. Be careful not to overfeed them, or you might just end up with a bin of rotting food.

How to Use Worm Castings in Your Garden

Using worm castings in your garden is simple and rewarding. Start by applying a thin layer of worm castings as a top dressing around the base of your plants. Gently work the castings into the top layer of soil, avoiding direct contact with the stems or leaves. For potted plants, mix worm castings into the potting soil or use them as a component when making compost tea. When transplanting or seeding, blend worm castings with the soil in the planting hole. Additionally, you can make a nutrient-rich vermicast tea by steeping a handful of worm castings in water for a day or two, then using the resulting liquid as a foliar spray or soil drench. When mixing with soil just remember that a 30-40% vermicast to soil ratio is preferable for optimum growing results.

Using Worm Castings will inevitably help your garden grow the best it can, help the quality of your herbs, and also improve the soil and climate along the way. In our opinion, it is a win-win!

Happy Gardening!

-The Johnstons