Scientists have discovered that applying relatively small amounts of vermicompost can improve germination rates, plant size, and growth speed—and there are some great lessons for gardeners buried in their study.
The scientists experimented with the impact of the Californian compost worm, Eisenia andrei Bouche, on arugula plants.
First, they created vermicompost over eight months, using home-style containers but in laboratory conditions.
They fed the worms a variety of shredded food waste, including banana, carrot, beet peel, fruit, squash, pumpkin remains, tea, and coffee.
They also maintained ideal conditions:
- Temperature: 20-22°C
- Humidity: 89%
- Aeration: The bedding was loosened regularly to keep oxygen levels high and prevent anaerobic conditions.
Once the vermicompost was ready, the scientists dug it into the top 10 cm of soil at a rate of 500 grams per square meter, comparing it to regular soil.
The results: Not just about size!
The increase in size and yield alone were impressive.
Plants in vermicompost grew 38% taller, developed 49% larger leaves, and had 80% more total biomass than those in untreated soil.
Growth was also faster, with plants growing twice as fast as those in normal soil.
The scientists also reported a higher germination rate (between 1.5-2 times) and an improvement in soil structure.
Why did it work?
The researchers suggested that high organic matter levels and nutrients levels may have played a role in the success of vermicompost.
However, other research suggests the real benefit of vermicompost is in the slow steady release of nutrients and its ability to stimulate microorganisms.
Learn more: The Magic Of Worm Castings (And How to Use Them)
A small study, but in line with other research
It’s always good to be cautious about drawing conclusions from a single, small scale study like this.
Indeed, this study only looked at the impact of vermicompost on a single plant, arugula. While the results are promising, there are many factors which could potentially skew the results.
However, things change if we consider alongside other research into vermicompost, which consistently show improvements in soil health, plant growth, and nutrient availability.
Research has also shown that vermicompost can boost growth in other plants; both beans and tomatoes have performed better with a vermicompost than when grown in regular compost.
Valuable lessons for gardeners
There were also some valuable takeaways for us gardeners in the study.
1. You don’t need fancy equipment!
The researchers used basic vermicomposting equipment, reinforcing the fact you can create vermicompost at home.
I use adapted storage bins to produce my vermicompost and get great results, but there are many options varying from ice-cream boxes to store-bought worm tray systems.
2. You don’t need to buy a huge number of worms
The researchers reported that by the end of the experiment, the number of worms had increased by 15 times in number.
If you want to try vermicomposting, you don’t need to make a large investment – you can start with a small number of worms and breed them over time.
3. Less is more
The researchers warned that applying too much vermicompost can lead to negative results.
I also find that even a small amount of vermicompost can make a huge difference in potted plants like chillies.
Final thoughts
Don’t be put off by the ideal conditions maintained in the study either – my worms have survived summer and winter with only a little bit of shelter in the garden. It might help that I use worms that are found naturally in my area – try to use native worms if you are doing outside vermicomposting.
To find out more about why it’s so effective, and how you can use it to improve your garden’s results, check out the guides below!
Read more
- The Magic of Worm Castings (Plus How to Use Them)
- Scientists Report: Vermicompost Grows Plants 38% Taller
- How to Build a DIY Worm Bin
- How Worms Help Compost
- Should You Add Worms To Your Compost
- Worms Produce Superior Compost Say Researchers
Source
Al-Tawarah, B., Alasasfa, M. A., & Mahadeen, A. Y. (2024). Efficacy of compost and vermicompost on growth, yield, and nutrient content of common beans crop (Phaseolus vulgaris L.). Journal of Ecological Engineering, 25(2), 215–226. https://doi.org/10.12911/22998993/176862
Edwards, C. A., Arancon, N. Q., & Greytak, S. (2014). Vermicompost as an effective organic fertilizer and biocontrol agent: Effect on growth, yield, and quality of plants. Reviews in Environmental Science and Bio/Technology, 13(1), 1–25. https://doi.org/10.1007/s11157-014-9347-1
Kallas, E., Rodikova, A., Maron, T., Myasnikov, A., & Gulik, E. (2025). Efficiency of vermicompost in a microplot field experiment. BIO Web of Conferences, 160, 01021. https://doi.org/10.1051/bioconf/202516001021