Do Teabags Prevent Weeds From Growing In Your Garden? Here's What Our Master Gardener Says

I'm always looking for new ideas to incorporate into my garden. Now that I have transitioned from in-ground gardening to raised beds and large containers, like leftover mineral tubs, I don't have to spend as much time weeding. Still, no matter where or how I garden, there are weeds. When I heard about the possibility that teabags could prevent weeds from growing, I wanted to know if there is actually any science to back that up. I drink my fair share of iced tea in the summer, so I always end up with lots of teabags. As it turns out, there is not much to support this claim, but there are still many uses for teabags in the garden.

When I come across new suggestions or hacks, like TikTok's DIY club soda fertilizer, the first thing I do is look for supporting facts from reliable sources. TikTok is fun, but not exactly a reputable resource. Thankfully, scientists have studied the effectiveness of tea on seed germination.

What the science says

In a scientific study published in Agronomy in 2019, researchers tested the effect of different types of tea on the germination rates of seeds. They performed this study to see if any natural chemicals in tea could be used to replace the use of herbicides in the prevention of seeds. Their research determined that the tea that was most effective at reducing the germination rates of seeds originated in Vietnam and had a high caffeine content. These researchers concluded that it was most likely the caffeine rather than any other phytochemicals specific to tea that inhibited plant growth.

Although this research shows promise in furthering research on the effect of caffeine as an alternative to synthetic herbicides, it does not promise to be effective for the home gardener. For our purposes, we are talking about used teabags — they release caffeine when brewed. That's why I love it for a brisk afternoon pick-me-up! But there likely isn't much caffeine left for weed suppression. While teabags might not be helpful for weed suppression, they still contain organic material and nutrients that can improve the soil in your garden.

Using teabags in the garden

So, maybe teabags won't solve your weed problems, but don't toss them in the trash. Used teabags contain low levels of nitrogen and other trace minerals, all of which can add to the overall health of your garden. As organic matter, such as the tea and paper sachet, decomposes, it improves the soil structure. Since we have learned that it would take a massive amount of tea to inhibit seed germination, you don't have to worry about that affecting the growth of your flowers, fruits, or vegetable plants. In fact, we use coffee all the time to help our hostas flourish. We use them around lots of other plants, too.

The easiest way to use teabags in your garden is to toss them in your compost bin, but there are other options if you don't make your own compost. Dig a little hole between your plants and add a few teabags for slow-release fertilizer. If you use loose-leaf tea, you can just sprinkle your spent leaves around and under your plants. Keeping spent tea bags out of the landfill while using them as free fertilizer is a win for you, your plants, and the environment.