Built-up Herb Garden - Scattering tea leaves

What are the pros and cons of scattering used tea leaves in a herb garden?

Thanks to various connections we’ve made recently, we have been brewing a lot of tea-infused mead. That leaves us with a lot of spent tea leaves. I was planning on dehydrating them a bit before throwing them away, but I heard that there is still plenty of nutrition left in them. I thought about scattering these tea leaves in our herb garden, but I was curious about the pros and cons, so I did some research!

1. The benefits of scattering used tea leaves in a herb garden

① Expect soil improvement. Used tea leaves are rich in dietary fiber and minerals (such as potassium, magnesium, and calcium), and mixing them into the soil can improve its water retention and aeration. In particular, mixing them into clay-heavy soil can improve drainage, potentially helping herbs establish better roots.

② Acting as organic fertilizer. Used tea leaves contain small amounts of nitrogen, phosphorus, and potassium (N-P-K), which are essential nutrients for plant growth. Green tea leaves are especially rich in potassium, which can help promote plant disease resistance and root growth.

2. The disadvantages and precautions of scattering used tea leaves

① Excessive use can cause nutrient overload or stunted growth. Although used tea leaves contain potassium and polyphenols, scattering too much can disrupt the soil's nutrient balance. Excessive potassium, in particular, can inhibit the absorption of other minerals (like calcium and magnesium), potentially hindering herb growth.

② Undecomposed tea leaves can cause mold and rot. You need to be careful, as scattering tea leaves as they are can easily lead to mold in damp environments. They may also rot and emit a foul odor if scattered in areas that don't dry out easily or during the rainy season.

③ It may have the opposite effect on some herbs. The caffeine and polyphenols in used tea leaves affect the soil. Too much of these components could inhibit the germination or growth of certain plants, so it is recommended to start with a small amount.

3. Effective ways to utilize used tea leaves

① Dry them before scattering. Since scattering them while wet can cause mold, make sure to dry the tea leaves thoroughly first. Drying them in the sun or using a microwave makes them easier to handle.

② Use them after composting. Composting used tea leaves along with other food scraps and fallen leaves creates a more stable organic fertilizer. Fermentation also helps mitigate the effects of caffeine and polyphenols.

③ Use them in balance with other organic fertilizers. Instead of scattering only tea leaves, using them in combination with leaf mold, rice bran, or chicken manure makes it easier to maintain a balanced soil nutrient profile.

④ Spread on the surface instead of mixing directly into the soil (mulching). When using tea leaves as mulch, spreading a thin layer on the soil surface can help suppress weeds and prevent the soil from drying out. However, since they affect the soil as they decompose, be sure to replace them periodically.

4. Summary

Used tea leaves are an organic material useful for soil improvement in a herb garden, but excessive use can disrupt the nutrient balance or lead to mold.

To use them effectively:

✔ Dry them before scattering

✔ Use them after composting

✔ Balance them with other organic fertilizers

I plan to incorporate them into our routine while keeping these points in mind! Also, since it seems they don't decompose very easily, I will try mixing them into the soil in small amounts while observing the results. My goal is to cultivate herbs in a sustainable, circular way.