Used tea grounds and fresh tea leaves contain nutrients and tannic acid that, when added to the soil, create a more fertile environment for garden, landscape and container plants. Because tea grounds are natural, organic matter, they increase nutrient levels and improve soil quality as they decompose. This, in turn, increases the level of activity by earthworms and other beneficial microorganisms. Tea grounds added to the soil also provide benefits, such as improved oxygenation, that create a stronger root system for your plants. Because plants take water and nutrients in through their root systems, the result is more vibrant, healthier plants.
It is important to note that not all plants respond well when tea grounds and used tea bags are added to the soil, directly or in compost form. The natural tannic acid inside tea leaves leaches into the soil with rainwater as tea grounds decompose, thereby lowering the soil’s pH and increasing acidity. This poses a problem for plants that require neutral to alkaline soils but creates the ideal conditions for acid-loving plants to thrive. Use fresh and used tea grounds only on acid-loving plants, such as rosebushes and ferns. The best way to monitor your soil’s acidity is through pH testing with a home test kit.
When applying used tea grounds to improve plant growth, mix the loose tea leaves directly into the plant’s soil, or spread the tea leaves around the top soil like mulch. When using tea grounds contained inside bags, remove the tea from the bag, or add the bags to the drainage layer of potted plants. If you want to add tea grounds to your vegetable and edible garden plants, do so indirectly, with organic compost. Adding straight tea grounds to garden soil during periods of active growth may disturb your garden’s pH balance or affect the flavor of your crops. Tea grounds make a healthy addition to organic compost piles, as they encourage decomposing bacteria. Without organic compost, tea grounds can be added to your garden soil prior to planting your summer or winter garden.
To ensure that tea grounds decompose properly, do not apply use tea grounds contained inside polyester tea bags. Stick with paper tea bags only, as paper is an organic substance that easily decomposes. Also, remove any metal staples from your tea bags before adding tea grounds to compost piles or placing them inside potted and container plants. Twice-brewed tea makes a nutritious, occasional, substitute for water. Be sure to allow the tea to fully cool to avoid shocking or burning your plants.