Help your garden grow. Tea leaves are rich in nitrogen, which plants need to grow. And because it’s also high in tannic acid, it’s an excellent fertilizer, especially for acid-loving plants such as roses, hydrangeas and azaleas. Once you’ve saved up about 10 used tea bags, rebrew a big batch of weak tea, transfer it to a watering can and sprinkle it all over your garden. Before long, you should see spectacular blooms!