Recycled, non-soapy sponges make an interesting medium to grow herbs. Not only do you have an opportunity to recycle, but you can enjoy a distinctive and fresh herb garden indoors. Some popular herbs to grow inside sponges include any of the mints, basil, thyme and rosemary. Start an herb sponge garden indoors at the beginning of spring. You can also use the growing area as a focal point for decorating, such as a coffee table or front entrance table.
Rinse old sponges thoroughly under warm tap water for 5 minutes to make sure no chemicals or residue remains inside the sponge. Allow them to air dry for 24 hours.
Fill a large glass bowl three-quarters full of warm water. Drop the sponges into the bowl, allowing them to absorb the water. Only place enough sponges to fill half of the bowl.
Place herb seeds inside the sponge-growing medium. Press down the seeds with your thumb to get them inside the sponges.
Cover the bowl with plastic wrap. Poke six ventilation holes in the plastic wrap with a toothpick for air circulation. Place the bowl in a warm, dark location for four days.
Remove the bowl from the dark location. Remove the plastic wrap. Water only enough to dampen the sponges. Water from the side of the bowl to prevent disturbance of the herb seeds inside the sponge.
Place the bowl in a sunny location and allow herb seeds to grow.