Plants draw water and nutrients up toward their roots through capillary action. This capillary action enables gardeners to water on an irregular basis while the plants take up water as needed. For this to happen, plants need a regular water supply, like the type provided by self-watering planters. Empty soda bottles make effective self-watering planters. They're free and accommodate most herbs and many flowers. Add some waterproof rope and you've created a self-watering hanging basket.
Cut a slit in the side of the bottle's label without puncturing the bottle. Pull off the label. Use hot water or a hairdryer to melt away any remaining adhesive.
Find the halfway point on the side of your bottle. Measure approximately 3 inches below the center point and make a mark with your permanent marker. Cut the bottle into two pieces with the utility knife at this mark. It's okay if the cut is a little uneven.
Reinforce the cut edge of the bottom half of the bottle with duct tape. Attach the tape so that half of the tape sticks up over the edge. Fold the top flap of tape over so tape covers the sharp edges and reinforces the plastic on both the outside and inside walls.
Use the utility knife to poke two holes about 1 inch apart in the reinforced part of the bottle with your utility knife. If you have a hole punch, use that instead. Place your holes at the center of the duct tape for added support and durability. Repeat with two more holes on the opposite side.
Measure how low you'd like your basket to hang. Cut two pieces of waterproof rope so they're double the length of this measurement. Thread the string through two of the holes from the outside in, then repeat on the other side.
Cut a hole in center of the cap with your utility knife. Cut a piece of water wicking cord 10 inches long. Thread the cord through the hole in the cap. Screw the cap onto the top of the bottle and make sure it's very tight. Pull the cord so 4 inches hang out of the bottle and 6 inches remain inside.
Grasp the inner 6-inch piece of cord in one hand and pull it taught. Use your other hand to fill this part of the bottle with soil. Fill in soil around the cord so the cord remains in the center of the soil-filled container. Add plants or seeds.
Fill the bottom of the bottle half full with water. Place the soil-filled top half of the bottle into the bottom, water-filled half. The cord and the plant's roots will pull water upward. Keep the bottom of the container filled with water.