The classic hanging basket is a wire basket, filled with sphagnum moss and a sphere of cascading blooms. Here's how to fill a wire basket, plus some suggestions on what to plant.
1. Select a wire basket at least 12 inches in diameter and 8 inches deep for best results. The larger the container you choose, the more types of plants you can combine, which makes for a showier and lusher bouquet. Soak long-fibered sphagnum moss in water for several minutes. Squeeze excess water from the moss and press it around the inside of the basket and just over the top to conceal the wire rim.
2. Poke holes in the moss at various spots inside the basket. Space plants closer together than you would in the garden. Tuck a plant into each hole (plant trailers such as ivy around the lower edges of the basket), then fill the basket to the rim with potting soil.
3. Set a cluster of plants in the top of the basket by pulling back some of the soil with your hands. Firm the soil; water well. Make sure the moss is holding in the soil all around the basket; add more if needed. Add a slow-release fertilizer in spike or tablet form to keep nutrients from leeching out with frequent watering. Water daily.