Topiary plants are not particular species of plants, but rather the art of creating ornamental shapes with living plants. The practice has been around for centuries. Plants are pruned and shaped around a form to create shapes. You can buy topiaries, but it's also rewarding to prepare your own topiary plants. Topiary plants can be created from any shrub and flowering plant that responds well to trimming including ivy, holly, boxwood, hydrangea and rosemary. Buy a container that will support the topiary plant's mature height. Base the size on the form you purchase. For a tree design that is at least 4 feet tall, use a 24-inch container. Add a mix of potting soil and compost to the container. Put enough soil in to support the form. Place the topiary form in the middle of the pot, straight up and down, making sure the soil holds the form in place. Shovel in the rest of the potting soil, leaving 3 inches free at the top of the plant pot. Nestle the topiary plant at the base of the form, covering the roots with soil. The goal is to help the plant grow up and around the form. Water the topiary plant thoroughly until the soil is moist down to the roots. Apply a liquid fertilizer, following the label instructions, to encourage quicker growth. Use your hands to wind the vines around the topiary form. Don't pull too tightly; you just want to encourage the plant the grow around the shape. If needed, tie the plant in place with green dental floss. Check the topiary every day for moisture. Water the plant whenever the soil is dry to the touch. If the surface is dry, sprinkle the entire topiary with a hose or kitchen sprayer. You can also dunk it in a pail of water. Keep it moist but don't let the topiary plant sit in water. Prune the topiary regularly to keep its shape and keep the plant dense. Remove the stems that grow away from the form or those that look shaggy. Place the topiary plant where it will get bright sunlight. Keep it outdoors in the summer or in a windowsill.