Plastic or wire baskets are available. Both have advantages and disadvantages. Plastic is inexpensive, easy to plant and is slower to dry out. Wire baskets allow more choices in size and planting arrangements. Many people find them more attractive.
Window boxes are usually plastic, wood or long wire baskets called hayracks.
Liners are used in wire hanging baskets to hold the soil and plants in position. Liners can be made of dried sphagnum moss or coconut fiber known as coir. Window boxes and baskets call for a strong support system. Remember that the containers will be much heavier when watered. Choose small, healthy young plants for planting.