Composite landscaping timbers are made of recycled wood, plastic and even automobiles--effectively reducing waste in their production. They are durable and low-maintenance, never needing to be painted or stained. They are relatively lightweight and held in place with metal stakes. They have a longer useful life than traditional wood timbers since they do not break down over time.
These are widely used plastics, according to Encyclopedia.com, that are a durable mixture of polymers and ethylenes and are used in a wide variety of applications. Polyethylene timbers are environmentally friendly due to their long life and have little need for maintenance. They are used in many applications, such as alternative landscaping.
A great alternative in your landscaping project is to use found objects as timbers--such as old railroad ties, parking curbs, rocks and stones. With a little imagination, you can build a unique landscape with little cost and reuse items that would have ended up in the garbage or are naturally occurring on your land.