Western red cedar is the best to be used as a base material because it is naturally resistant to rotting and acts as a natural insect repellent. The looks of western red cedar is also gorgeous, so it is not only a suitable but also beautiful material for wood pergolas. An old growth of cedar is twice as expensive than a new growth one. But the downside is when they are treated with chemicals, the can sometimes loose some of their natural luster and beauty. In addition, the chemical placed n the wood can have it’s own effect damaging the wood. Nevertheless, it cna be stained with your color choice.