border for flower beds

Unfortunatley I had to cut down a wild cherry tree due to ice damage. I'm thinking of ways to use the wood, and one way is as a border for my flower garden. I've cut smaller branches into 2" thickness and about 8 or 9" in diameter. I want to cut these in half and use as the border. I admit I'm not sure what I'm doing or if it will work, but no harm in trying. Does anyone know how I should treat this wood to keep it from rotting? I'm also curious if anyone has ever tried this and had positive results. Thanks for your help!!