Pine Park (IMAGE) American Society of Agronomy Caption Milled pine bark, a byproduct of the lumber industry, is the basis of most growing media used to grow shrubs and trees in containers. Credit Jake Shreckhise Usage Restrictions Use with story only. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.