I do not think it is necessary to line your barrels before planting and the most important thing is to fill them with a quality potting soil that drains well. The Miracle Gro Brand of potting soil has fertilizer mixed in and would be a good choice. You can plant annuals, perennials and even vegetables in a container of that size and also blue berries and other shrubs. Japanese maples and other small trees would be happy growing in a half whiskey barrel for a number of years. Just make sure their drainage holes drilled into the bottom and that the soil drains freely so that wet soil does not rot the roots of your plants. Welcome to container growing and enjoy the adventure. Marianne Binetti