Particle board and plywood are composed of pieces of wood products that have been pressed and glued together. Although they are popular siding materials for storage units, they are not most people's first choice in regions where it rains a lot. For if water does work its way into these products (a possibility enhanced by their composite nature), then you're lost.
Outdoor Storage Sheds as Part of the Landscape - Integrate your outbuilding into the surrounding landscape. Plants can help outdoor storage sheds blend into a yard, rather than sticking out like sore thumbs. Establish garden beds around your unit and plant them with annuals or perennials. You can also install trellises up against the walls of outdoor storage sheds and adorn the walls with vine plants.