Smooth Hydrangea (Hydrangea arborescens) is a structural shrub with large and showy white inflorescence in summer. They prefer moist soil in shade to part shade where they grow to 6 feet tall, making them a good choice for planting in shaded slopes or basins. Companion plants include Cinnamon Fern (Osmunda cinnamomea) and Great Blue Lobelia (Lobelia siphilitica).
Leaf spot, rust, and powdery mildew can be a problem. Prune stems to the ground in late winter to promote sturdy fresh growth.