Thuja is a genus of evergreens commonly known as arborvitae. Used extensively in ornamental plantings, there are numerous cultivars available for a range of size, form and foliage color. Many can be recognized by their distinctive scale-like foliage and flattened branchlets. Two popular species, T. occidentalis and T. plicata, are native to North America. Insect pests include leafminers, spider mites and bagworms. Leaf and tip blights may affect arborvitae in forest, landscape and nursery settings.