Despite sharing the common name "Emerald," these two plants belong to entirely different botanical families and have fundamentally distinct life strategies. The Emerald Green Arborvitae, scientifically known as Thuja occidentalis 'Smaragd', is a coniferous evergreen tree. It is a member of the Cupressaceae (cypress) family and is a gymnosperm, meaning it produces seeds that are not enclosed in an ovary (think cones). In stark contrast, the Emerald Tree Philodendron, or Philodendron bipinnatifidum (formerly P. selloum), is a broadleaf evergreen. It belongs to the Araceae (arum or aroid) family and is an angiosperm, a flowering plant whose seeds develop within a fruit.
The growth habits of these plants highlight their evolutionary paths. The Emerald Green Arborvitae is a woody tree with a dense, narrow, pyramidal or columnar form. It grows a single, central trunk covered in fibrous, reddish-brown bark, from which horizontal branches covered in scale-like leaves emerge. It is a true, self-supporting tree that can reach heights of 10-15 feet in landscaping. The Emerald Tree Philodendron, however, is not a tree in the true botanical sense. It is a large, non-climbing (self-heading) type of philodendron that develops a thick, tree-like stem or trunk as it matures. Its structure is characterized by huge, deeply lobed leaves that emerge directly from this central stem on long, sturdy petioles. It gives the appearance of a small tree but lacks the complex branching structure of an arborvitae.
The foliage is one of the most obvious points of differentiation. The Arborvitae possesses tiny (1/4 inch), scale-like leaves that are pressed closely against the stems. These leaves are adapted for water conservation and cold tolerance, and they maintain their emerald green color throughout the year. The Philodendron's leaves are its defining feature. They are large, glossy, and thin-textured, with a prominent central vein and deep, pinnate lobes. These leaves are adapted for capturing dappled light in the tropical understory. While evergreen in warm climates, they lack the cold-hardiness of the arborvitae's foliage.
Their reproductive methods are a key botanical distinction. As a gymnosperm, the Emerald Green Arborvitae reproduces via cones. It produces small, inconspicuous pollen cones and seed cones on the same plant (monoecious). The seed cones are woody and small, typically around 1/2 inch long. The Emerald Tree Philodendron, an angiosperm, reproduces with a specialized inflorescence typical of the arum family. This consists of a spike of tiny flowers (the spadix) surrounded by a modified leaf called a spathe. The spathe is often white or greenish, and the entire structure is quite showy compared to the arborvitae's cones.
Their native environments explain their differing cultural needs. The Emerald Green Arborvitae is a cultivated variety of a species native to northeastern North America. It is exceptionally cold-hardy (USDA zones 3-7) and thrives in full sun with well-drained soil. It is adapted to temperate climates with distinct seasons. The Emerald Tree Philodendron is native to the tropical regions of South America, specifically Brazil, Argentina, and Paraguay. It is a frost-tender plant (USDA zones 9-11) that prefers warm, humid conditions, partial shade, and consistently moist (but well-drained) soil. It is an understory plant adapted to high humidity and filtered light.
