The Norfolk Island Pine (Araucaria heterophylla) is a common houseplant often used as a small, living Christmas tree. While it exists in most homes as a manageable, potted specimen a few feet tall, its native environment reveals a massive tree. The height this species achieves depends entirely on whether it is grown in a climate it was genetically programmed for or one that severely limits its development.
The Tree’s Maximum Potential Height
In its native habitat on Norfolk Island, a small landmass in the South Pacific between Australia and New Zealand, this tree can reach imposing dimensions. When unconstrained by containers or unsuitable climates, the Araucaria heterophylla routinely grows to heights of 150 to 200 feet. This makes it one of the tallest conifers in the world, with a trunk diameter that can swell to 10 feet at the base.
Cultivated in subtropical or tropical regions, such as parts of Florida or Southern California, the tree will still achieve significant height, typically maturing between 60 and 80 feet tall. To reach these dimensions, the tree requires full sun exposure and well-drained, often sandy, soil, mimicking its coastal, cliff-dwelling origins. Once established, the Norfolk Island Pine exhibits a rapid growth rate, a stark departure from its slow-growing nature as a houseplant.
Managing Size When Grown Indoors
For the majority of people who grow the Norfolk Island Pine indoors, its height is actively restricted by the environment. As a houseplant, it is slow-growing, typically adding only three to six inches of vertical growth per year. Even with excellent care, a potted specimen will usually peak between five and eight feet tall over a decade, a size determined primarily by the container.
The most effective strategy for limiting the tree’s size is maintaining a pot-bound condition. Repotting should only occur when the tree is noticeably rootbound, usually every two to four years, and the new container should only be slightly larger than the old one. This restriction of root space stunts the overall growth of the plant.
To control the vertical height, the central leader, or the top growing tip, can be pruned. Cutting the top growth just above a whorl of existing branches will halt the upward progression at that point. This action, known as apical pruning, encourages a bushier habit, but it permanently disrupts the tree’s pyramidal shape, as the new growth will branch out rather than continue the single, straight spire. To maintain the tree at a fixed height, any new terminal buds that attempt to grow vertically must be consistently pinched off.
Factors Influencing Growth Rate
The rate at which the Norfolk Island Pine grows is dependent on specific environmental conditions, both indoors and out. Light availability is a primary regulator, as the tree thrives in bright, full sun conditions in nature. When grown indoors, a lack of sufficient light will slow growth considerably, often leading to a “leggier” appearance as the plant stretches to find light, and can cause the lower branches to yellow and drop.
As a species native to the humid South Pacific, the tree’s growth is highly influenced by air moisture. Low indoor humidity, especially during the winter when central heating is active, can cause the tips of the needles to turn brown, indicating a slowdown in healthy growth. Using a humidifier or placing the pot on a pebble tray filled with water helps create a microclimate with the 50% relative humidity the plant prefers.
Temperature stability promotes continuous growth throughout the year. The tree prefers a warm environment, ideally between 65°F and 75°F, and is sensitive to temperatures below 45°F. Consistent watering is necessary, as the tree requires moist soil, but overwatering will quickly damage the roots and inhibit growth.