The Araucaria heterophylla, commonly known as the Norfolk Island Pine, is a popular houseplant, but it is often misunderstood. Despite its common name and resemblance to a traditional Christmas tree, it is not a true pine, but rather a conifer belonging to the Araucariaceae family. This species is native only to the small Norfolk Island in the South Pacific, where it is accustomed to a mild, subtropical climate. In its natural habitat, this plant grows into an immense tree, reaching heights of up to 200 feet with a symmetrical, pyramidal shape. The plant’s outdoor survivability depends on replicating the consistently warm conditions of its native environment.
What Hardiness Zones Mean for the Norfolk Island Pine
The United States Department of Agriculture (USDA) Hardiness Zone system is the standard for determining which plants can survive winter outdoors in a given location. This system maps the country based on the average annual minimum winter temperature, which is the defining factor for plant survival. For the Norfolk Island Pine, the outdoor landscape range is strictly limited to USDA Zones 10 and 11.
These zones represent subtropical to tropical climates where the average lowest temperature remains above freezing, specifically between 30°F and 40°F for Zone 10 and above 40°F for Zone 11. The plant’s classification as a tropical conifer means it requires mild conditions to thrive and cannot withstand the seasonal freezing typical of temperate climates. Regions like parts of Southern Florida, Southern California, and Hawaii have the necessary frost-free or near-frost-free environments for the Norfolk Island Pine to grow outdoors.
Temperature Thresholds and Survival Limits
The Norfolk Island Pine possesses a low tolerance for cold. While it prefers ambient temperatures between 65°F and 75°F, it can withstand brief dips in temperature slightly below 50°F (10°C) without immediate harm. However, sustained exposure to temperatures below 40°F (4.5°C) will begin to cause serious damage to the plant’s cellular structure.
The visible signs of cold stress include the browning of the foliage, often starting at the tips and progressing inward, followed by branch dieback. The plant’s survival limit is typically reached around 35°F (1.6°C), and exposure to freezing temperatures of 32°F (0°C) or below for any extended duration is usually lethal. Once the plant’s internal water freezes, the rapid expansion destroys cell walls, leading to the death of the plant. This low thermal threshold is why the plant is almost exclusively treated as an indoor specimen across most of the United States.
Year-Round Care Outside Its Native Zone
Outside of Zones 10 and 11, the Norfolk Island Pine must be grown as a container plant that is moved seasonally. The plant should be placed outdoors during the warm summer months to benefit from natural light and air circulation. A good rule of thumb is to move the plant outside once nighttime temperatures are consistently above 60°F (15.5°C) and to bring it back inside before the first forecast of frost or when temperatures drop into the low 50s.
During the winter, when the plant is indoors, its care requirements shift considerably. The plant needs bright light, ideally from a south-facing window, to maintain its dense, symmetrical growth. In low-light conditions, the branches may stretch out, resulting in a leggy appearance.
Maintaining proper humidity is important, as heated indoor air can be dry and cause the foliage tips to turn brown. Grouping the plant with other houseplants, placing it on a pebble tray filled with water, or using a room humidifier can help keep humidity levels above the preferred 50% threshold. Watering should be significantly reduced during the cooler, darker winter period, only moistening the soil when the top inch feels dry to the touch to prevent root rot.