The Araucaria heterophylla, commonly known as the Norfolk Island Pine, is botanically a perennial evergreen conifer. The question of whether it is an annual or a perennial depends entirely on the climate in which it is grown. In its native habitat and similar warm regions, it is a massive, long-lived tree. However, in colder, temperate zones, it is frequently treated as a temporary, single-season plant, making its use more like an annual.
The True Classification of the Norfolk Island Pine
The Norfolk Island Pine, Araucaria heterophylla, is not a true pine but a member of the ancient conifer family Araucariaceae. It is endemic to Norfolk Island, a small territory in the South Pacific, where it thrives in a subtropical climate. In this natural environment, the plant is a woody, permanent tree capable of reaching heights between 160 and 200 feet. The tree’s symmetrical, tiered branching habit gives it the pyramidal shape popular in cultivation. It is officially hardy only in United States Department of Agriculture (USDA) zones 9 through 11, where it can be grown outdoors year-round.
Managing the Plant in Temperate Climates
The common confusion about the plant’s nature stems from its widespread use in climates colder than USDA Zone 9. In these temperate regions, the Norfolk Island Pine is incapable of surviving winter temperatures and is therefore grown exclusively in pots. When purchased around the holidays, it is often discarded after the season, effectively treating it as a decorative annual plant. The tree is highly susceptible to cold damage and will not tolerate temperatures below 50°F (10°C). Freezing temperatures below 35°F cause severe damage or death, requiring owners in non-tropical areas to bring the container plant indoors before the first cold snap of autumn.
Essential Care Requirements
To maintain the Norfolk Island Pine as a perennial houseplant, providing adequate light is necessary. It requires bright, indirect light to maintain its dense, symmetrical growth, though it can tolerate lower light for brief periods. Placing the plant near a south or west-facing window with filtered light is often ideal. Rotating the pot every few weeks helps ensure that light reaches all sides equally, preventing the tree from becoming leggy or lopsided.
Watering should be consistent, keeping the soil slightly moist but never waterlogged, as this can quickly lead to root rot. Water thoroughly when the top inch of soil feels dry to the touch, ensuring the excess water drains completely from the pot. Low humidity is a common issue indoors, especially during dry winter months when heating is in use. To counteract dry air, which can cause the soft needles to turn brown at the tips, humidity must be increased.
Increasing Humidity and Fertilizing
This can be achieved by placing the pot on a pebble tray filled with water or by grouping it with other plants. Fertilizer should only be applied during the plant’s active growing season in the spring and summer. Use a balanced, diluted liquid fertilizer every three to four weeks. Stop feeding entirely during the low-light winter months.