Norfolk Island pine

Identification and origin

Araucaria heterophylla is a conifer in the family Araucariaceae. Despite the common name, it is not a member of the pine genus. It is endemic to Norfolk Island, a tiny Australian territory in the South Pacific between New Zealand and New Caledonia, where it grows in humid coastal areas, on basalt sea cliffs and in the interior rainforest. Discovered on Captain Cook’s second voyage, it has been in cultivation since the late 18th century and is now planted in many subtropical coastal regions, including Hawaii, southern Florida and coastal California.

Its outline is strikingly regular: a single straight trunk with horizontal branches radiating out in successive tiers, usually five per tier. The name heterophylla (“variously leaved”) refers to its two kinds of leaves: on young shoots, awl-shaped needles about 1 in long with sharp, incurved tips; on mature shoots, small, tightly overlapping scales. In the wild it can top 197 ft; the large, spiny female cones, 3–6 in across, form only on mature trees growing in the ground.

In a container it grows slowly and lives a long time. It is usually 3–6 ft tall and can approach 9 ft indoors.

Light

Light is the deciding factor. It needs bright light year-round: near an east window, a few feet back from a large south window, or at a west window if shielded from harsh afternoon sun. Aim for at least two hours of bright light a day. Strong light produces compact, symmetrical growth, but a little afternoon shade keeps the foliage from bleaching yellow.

Rotate the pot every week, or the tree will lean toward the window and grow lopsided. Kept too far from the light, it loses its dense form, stretches, sheds needles and then its lower branches, especially in winter.

Watering

Water thoroughly with lukewarm water when the surface of the mix feels dry to about 1 in deep, let the excess drain and empty the saucer after about 15 minutes. It likes consistent moisture: both a mix that dries out completely and a waterlogged pot make it drop branches, and standing water rots the roots. Growth slows in winter, so water less often then, but never let the root ball dry out.

Humidity matters as much as watering. It prefers relative humidity above 50%, which heated homes rarely provide. Set the pot on a tray of moist pebbles, group it with other plants or run a humidifier; a hygrometer lets you check the result.

Potting mix

A slightly acidic, fertile, porous soil-based potting mix with added peat moss (or a substitute) and coarse sand or perlite for drainage. The pot must have drainage holes. During the growing season, from spring to early fall, feed with a dilute liquid houseplant fertilizer every two to four weeks; stop in winter.

Temperature

It likes it cool: roughly 55–70 °F, ideally 61–70 °F by day and 50–64 °F at night. A winter rest at around 55–61 °F suits it well. It tolerates the warm, dry air of most homes and offices, but a house kept warm all year is not ideal. Keep it away from radiators, heating and air-conditioning vents, entry doors and moving air, which dries out the tips.

In the ground it is listed for USDA zones 9a–11b (winter lows around 19 °F); it is only reliably hardy from zone 10 and survives in zone 9 with a sheltered, warm microclimate. Outdoors it tolerates wind and some dry soil.

Repotting

In spring, every two to three years, once roots show at the surface or grow out of the drainage holes. The roots are delicate, so handle the root ball gently. Repot and fertilize only during active growth.

Pruning

It needs almost no pruning. Never cut the top: if the terminal shoot is broken or removed, the tree stops growing upward. A lost branch will not grow back either. Browning of the very lowest branches is normal with age; anywhere else it is a warning sign (see below).

Propagation

Only cuttings taken from the tip of the main stem produce a symmetrical tree; young shoots that come up at the base can also be divided off. Seed is possible but needs fresh seed and greenhouse conditions, and seed-grown trees have more widely spaced tiers than trees raised from tip cuttings.

Common problems

The same symptom can have several causes: check light, watering, humidity and placement before drawing conclusions.

• Browning needles and tips: air too dry, too little or too much water, hot or cold air currents, direct midday sun, or spider mites.
• Lower branches dropping: stress from lack of water, light or humidity, or from a nearby vent. Several years of low light lead to the same result.
• Lanky or lopsided growth: too little light, especially in winter, or a pot that is never turned.
• No more upward growth: damaged or missing terminal shoot.
• Pests: spider mites, which thrive in warm, dry air (rinse the foliage and raise humidity); scale insects and sooty mold (a black coating on the foliage).
• Diseases: leaf spot; in the ground, mushroom root rot.

Toxicity

No toxicity reported: it is listed as non-toxic to dogs, cats and horses. As with any plant, a pet that chews on it may still have passing vomiting or stomach upset. The needles on young shoots are prickly, so handle the plant with some care.