Commonly known as the New Zealand Christmas Tree, Pohutukawa (Metrosideros excelsa) brandishes appropriately red bottlebrush flowers during November and December in its native land. In the United States, the tree usually blooms from late spring to midsummer, where it may provide a flowery form of fireworks for Memorial Day or the Fourth of July. Thriving outdoors in U.S. Department of Agriculture plant hardiness zones 9 to 11, this Christmas tree must be raised as a bonsai or house plant elsewhere.
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If grown under ideal conditions, Pohutukawa may reach 60 feet in height. The tree can send out aerial roots from its gray and corky trunk or branches when it needs to anchor itself in place. Its oblong 1- to 5-inch leaves feel felted when young, but their surfaces eventually turn a waxy dark green while the undersides remain silver and furry. Although Pohutukawa's flowers are generally some shade of red, from crimson to rust, the tree can also produce pink or yellow blooms.
To sow Pohutukawa, you will need to acquire fresh seeds from the gray and fuzzy 1/4- to 1/2-inch seed capsules in the fall. If you can’t plant them right away, place them in the refrigerator until you are ready to do so, as they don’t remain viable for long. Because the seeds are fine and chaffy, they should be scattered over the surface of sterile seed-starting mix and barely covered with a sprinkling of sand. If their mix is kept damp, they will begin to germinate within one week, and should be kept in bright conditions out of direct sunlight. Once the seedlings are three months old and about 1/2-inch tall, you can transplant them into individual small pots and begin acclimatizing them to more sun. Don’t plant them outdoors until they are at least two years old.
Most frequently found on ocean coastlines or lakeshores in its native habitat, the tree requires very well-drained soil, preferably in full sun. Vulnerable to root rot, it won’t tolerate boggy conditions. Although it will grow most rapidly in fertile ground, it can survive -- in stunted form -- on very little soil at all. Because its roots can be aggressive, keep it away from sidewalks and septic tanks. Young trees shoot up rapidly, sometimes adding 1 to 2 feet per year, while older ones grow more slowly.
In the U.S., stressed Pohutukawa trees may be attacked by pests such as the Eucalyptus longhorned borer, which makes oozing holes in the bark, and the Eugenia psyllid -- whose presence is betrayed by pitted leaves and sooty, black mold. Under normal circumstances, both are controlled by natural predators, so you can prevent infestations by keeping your tree watered and healthy. Pohutukawa may also suffer from the fungus disease anthracnose, which causes dark spots on the leaves. You can forestall this problem by keeping the tree in full sun and away from nearby trees or buildings, so that air can circulate around it freely.