Pōhutukawa give a vivid display during the New Zealand summer, writes Gareth Carter.
OPINION
One of my favourite trees is the pōhutukawa.
There are so many selected cultivars with variations of flowering time, tree size and colour variations. Many are selections of naturally arising spores in the wild, while a few are intentional crosses.
This year we have had some spectacular red-flowered displays around the countryside. They look so bright and vibrant against a blue sky on a summer’s day.
They are not a quick-growing tree by any means with many established trees we see around the city likely 60-80-plus years old.
There are a number of varieties of metrosideros species that are grouped together under the widely recognised common name of pōhutukawa that we see in parks and streets. Not all are giant forest trees and a number can be grown in the home garden with some smaller-growing varieties suitable for patio pots.
Pōhutukawa have become very popular among many home gardeners. When New Zealand was settled by Europeans, they were found growing naturally close to the coastal areas of the North Island. From the Three Kings Islands southwards to Poverty Bay on the east coast and around the mouth of the Urenui River, just north of Waitara on the west coast. They also grew along the shores of some of the lakes in the Rotorua District.
Since then many species have been extensively planted in many parts of New Zealand, both inland and on the coast. They have been used as street trees in some cities, including Whanganui, and many have been planted in parks and gardens.
The largest pōhutukawa in New Zealand, Te Wahoa Rerekohu, at Te Araroa is said to be more than 300 years old and nearly 21m high with a spread of almost 40m.
We can also see good specimens in and around Nelson, on Banks Peninsula and as far south as Dunedin on the east and Jackson’s Bay on the west coast of the South Island. It is well known that the pōhutukawa grows best by the sea.
The familiar species Metrosideros excelsa is commonly referred to as the New Zealand Christmas tree. The Māori name pōhutukawa, “drenched with spray”, refers to the way these robust trees cling to rocky cliffs and endure wild ocean storms. It can grow into a massive spreading tree that overhangs the water, the huge branches growing out almost horizontally and forms deep roots that enable the tree to cling to steep banks and rocks and remain there.
Pōhutukawa trees often have aerial roots growing from low branches or the trunk. They can form a tangled mat or net and may join around the trunk or branch from which they arise. Only the larger roots may reach the ground.
The key feature is the vivid summer display during December and January when the tree is often completely smothered with its orange-scarlet to deep crimson flowers. These comprise dense, clustered stamens which open from powdery buds covering the tree. Fallen stamens can lay a red carpet on the ground.
Many birds are attracted to pōhutukawa flowers because of their copious nectar.
These trees are perfect in many landscaping situations; coastal hardy, they are a good first choice as a frontline seaside plant against prevailing strong, salt-laden winds.
In Whanganui, they can be planted in most sandy to heavy clay to free-draining soils that have been deeply worked and enriched with organic compost in a full or partial-sun position. Mulch 50mm to 75mm and water during dry periods while the trees are becoming established. Once established the trees are very drought resistant. Pōhutukawa normally branch from the ground but a single trunk can be formed with careful pruning and staking.
As a hedge or screen, regular trimming encourages and maintains the desired size to form an almost impenetrable barrier.
Pōhutukawa make good tub or container specimens for courtyards, patios or decks. They do well for several years before requiring repotting or planting out. Most pōhutukawa varieties respond well to being trimmed and, with an annual prune, can be kept significantly smaller than their growth potential.
Metrosideros excelsa is the species from which all the cultivars are derived. There is some considerable natural variation within the species through many plants in the wild. A number of selections have been made over the years, resulting in named varieties that are propagated vegetatively to offer certainty of colour, size and growth habit. Some of these varieties include:
Māori Princess is what we would all recognise as the iconic traditional pōhutukawa with spectacular, deep crimson red flowers from December into summer.
Metrosideros Springfire is an early flowering variety which has more orange-red flowers from spring to early summer. It grows about 4m high by 3m wide.
Metrosiderous Lighthouse is a selection of Metrosideros excelsa from Rangitoto Island in Auckland. Lighthouse has a more upright and tighter form than other pōhutakawa. It has the same dark, rich, green, oval-shaped leaves, crimson red flowers and rough dark brown bark. Red aerial roots may develop on the lower portion of the trunk over time. With all the typical features of a normal pōhutakawa tree, Lighthouse is better suited to where a smaller tree is required. Hardy to coastal conditions. Can be kept clipped to 1.8m. Grows to 4-5m in 15 years and a mature height of 6-8m.
Metrosideros Maungapiko is a cross between southern rata and pōhutukawa that incorporates the frost tolerance of the former with the large profuse flowers of the latter. It grows about 2m high in five years and 5m high when mature.
Metrosideros Kermadecensis Variegata is a fine, compact, variegated form, extremely hardy to coastal conditions and an ideal tub plant. The foliage is broadly margined creamy yellow and provides a garden with distinct colour. Some good specimens are along the GF Moore Drive entranceway to Springvale Park in Whanganui. These began as 150mm high plants in the gardens in front of the Memorial Centre forecourt and, when they became too large for the gardens, were successfully transplanted to their current site in the 1970s by parks personnel of the day.
Metrosideros Tahiti is a good smaller form of pōhutukawa that will fit into a courtyard garden or pot. It forms a beautiful shrub that grows about 1.2m high by 1m wide. It produces brilliant red flowers two or three times a year, mostly during the summer months. The foliage is a silvery-grey with red tips on the buds, making it most attractive.
Gareth Carter is general manager of Springvale Garden Centre.
'We want to take a very detailed specific look at what Whanganui needs' – Chris Bishop.