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Olearia ilicifolia is a vascular native shrub or small tree endemic to New Zealand. The name Olearia having come from a 17th century German scholar (Johan Gottfried Olearius) and ilicifolia from the similarities in leaf appearance it shares with other named species. Common names include Maori-holly, mountain holly, hakeke or hakekeke and New Zealand holly. It is a spreading shrub or small tree of the family Asteraceae and has largely serrated and undulating dark grey-green leathery leaves. Conditions decide the growth of Olearia ilicifolia with the plant ranging from bushing shrubs to mature trees which can grow as big as 6m high x 3m wide. Flowers are yellow or white that group in florets which tend to gather towards the tip of the plant's branches, along3 with its leaves.

It is closely related to the sub-alpine Olearia macrodonta, with which it shares the names mountain holly and New Zealand holly, however, it is much more common than Olearia macrodonta. It is found in lowland and sub-alpine forests from sea level to 1,200 metres (3,900 ft). However, it can also be found on ridgelines, river flats and river edges in the Western South Island, it prefers a cool shady climate. This relatively common species was last categorized as 'Not threatened' in 2009.

Description
Mountain holly is a much-branching, spreading shrub to small tree that grows up to 6m tall with a trunk that can be as thick as 35cm in diameter. When found in abundance, free from dense scrub, this Mountain Holly forms a dome-like canopy. This is due to the plants crown being umbrella-shaped which occurs as a result of the trunk and main branches being forked repeatedly. The branches of this tree start right from the base, so there is no large branchless trunk like you might see on other trees.

The woody bark is an odd colour that has been described as dark orange-grey or brown on the trunks and bigger branches. As the bark ages, it begins to peel in long strips of no particular width and coil up. This bark grows annually in papery layers and is deciduous. This species can have many branches or vary few depending on the conditions it is exposed to. The smaller twigs and stalks that expand from the bigger branches are darker in colour and can sometimes be almost black.

Its leaves look nasty with sharp and jagged spiny margins, the leaves are usually dark green or greyish in colour and are very stiff/rigid with a yellow midrib. These leaves range from 50 to 120 mm long and 10 to 20 mm wide so are very narrow. The leaves cluster at the apex of the plant's branches. Each shoot on a mature tree produces an average of five full leaves each season. Leaves of the Hakeke are categorized as simple leaves that are strongly undulated with an alternative arrangement.

Flowers are formed on the upper leaves of the plant's branches, the flowers bloom into corymbs (flat/slightly convex heads), from the auxiliary buds of these leaves. These flowers are white or yellow which produce white or yellow flower heads that look like petals (florets). The flower heads themselves are small with a 1 cm diameter. During the fruiting season, masses of small brown seeds are produced which sit on top of detachable pappus (tufts of hair), which are light and fluffy for dispersal.

Distribution
This is an endemic species which means that it only occurs in New Zealand. However, other genus and species within the Asteraceae family can be found outside of New Zealand. Olearia ilicifolia can be found south of the Herangi and Pukeamaru Range in the Waikato. Below this area in the North Island, it is distributed throughout the South Island and Stewart Island but occurs predominantly around Fiordland and South Westland. While its habitat ranges from lowland to subalpine forests, it prefers Habitat s with high soil fertility, often in areas frequently disturbed such as slips, river terraces and shingle slopes. This species is suited to habitats that are constantly exposed to erosion processes.

Life cycle
New leaves grow at a certain time of year and at different speeds depending on which buds they are being produced from. Young growth is usually hairy but these hairs disappear with age. Swelling of apical or primary growing point buds can occur from September onward and new growth or bud break is generally seen 3-4 weeks after this. It takes a further two weeks for the new leaf to unfold. However, lateral buds that grow off the side of an existing shoot generally take an extra two weeks to develop versus apical buds. Out of the five leaves produced by each shoot on a mature tree each season, the last leaf is usually the biggest. Old leaves of the plant are usually shed during this new growing season, with most old leaves having dropped by August.

In general, flowering occurs between late December and mid-February and fruiting occurs between April and June. However, the process of these two life cycles are more defined and can change due to factors such as temperature. Flowers come from auxiliary buds and are grouped into dense clusters with 1-3 clusters of flowers being produced by each apical shoot on a mature tree and 4-6 on a younger tree. This results in a high density of flowers which can cover most of the crown in a white/yellow colour as produced by the flowers. The flower head of each individual flower can overlap with another flower head which blankets the crown of the plant during summer. These flowers open in late December and usually shed petals by the end of February.

The seeds of Oleria ilicifolia are 2mm long and are attached to a 3mm long pappus (group of hairs). This pappus helps the seed to disperse through wind dispersal. The pappus acts as a parachute of hairs which slows the rate at which the seed falls, allowing the seed to fall for several seconds on a calm day. On a windy day, a seed falling from 6 meters high has the ability to travel a large distance to disperse.

Interactions
It is thought that Olearia ilicifolia are entomophilous or adapted specifically for interactions with insects surrounding Pollination. Knowledge to date suggests that pollination is carried out by insects and then the seeds are dispersed by wind.

It has been recorded that small beetles of the Dascillidae family and weevils of the Curculionidae family frequently visit the flowers of the mountain holly along with different native bees and flies. Two species of caterpillar feed on the leaves of mountain holly, with one eating young/growing leaves in October/November. The other, a caterpillar which has been recorded transitioning into a Geometrid moth, consumes adult leaves during summer. Plant lice and other unidentified species of moth have also been recorded feeding on the plants soft growing leaves. As a result of the spiny and stiff serrated leaf margins, this plant is not eaten by introduced mammals or other Omnivore s. Some insects lay their larvae on mountain molly, these larvae can feed on and damage the seeds produced by the plant, these seeds are unable to grow into shrubs or trees as a result.

Olearia ilicifolia is a plant species that thrive in a cool climate and is stressed under hot or humid conditions, which lead to fatality for the plant. Mountain holly like environments with high organic material, particularly humus-rich soils on a rocky margin that are well-drained and have high moisture content.

Further information
One interesting observation about Hakeke that has been made is that South Island plants tend to have wider leaves than their North Island counterparts. In fact, it is thought by some Botanists that the two populations are distinct enough to be separate species, although this has not been proved yet. Olearia ilicifolia can hybridize with Olearia lacunosa and Olearia arborescenes to form the hybrid species Olearia macrodonta.