Pseudowintera axillaris

Pseudowintera axillaris is one of four Winteraceae species endemic to New Zealand.

It has many distinguishing features that can identify it from other Winteraceae species.^[2] Growing up to 8 metres tall and a trunk up to 10 cm in diameter^[3] this small shrub-like tree, prefers damper, cold, tree shaded locations found in New Zealand forests in the North Island and the northern parts of the South Island.^[4] Distinguishing features of this plant include its dark green coloured leaves, and natural glossy wax that gives the underside a pale to glaucous but not white; midvein pale appearance. These leaves have smooth margins and unlike many other plant species, P. axillaris usually has no red or brown blotches or discolouration.^[5] Adult leaves can grow up to 6–10 cm long by 3–6 cm wide^[6] and have red leaf stalks, with yellowish midribs, and smooth margins.^[7][2] Juvenile leaves have distinctive, white, net-like secondary veins on the upper surface. Another known feature of the P. axillaris is the peppery taste it upholds when chewing. P. colorata is known for its extremely spicy peppery taste compared to that of a chilly, whereas P. axillaris has a slight, pleasant peppery taste, known to keep plant grazing insects away.^[8] P. axillaris has very dark red – black branches, with the branchlets usually becoming more black in colour toward the leaves. It is considered to be a very primitive flowering plant, and is one of the more common of the four Pseudowintera species, after P. colorata.^[2] The flowers are small in size, 10mm across,^[9] [bisexual]^[7] on quite long stalks, and greenish yellow in colour.^[2] They occur in clusters in the leaf axils or in the scars of fallen leaves. Petal numbers vary between 4-7 free petals,^[2][7] and calyx cup shaped.^[3] The petals are 5-6mm long, narrow-oblong to narrow-obovate, apex obtuse.^[7] Other parts of the flower are symmetrical^[2] apex obtuse, carpels 1–6, stigma apical^[7] very short stamens but many (6-20)^[7] crowded around a few short ovaries^[2] Pseudowintera axillaris fruits are berries, one from each ovary^[2] producing a 3-6-seeded fleshy globose to subglobose berry 5-6mm in diameter^[7] orange to red when ripe.^[2]

Pseudowintera axillaris is endemic to New Zealand.^[2] Included within the family of Winteraceae where many of these plant species are found in Southern North America, and temperate Asia.^[3]

Pseudowintera axillaris is commonly found in both the North and South Island, in Lowland and lower montane forests. From Kaitaia in the north down to the Marlborough sounds and the north west of the South Island.^[2] They are quite popular just South of Auckland, Specifically in the Waitakere region, and within the Northern parts of the South Island.^[4] P. colorata and P. axillaris are very similar in nature and are often found within the same locations and are quite common throughout New Zealand. They can live in unison with each other as competition is eliminated where P. axillaris prefers shaded, damp areas, and is often more present within lowland montane forests, whereas P. colorata prefers areas of higher light and are more frequent around the edges of these forests. They are highly adapted to their particular niche.

The lowland horopito favours colder and more shaded environments, where taller more invasive trees grow and provide a vegetative cover. New Zealand forests are known for their rich, nutrient dense soils, so P. axillaris has adapted to survive in conditions where this nutrient dense soil is present. The underlying factor here is that P. axillaris thrives where other taller plants flourish. This is due to the fact branches, leaves and twigs fall off these bigger trees and contribute to the nutrients of the soil below, creating a humus layer. The Humus layer is dark organic material that forms in soil as a result of decaying plants and even animals. This provides a stable and strong nutrient base for P. axillaris to thrive and also offers a stable water supply where the shade offers dampness.

Flowers occur as auxiliary fascicles from spring (September) to early summer (December) and fruits ripen to red from late spring (October till January), persisting on the plant through till winter (June).^[9][2] The P. axillaris remains relatively still through the January and February months as seen on the phenology graph.^[10] In a study of the reproductive ecology of the Pseudowintera axillaris it was found that this plant has a pollination system liable to change, relying on the transferral of pollen by Thrips obscuratus and small flies, as well as pollen being carried by wind.^[11] Pseudowintera axillaris flowers remain on the plant for 7–11 days and the stigmatic crests are responsive in the course of early anthesis, secreting a small supply of nectar, during the last days of flowering the anthers shed pollen. When a thrips has finished feeding on one flower it will crawl to the next, this usually being in the same inflorescence or the same branch, by this system both early anthesis flowers holding nectar and late anthesis flowers containing pollen are visited.^[11] These insect visits are few, and isolated plants bear very few fruits, along with low numbers of seed in each fruit.^[12] Along with the entire genus Pseudowintera, Pseudowintera axillaris models high rates of self‐sterility which appears to take place uniformly at the zygotic stage of embryogeny.^[13]