Coprosma Species, Alpine Mirror Plant, Alpine Mirrorplant

Alpine Mirror Plant, Pilo, Mountain Mirror Plant (Coprosma montana) is an endemic Hawaiian Islands native plant. It can be found in suba...Read Morelpine shrublands where it is a dominant part of the vegetation, in subalpine woodlands and occasionally in mesic forests from 1830 to 3050m on East Maui and Hawai‘i (the Big Island). Haleakala; or East Maui Volcano is a massive shield volcano that forms more than 75% of the Hawaiian Island of Maui. Pilo is one of the of the commonest shrubs from Haleakala National Park Headquarters to 9,000 feet outside the crater.as well as throughout the crater. Pilo prefers acid and neutral soils and requires moist soil. It can grow in full sun or semi-shade as an understory plant at the edge of woodlands. The plant ranges in size from a small shrub up to a large shrub and small tree depending upon its habitat. In Kaupo Gap, it is a small tree up to 20 feet tall. I added many photos of Pilo and its habitats to emphasize its varying habits and its ability to grow in harsh environments.

Pilo has small, elliptical or lance-shaped, thick leaves below which is a pair of pointed, scale-like, 1/8 inch (3 mm) long triangular bracts (stipules) that have cilia on the upper borders. The stipules appear at ringed nodes. The leaves have short slender leaf-stalks which are less than 1/4 inch (6 mm) long. The leaves are dull green on the upper surfaces which have conspicuous nerves and paler underneath which allows the darker colored veining to be easily seen.

Pilo's greenish, inconspicuous about 1/4 inch (6 mm) long flowers are either male or female (dioecious); however, only one sex is to be found on any one plant. Thus, both male and female plants must be grown if seed is required. The flowers are are pollinated by wind. Female flowers have a short, 5–6 curved back lobes on the tubular corolla, a cup-shaped base (hypanthium) with calyx teeth and a pistil with a two-celled inferior ovary and two styles. The male flowers have as many stamens as corolla lobes which are attached near the base of the tube and extending beyond. The flowers are followed in the fall by fruits which are 1/4 inch (6 mm)in diameter round, shiny drupes. The drupes are light green when immature, turn bright yellow to dark orange or red and finally turn black as they mature. Each fruit contains 2 half-round nutlets.

One may wonder why pilo (Coprosma montana) is commonly called "mirror plant" when nothing about the plant is mirror-like. One explanation is that Coprosma repens, a larger coastal shrub native to New Zealand and introduced to the Hawaiian Islands, has highly smooth reflective leaves. It is commonly called "mirror plant". So, the name has been applied to other Coprosma species as well. Coprosma repens has become invasive in the Hawaiian Islands.