Mount Mawson Pine (Pherosphaera hookeriana)

Pherosphaera hookeriana, or Mount Mawson pine (syn. Microstrobos niphophilus), is a dwarf conifer endemic to Tasmania. It is most commonly found at altitudes above 600 meters in the southwest and central high country. There are roughly 30 known sites, with population numbers in the tens of thousands. The species occurs in various habitats, typically near water bodies, mainly on dolerite-derived (volcanic) soils. The species is susceptible to fire and disturbances and is vulnerable to extinction from climate change. This paleoendemic Tasmanian conifer is one of only two species in the genus Pherosphaera, with Pherosphaera fitzgeraldii (syn. Microstrobos fitzgeraldii) restricted to the Blue Mountains in New South Wales.

Tree Height and Spread: Pherosphaera hookeriana is a slow-growing shrub that typically reaches a height of 1 to 1.5 metres and a spread of 1.5 metres. Wild populations have been observed up to 5 metres tall and may form extensive clonal colonies via vegetative growth. Various factors, such as environmental conditions and soil quality, will influence the plant’s growth rate.

Preferred Soil Type and pH: Pherosphaera hookeriana prefers well-drained, lightly acidic soil. It thrives in dolomite and ultramafic soils, which are magnesium-rich, calcium, potassium and phosphorus-poor soils developed on regolith-derived rock deposits from previous ice ages. It does best in a pH range of 5.5 to 7 in a high-quality Australian potting mix with good drainage. Ensuring the soil retains moisture without becoming waterlogged is essential, as excessive moisture can lead to root rot.

Climate and Environmental Requirements: Pherosphaera hookeriana is adapted to cool and moist conditions. It grows best in cool temperate climates and high-altitude regions. It can tolerate frost and prefers areas with high humidity. This species prefers a consistent and even moisture supply and may struggle in hot and dry climates.

Light Requirements: Pherosphaera hookeriana prefers full sun to partial shade. While it can tolerate some shade, it tends to grow more compact and dense in full sun. Ensuring the plant receives adequate light for the best results is essential.

Watering and Fertilising: Pherosphaera hookeriana requires regular watering, particularly during dry periods. It prefers lightly moist soil but can suffer from root rot if it becomes waterlogged. A thin layer of organic mulch or composted pine bark around the base can help retain moisture and regulate soil temperature. Fertiliser application is generally unnecessary; however, if applying, ensure it is low or does not contain phosphorus.

Pruning and Maintenance: Pherosphaera hookeriana requires minimal pruning. However, removing any dead or damaged branches is essential to maintain the tree’s health and aesthetic appeal. Regular inspection for pests or diseases is recommended, although this species is generally considered resistant to significant pest issues.

Uses: Pherosphaera hookeriana is primarily grown for its ornamental value. Its shrub form and dark green foliage make it an attractive addition to gardens and landscapes, particularly in cooler regions. It is often used as a specimen shrub and is highly ornamental and collectable.

Pherosphaera hookeriana is a slow-growing coniferous shrub that prefers cool and moist conditions. It requires well-drained, lightly acidic soils, full sun to partial shade, and regular watering to maintain health and appearance. With its compact habit and dark green foliage, it adds a touch of uniqueness and beauty to garden landscapes, particularly in cooler regions.