Port Arthur Plum (Cenarrhenes nitida)

Cenarrhenes nitida, known as the Port Arthur Plum, is a monotypic species of flowering plant in the Proteaceae family, endemic to southern and western Tasmania. It is commonly known as the Port Arthur Plum or Naitve Plum and is a medium-sized shrub to small tree that can grow up to 10 meters tall, although it is often smaller in cultivation. It is an uncommon ornamental plant on the mainland and popular in Tasmanian gardens due to its attractive foliage, fruit and flowers. Expect heights between 2 to 3 metres and a spread of 2 metres in most cultivated garden settings.

The leaves of Cenarrhenes nitida are shiny and green with a leathery texture. Its leaves, roughly 8 to 12 cm long, are thick, dull and hairless with a cleanly serrated edge and rounded tip. These are attached to the stem via a short stalk. When crushed, the leaves and branchlets have a nauseating stale cabbage smell which helps distinguish them from the similar-looking Anopterus glandulosus.

The fruit of Cenarrhenes nitida is a fleshy drupe that closely resembles commercial plums from the genus Prunus. The fruit is roughly 1.5 cm in size and can get up to 3 cm. The fruit is smooth, with deep purple skin, is edible with a chalky-tasting pink-white flesh and a large stone at the centre. Much like plums, the fruit has a groove running down one side of the fruit and a fine dusty layer on the skin, giving it a bluish colour that is easily removed by rubbing. Fruit ripens in autumn from March to May.

Cenarrhenes nitida occurs most often as an understory tree or small shrub in wet sclerophyll forests and cool temperate rainforests with poor soils. Occasionally, in heathland, button grass sedges land and scrub. It prefers well-drained soil that is slightly acidic to neutral, with a pH range of 5.5 to 7.5. It can tolerate a range of soil types, including sand, loam, and clay, but it does not like wet or poorly drained soils. The plant prefers a sunny to partially shaded position, although it can tolerate some shade. It is drought-tolerant once established but will benefit from regular watering during dry periods.

Propagation of Cenarrhenes nitida can be achieved by seed or cuttings. Seeds can be sown in autumn or winter, while cuttings can be taken in late summer to early autumn. It is often difficult to propagate and can grow very slowly if conditions are not right. They are best grown from seed as cuttings will remain green for a long time without developing roots before turning brown.

Cenarrhenes nitida does not require regular pruning, although removing damaged or diseased branches may be necessary. The plant is generally low-maintenance and does not require fertilizer, although it will benefit from a slow-release, zero-phosphorus fertilizer in spring.

One potential issue with Cenarrhenes nitida is that it is susceptible to root rot in poorly drained soils. To avoid this, it is essential to ensure the ground is well-draining and to avoid over-watering. Pests and diseases are generally not a significant issue for Cenarrhenes nitida, although it may be susceptible to scale insects and borers.

Cenarrhenes nitida is a beautiful, relatively low-maintenance shrub to small tree well-suited to cool temperate gardens with well-composted and organic soil. Its attractive foliage and unique flowers make it a popular choice for gardeners looking to add colour and interest.