Dacrydium cupressinum

Dacrydium cupressinum, commonly known as rimu, is a large evergreen coniferous tree endemic to the forests of New Zealand. It is a member of the southern conifer group, the podocarps.

The Māori name rimu comes from the Polynesian term limu which the tree's foliage were reminded of, ultimately from Proto-Austronesian *limut meaning "moss". The former name "red pine" has fallen out of common use.

Description
Rimu is a coniferous tree with dark red wood that reaches a height of 35–60 m, with a trunk 1.5–2 m in diameter. The bark is flaky and dark-brown in colour. In its juvenile stages the branches are thin and numerous, but as the tree grows older around three quarters of the tree becomes branchless. It has a lifespan of 600–800 years, but may reach beyond 1000 in rare cases.

The yellowish-green foliage varies in size and shape between the juvenile, sub-adult, and adult life stages. The leaves begin 0.4–10 mm long and 0.5–0.1 mm wide with sharp points. They are divided along an axis and roughly shaped like a sickle. In sub-adults the leaves shorten to 4–6 mm long, curve upward, and become diamond shaped. In adults the leaves become smaller, just 2–3 mm long, and press against one-another tightly.

Male and female cones, or strobili, appear first in sub-adults but on different male and female trees. Male cones are 5–10 mm long, rectangular shaped, and covered in a yellow pollen. Ovules appear on their own on upturning branchlets. The fruit consists of a 1–2 mm long fleshy orange receptacle and a 3–4 mm long dark brown rectangular-shaped seed. Rimu is distinctive enough that it is unlikely to be misidentified except as a seedling with Manoao colensoi, which have glossier, less fine leaves. It has a diploid chromosome count of 20.

Distribution
Rimu grows throughout New Zealand, in the North Island, South Island and Stewart Island/Rakiura. This species is common in lowland and montane forest. Although the largest concentration of trees is now found on the West Coast of the South Island, the biggest trees tend to be in mixed podocarp forest near Taupō (e.g., Pureora, Waihaha, and Whirinaki Forests). A typical North Island habitat is in the Hamilton Ecological District, where Fuscospora truncata and rimu form the overstory. Associate ferns on the forest floor are Blechnum discolor, Blechnum filiforme, Asplenium flaccidum and Hymenophyllum demissum. An 800-year-old rimu tree can be seen at the Otari-Wilton's Bush in Wellington.

Uses
Māori originally used the resinous heartwood of rimu (called māpara or kāpara) for wooden items such as heru (combs) and fernroot beaters. Historically, rimu and other native trees such as kauri, mataī and tōtara were the main sources of wood for New Zealand, including furniture and house construction. However, many of New Zealand's original stands of rimu have been destroyed, and recent government policies forbid the felling of rimu in public forests, though allowing limited logging on private land. Pinus radiata has now replaced rimu in most industries, although rimu remains popular for the production of high quality wooden furniture. There is also limited recovery of stump and root wood, from trees felled many years before, for use in making bowls and other wood turned objects.

The inner bark can also be used to treat burns and cuts.

In cultivation
Although slow to establish, with a long juvenile period and fairly high moisture requirements, rimu is widely grown as an ornamental tree in New Zealand. It is attractive at all growth stages, usually quite narrow when young, then developing into a broader tree with weeping branches before finally progressing to its more upright adult form. While rimu does exhibit some variation in the wild, garden cultivars are largely unknown, except for one recent introduction, 'Charisma', which is a compact, golden-foliaged form.

Pests and diseases
This species plays host to the New Zealand endemic beetle Agapanthida pulchella.