Cordia subcordata is a species of flowering tree in the borage family. It can be found growing in eastern Africa, South Asia, Southeast Asia, northern Australia and the Pacific Islands including Hawaii. The plant is known by a variety of names, including kou, beach cordia, sea trumpet, and kerosene wood, among others.
Other names for the species include kanawa, tou, mareer, manjak, snottygobbles, glueberry, and narrow-leafed bird lime tree. In Java and Madura, it is known as kalimasada, purnamasada, or pramasada; Javanese folklore considers the tree to contain spiritual power.[1] In the Marshall Islands it is known as kono.[2] In Fiji, it is called nawanawa.
This species has a very wide range from the east coast of Africa east throughout tropical Asia and Oceania, as far as Hawaii. This distribution arose from the special characteristics of its fruit, which allowed successful oceanic dispersal.[3] Prior to 2001, C. subcordata was considered to be a Polynesian introduction to Hawaii by many authorities, but subfossil evidence from Makauwahi Cave in Kauai indicates that it was an abundant species in Hawaiian lowland forests well before humans arrived, confirming its status as an indigenous species.[4]
C. subcordata or kou trees are found along coasts at elevations from sea level to 30m (100feet) that receive 1000- of annual rainfall. They prefer neutral to alkaline soils (pH of 6.1 to 7.4), such as those originating from basalt, limestone, clay, or sand. Allowable soil textures include sand, sandy loam, loam, sandy clay loam, sandy clay, clay loam, and clay. It can also grow on the margins of rocky shores and mangrove swamps.
A mature kou tree grows to 7- at maturity, but may be as tall as 15m (49feet). It has ovate leaves that are 8- and 5- wide with short hairs on the upper surface.[5]
Blooming occurs throughout the year, but most kou flowers are produced in the spring. Each kou flower is funnel- or tube-shaped 1- long and 0.4- in diameter, made of orange petals and pale green sepals that form cymes or panicles.[6]
Kou trees produce fruit all year around. Their fruit are spherical 2- long, brown, and woody when mature. Each fruit contains four or fewer seeds that are 10- long. The fruit are buoyant and may be carried very far by ocean currents.
The seeds are edible and have been eaten during famine.
The wood of the tree has a specific gravity of 0.45, is soft, durable, easily worked,[7] and resistant to termites. In ancient Hawaiʻi kou wood was used to make ʻumeke (bowls), utensils, and ʻumeke lāʻau (large calabashes) because it did not impart a foul taste to food. ʻUmeke lāʻau were 8–16 litres (2–4 gal) and used to store and ferment poi. Kou wood burns readily as firewood, and this led to the nickname of "kerosene tree" in Papua New Guinea. The flowers were used to make lei, while a dye for kapa cloth and aho (fishing lines) was derived from the leaves. Fijians obtain fibre to make baskets and garlands from its inner bark by soaking it in seawater.[8]
In the western Solomon Islands, in Vanuatu, on Waya Island, and in Tonga, it is used for carving. On New Ireland, its wood is always used for the ceremonial entrances to men's houses.[9]
Despite its very wide distribution, this species faces threats in parts of its range. During the late 19th century, herbivory by the kou moth (Ethmia nigroapicella) nearly extirpated this species on the Hawaiian Islands.[10] It is thought to be highly endangered in Sri Lanka, only persisting at a small number of sites that are under pressure from development. Logging of mature trees to create carvings for the tourism industry is also thought to be a threat throughout much of Papuasia. In addition, it may potentially be threatened by storms and sea level rise.