Canarium ovatum

Description

The pili tree is an attractive symmetrically shaped evergreen, averaging 20 m (66 ft) tall with resinous wood and resistance to strong winds. It is dioecious, with flowers borne on cymose inflorescence at the leaf axils of young shoots. As in papaya and rambutan, functional hermaphrodites exist in pili. Pollination is by insects. Flowering of pili is frequent and fruits ripen through a prolonged period of time. The ovary contains three locules, each with two ovules, most of the time only one ovule develops (Chandler 1958).

The pili fruit is a drupe, 4 to 7 cm (1.6 to 2.8 in) long, 2.3 to 3.8 cm (0.91 to 1.50 in) in diameter, and weighs 15.7 to 45.7 g (0.035 to 0.101 lb). The skin (exocarp) is smooth, thin, shiny, and turns purplish black when the fruit ripens; the pulp (mesocarp) is fibrous, fleshy, and greenish yellow in color, and the hard shell (endocarp) within protects a normally dicotyledonous embryo. The basal end of the shell (endocarp) is pointed and the apical end is more or less blunt; between the seed and the hard shell (endocarp) is a thin, brownish, fibrous seed coat developed from the inner layer of the endocarp. This thin coat usually adheres tightly to the shell and/or the seed. Much of the kernel weight is made up of the cotyledons, which are about 4.1 to 16.6% of the whole fruit; it is composed of approximately 8% carbohydrate, 11.5 to 13.9% protein, and 70% fat. Kernels from some trees may be bitter, fibrous or have a turpentine odor.

Distribution and habitat

Pili is native to regions which includes maritime Southeast Asia (Indonesia, Malaysia, and the Philippines), Papua New Guinea, and Northern Australia.

Pili is a tropical tree preferring deep, fertile, well drained soil, warm temperatures, and well distributed rainfall. It can not tolerate the slightest frost or low temperature. Refrigeration of seeds at 4 to 13 °C (39 to 55 °F) resulted in loss of viability after 5 days. Seed germination is highly recalcitrant, reduced from 98 to 19% after 12 weeks of storage at room temperature; seeds stored for more than 137 days did not germinate. Asexual propagations using marcotting, budding, and grafting were too inconsistent to be used in commercial production. Young shoots of pili were believed to have functional internal phloems, which rendered bark ringing ineffective as a way of building up carbohydrate levels in the wood. Success in marcottage may be cultivar dependent. Production standards for a mature pili tree is between 100 to 150 kg (220 to 330 lb) of in-shell nut with the harvest season from May to October and peaking between June and August. There are high variations in kernel qualities and production between seedling trees.

Most pili kernels tend to stick to the shell when fresh, but come off easily after being dried to 3 to 5% moisture (30 °C (86 °F) for 27 to 28 h). Shelled nuts, with a moisture content of 2.5 to 4.6%, can be stored in the shade for one year without deterioration of quality (Coronel et al. 1983).

Cultivation and uses

Although they are grown as ornamental trees in many areas of the Old World tropics of Indonesia, Malaysia and the Philippines, only the Philippines produces and processes pili nuts commercially. Production centers are located in the Bicol region, provinces of Sorsogon, Albay, and Camarines Sur, southern Tagalog, and eastern Visaya. There is no commercial planting of this crop, fruits are collected from natural stands in the mountains near these provinces. In 1977, the Philippines exported approximately 3.8 t of pili preparation to Guam and Australia.

The most important product from pili is the kernel. When raw, it resembles the flavor of roasted pumpkin seed, and when roasted, its nutty flavor and waxy texture is similar to the pine nut.

In the Philippines, pili is used in candies and brittle.

In Indonesia, especially in Minahasa and Moluccas islands, the kernels are used for making cake, bobengka in Minahasan or bubengka in Maluku. Pili kernel is also used in chocolate, ice cream, and baked goods. The largest buyers of pili nuts are in Hong Kong and Taiwan, the kernel is one of the major ingredients in one type of the famous Chinese festive desserts known as the "moon cake".

Nutritionally, the kernel is high in manganese, calcium, phosphorus, and potassium, and rich in fats and protein. It yields a light yellowish oil, mainly of glycerides of oleic (44.4 to 59.6%) and palmitic acids (32.6 to 38.2%).

The young shoots and the fruit pulp are edible. The shoots are used in salads, and the pulp is eaten after it is boiled and seasoned. Boiled pili pulp resembles the sweet potato in texture, it is oily (about 12%) and is considered to have food value similar to the avocado. Pulp oil can be extracted and used for cooking or as a substitute for cotton seed oil in the manufacture of soap and edible products. The stony shells are excellent as fuel or as porous, inert growth medium for orchids and anthurium.

The tree's sap is also used for igniting fire,substituting gasolines.

Future prospects

According to Richard A. Hamilton, University of Hawaii at Manoa, the current status of the pili is equivalent to that of the macadamia some 30 years ago. It has great potential to develop into a major industry.

The immediate concern in pili production is the difficulty of propagation. The lack of an effective clonal propagation method not only hampers the collection of superior germplasm but also makes it almost impossible to conduct feasibility trials of this crop. Pili cultivars such as 'Red', 'Albay', and 'Katutubo' were selected in the Philippines. The National Clonal Germplasm Repository at Hilo, USDA-ARS, has initiated studies of in vitro and vegetative propagation for the multiplication and long-term preservation of pili. A recently released pili cultivar in Hawaii, 'Poamoho', may further stimulate the interest in this crop. Besides the desirable production and quality attributes, its kernels separate easily from the hard shell without the need of prior drying (30 °C (86 °F) for 27 to 28 hours. This is an important cost saving feature for processing.