Trees of Canarium ovatum are attractive symmetrically shaped evergreens, averaging 20 m tall with resinous wood and resistance to strong wind. C. ovatum 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).
Pili fruit is a drupe, 4 to 7 cm long, 2.3 to 3.8 cm in diameter, and weighs 15.7 to 45.7 g. 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.
Although they are grown as ornamental trees in many areas of the Old World tropics of 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.
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 °C to 13 °C 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 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 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).
The most important product from pili is the kernel. When raw, it resembles the flavor of roasted pumpkin seed, and when roasted, its mild, nutty flavor and tender-crispy texture is superior to that of the almond. 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 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.