油柑子一般高約1至3米，生長於灌叢或疏林中。花期為4至6月而果期為7至9月。花小而黃綠色，在枝條上簇生，果實球形，直徑約1.5釐米。葉片兩列排，羽狀複葉，葉線狀長圓形，頂端鈍圓或截平，有銳尖頭或微凹，基部淺心形而稍偏斜，上面綠色，下面淺綠色，長0.8-2釐米，寬2-6毫米，乾後淺褐色或帶紅色，近無柄；落葉時整個小枝脫落；託葉線狀披針形，長1.2-2.5毫米，褐紅色，邊緣有睫毛。花簇生於葉腋，花小，黃色；單性，雌雄同株，具短柄；每花簇有1朵雌花，花梗長0.5毫米，花盤杯狀，包藏子房達一半以上，邊緣撕裂，每花有花萼5-6片，長圓形或匙形，較厚，邊緣膜質，多少具齒無瓣，子房卵圓形，子房上位，3室，花柱3，基部合生，頂端再2裂；雄花雄蕊3，花絲合生成0.3-0.7毫米的柱，花藥直立，長圓形，頂端具短尖頭。蒴果呈核果狀，圓球形，直徑約1.5釐米，外果皮肉質，淺綠色，初為黃綠色，成熟後呈赤紅色，內果皮硬殼質；種子略帶紅色。花期4-6月，果期7-9月。
Mandarin oranges are generally about 1 to 3 metres tall and grow in shrubs or open forests. The flowering period is from April to June, and the fruiting period is from July to September. The flowers are small and yellowish-green, clustered on the branches, and the fruits are spherical, about 1.5 cm in diameter. Leaves in two rows, pinnate compound leaves, linear oblong, apex obtuse or truncated, with acute pointed or slightly concave, base shallow heart-shaped and slightly oblique, green above, light green below, 0.8-2 cm long, 2-6 angular meters wide, light brown or reddish after drying, nearly sessile; the whole branchlet falls off when defoliating; the leaves are linear-lanceolate, 1.2-2.5 mm long, maroon-red, margins with eyelashes. Flower clusters born in leaf axils, flowers small, yellow, unisexual, dioecious and plant, with short stalks; each flower cluster has 1 female flower, peduncle 0.5 mm long, flower disc cup-shaped, containing more than half of the oary, edge torn, each flower has 5-6 petals, oblong or key-shaped, thick, margins membranous, more or less toothed without petals, ovary ovate, ovary superior, 3 chambers, columella 3, base connate, apex 2-lobed, male flower stamens 3, filaments synthesized to form a column of 0.3-0.7 mm, anthers erect, oblong, apex with a short pointed tip. The pods are drupe-shaped, spherical, about 1.5 cm in diameter, the exocarp is fleshy, light green, yellow-green at first, reddish when ripe, the endocarp is hard chitinous, and the seeds are slightly reddish. The flowering period is from April to June, and the fruiting period is from July to September.