Depending upon climate and soil type the tree may grow to over 30 metres (100 ft)[7] in height, but it typically stands 9–12 m (30–40 ft) in height and the crown is round.[3][8] The trunk is 80 cm (2+1⁄2 ft) thick[3] with corky bark.[8] The branches are long and thick, typically drooping.[3]

The leaves are oblong and blunt-tipped, usually 10–20 centimetres (4–8 in) long and 5 cm (2 in) wide.[3] The leaves are pinnately compounded and alternate.[8] There are 6 to 9 pairs of leaflets per leaf[8] and the upper surface is wavy and a dark, glossy-green.[3]

The longan tree produces light-yellow inflorescences at the end of branches.[3] The inflorescence is commonly called a panicle; they can be 10–46 cm (4–18 in) long, and widely branched.[8] The small flowers have 5 to 6 sepals and brownish-yellow petals.[8] The flower has a two-lobed pistil and 8 stamen. There are three flower types, distributed throughout the panicle;[3] staminate (functionally male), pistillate (functionally female), and hermaphroditic flowers.[8] Flowering occurs as a progression.[8]

The fruit are spherical and about 2.5 cm (1 in) wide; they hang in drooping clusters. The shell is tan, thin, and leathery with tiny hairs;[8] when firm, it can be squeezed (as in the cracking of a sunflower seed) to shell the fruit.[citation needed] The flesh is translucent, and the seed is large and black with a circular white spot at the base.[3][8] This gives the illusion of an eye.[3] The flesh has a musky, sweet taste, which can be compared to the flavor of lychee fruit.[3] The seed is round, hard, and has a lacquered appearance.[citation needed]

The longan tree is somewhat sensitive to frost. While the species prefers temperatures that do not typically fall below 4.5 °C (40 °F), it can withstand brief temperature drops to about −2 °C (28 °F).[9] Longan trees prefer sandy soil with mild levels of acidity and organic matter.[3] Longans usually bear fruit slightly later than lychees.[10]