Acronychia acidula, commonly known as lemon aspen, is a species of rainforest tree native to eastern Australia. It belongs to the Rutaceae family, which also includes citrus plants, and shares some characteristics with its more familiar relatives. This tree is recognized for its attractive foliage and its distinctive, aromatic fruit. The growth habit of Acronychia acidula is that of a small to medium-sized tree, typically reaching heights of 8 to 15 meters, though it can occasionally grow taller in optimal conditions. Its canopy is generally dense and rounded. The leaves are compound, arranged oppositely along the stem, and are usually trifoliate, meaning each leaf is divided into three leaflets. The leaflets are ovate to elliptic in shape, with smooth margins and a glossy, dark green upper surface. A notable feature of the leaves is their strong lemon scent when crushed, a characteristic that contributes to the common name. The bark is usually smooth and greyish, becoming slightly rougher with age. Flowering occurs from late spring through summer, producing clusters of small, star-shaped flowers. These flowers are typically white or cream-colored and possess a sweet fragrance, which can attract pollinators. Following successful pollination, the tree develops its characteristic fruit. The fruits are drupes, roughly spherical, and measure about 1.5 to 2.5 centimeters in diameter. They are initially green and mature to a pale yellow or creamy white color. The flesh of the fruit is translucent and contains a few small seeds. The fruit is known for its intensely sour, acidic flavor, with a distinct citrusy aroma, hence the common name "lemon aspen." Acronychia acidula is found in subtropical and warm temperate rainforests, often growing in moist, well-drained soils in areas with good rainfall. Its natural distribution extends along the coastal regions of Queensland and New South Wales. While it is a rainforest species, it can adapt to cultivation in a range of environments, provided it receives adequate moisture and protection from frost, especially when young. It is considered moderately hardy and can be grown as an ornamental tree in suitable climates. The fruit of Acronychia acidula has garnered interest for its culinary potential. Its intense acidity and strong lemon-like flavor make it a unique ingredient for jams, jellies, sauces, and beverages, often used in small quantities to impart a sharp, citrusy note. The aromatic properties of its leaves and fruit are also noteworthy. Ecologically, the tree provides habitat and food sources for various native fauna. The scientific name *Acronychia* is derived from Greek words referring to the pointed tips of the petals, a characteristic of some species within the genus. The specific epithet *acidula* refers to the acidic nature of its fruit.