Fruits often hold surprises in how they develop. While many fruits grow in familiar ways, some exhibit unique patterns. Understanding these different growth habits reveals the diverse strategies plants use to produce and disperse their seeds.
The Cashew: A Prime Example
The cashew tree (Anacardium occidentale), native to northeastern Brazil, is a tropical evergreen known for its distinctive fruiting structure. It produces two main parts that appear together: a fleshy, brightly colored “cashew apple” and a kidney-shaped “cashew nut” attached to its end. The cashew apple, which can be yellow or red, develops from the flower’s pedicel and receptacle. It grows 5–11 cm long and is notably larger than the true fruit.
This vibrant cashew apple hangs from the tree, with the grayish-brown cashew nut visibly attached at its lower tip. The nut, about 2.5 centimeters long, is encased in a double-layered shell. This arrangement, with the smaller nut dangling from the larger apple, creates the impression that the nut grows “upside down” from its fruit.
Understanding True Fruits and Accessory Fruits
In botany, a “true fruit” develops exclusively from a flower’s ripened ovary after fertilization. Other floral parts typically degenerate. Examples include cherries, plums, and mangoes, where the edible portion originates solely from the mature ovary.
In contrast, an “accessory fruit” (also known as a pseudofruit or false fruit) incorporates other plant tissues, such as the receptacle, pedicel, or calyx, in addition to the ovary. Common examples include strawberries, where the fleshy part comes from the enlarged receptacle, and apples, where the hypanthium forms much of the edible flesh.
Why the Cashew Appears “Upside Down”
The unique appearance of the cashew fruit is a direct result of its botanical classification. The “cashew apple” is not a true fruit; it is an accessory fruit. This fleshy, colorful part develops from the swollen pedicel and receptacle of the cashew flower.
The true fruit of the cashew tree is the kidney-shaped “cashew nut” that grows at the end of the cashew apple. This nut is botanically a drupe, a fruit with a fleshy exterior and a single, hard-shelled seed inside. The true fruit (nut) develops first, then the pedicel expands to form the large cashew apple, creating the visual phenomenon of the nut appearing to hang “upside down” from the apple.