The fruit is contained in a spiny (very sharp) cupule 5–11 cm in diameter, also called "bur" or "burr".
The burrs are often paired or clustered on the branch and contain one to seven nuts according to the different species, varieties, and cultivars.
Around the time the fruits reach maturity, the burrs turn yellow-brown and split open in two or four sections. They can remain on the tree longer than they hold the fruit, but more often achieve complete opening and release the fruits only after having fallen on the ground; opening is partly due to soil humidity.