This autumn, you may notice an unusually large number of acorns scattered under every oak tree. This isn’t a figment of your imagination; it’s a natural occurrence known as a mast year, and it’s currently taking place across the UK.

A mast year is a biological event in which certain tree species, notably oaks and beeches, produce a significantly larger crop of seeds in unison. It’s not just a minor increase; during a mast year, an oak tree can shed thousands, sometimes tens of thousands, more acorns than usual.

These abundant harvests are followed by years of much lower, or even negligible, acorn production. This fluctuation is a smart and ancient evolutionary tactic.