A Venus flytrap counts how many times it's been touched before deciding to close

Trigger hairs inside the trap fire an electrical signal when brushed, but the trap only snaps shut if a second touch arrives within about 30 seconds of the first. A 2020 study found the plant tracks this using a build-up of calcium inside its cells, and keeps counting afterward: enough touches and it starts producing digestive enzymes.

— Mitsuhiro Iwasaki et al., University of Würzburg, The Venus Flytrap Dionaea muscipula Counts Prey-Induced Action Potentials to Induce Sodium Uptake — Current Biology, 2020