Questions & Answers about Wanneer die aartappels gaar is, kan ons eet.
Because wanneer introduces a subordinate clause in Afrikaans. In subordinate clauses, the finite verb often moves to the end.
So:
Compare that with a main clause:
- Die aartappels is gaar = The potatoes are cooked
This verb-final pattern after words like wanneer is very common in Afrikaans.