Bev, there are no silly questions in gardening, the flower head is the seed box for the plant and when it sets seed it gives up, job done. We nip the head off to keep it up to speed doing its job for us producing more flowers.
The answer is keep nipping the dead flowers off and the plant will keep doing its stuff.
I suppose to young gardeners us elderly know Al's do come across as a bit comical, the thing is even at my age well past retirement we are still learning from each other, we all have our own methods so at times it can sound a bit like a world war as we argue it out, we are harmless though.
Frank.