What does Mrs. Dubose do to anger Jem and Scout? What does Jem do in response, and how is he punished?

Mrs. Dubose makes unappropriate remarks about Atticus.

“Yes indeed, what has this world come to when a Finch goes against his raising? I’ll tell you!” She put her hand to her mouth. When she drew it away, it trailed a long silver thread of saliva. “Your father’s no better than the niggers and trash he works for!”

In response, Jem destroyed Mrs. Dubose's beloved camelias.

We had just come to her gate when Jem snatched my baton and ran flailing wildly up the steps into Mrs. Dubose’s front yard, forgetting everything Atticus had said, forgetting that she packed a pistol under her shawls, forgetting that if Mrs. Dubose missed, her girl Jessie probably wouldn’t.

He did not begin to calm down until he had cut the tops off every camellia bush Mrs. Dubose owned, until the ground was littered with green buds and leaves.

Jem's punishment is to spend every afternoon reading to Mrs. Dubose for one month.