Given the task definition and input, reply with output. In this task, you're given the title of a five-sentence story and the first four sentences. Your job is to write the last sentence of the story such that it seamlessly connects with the rest of the story.

Title: Trees. Sentence 1: Ben needed to plant trees in his yard. Sentence 2: He picked out trees based on climate and location around the house. Sentence 3: He spent all day planting the trees. Sentence 4: He had to water them for years and years.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
After many long years, they finally grew big and tall.