Lexington’s vacuum truck began collecting leaves this week. It’s the start of a collection period that runs into December. Since leaves don’t necessarily drop on a schedule, city Arborist Rob Allen says setting pick-up times can create a challenge. “We’re trying to impose kind of a calendar deadline on an organic issue. For example, this year we had a drought followed by some pretty cool early fall weather, well that affects the timing of when the leave drops off the tree,” said Allen.