I was reading this sentence and thought it ambiguous:
The trees must have grown since he died because they were no longer young when I first saw them.
This could mean:
1) The trees were already old when I first saw them.
2) The trees were not as young as when I first saw them.
Option 1 seems to be obviously grammatically correct one. The reason I thought option 2 might be correct is because of the logical coherence between the two causes connected by "because"--the trees have grown because they were young last time but they are not young at the moment, hence the grown.
This might seem a rather minute question, but I would really appreciate your clarification. Thanks!