Let's work through what we can and cannot know if M is placed in lot 2.
We know from the rules that M and W cannot be in the same plot, so we know that W cannot be in lot 2.
We also know from the rules that either M or O BUT NOT both will be placed in lot 2. So we can say for sure that since M is in lot 2, O is not in lot 2.
Because O is not in lot 2, H is also not in lot 2 because H and O must appear together.
O and H can also not be in lot 1 because we known they must appear with a third tree. But in order to satisfy the last rule, lot 1 cannot have more than 2 trees.
Since O and H cannot be in lots 1 or 2, we know they must be in lot 3 with one other tree.
So here is a summary of what we do know:
Lot 1: L OR W Lot 2: M Lot 3: O, H, and one more tree
As you can see, L, W S and P remain unaccounted for.
Hope this helps! Let me know if you have any more questions