Symbol Analysis
Moss, weeds, and unkempt bits of nature invade the farmhouse at every turn. Overgrown nature imagery is one clue that no one has attempted to make things nice around here in a long, long time.
In the first stanza, the walls are rotting due to heavy moss and rust. It doesn't even seem like the walls are going to hold. Weeds have overgrown the latch to the gate, too:
Unlifted was the clinking latch;
Weeded and worn the ancient thatch
Upon the lonely moated grange. (6-8)
Clearly, no one has tried to get inside or outside in quite a while.
Tennyson uses nature in disrepair to signal to the reader that something isn't quite right with whoever is living in the farmhouse. And when we finally meet Mariana, we can see that the state of her farmhouse is also the state of her mind: overgrown with neglect and despair.