Recently, I discovered metaphor trees. I explained them as such: When you are constructing a novel, you should keep all your metaphors connected within the same field.
So for example, space is related to rocks and astronauts, but its different from birds, flowers, and air.
Or as one Twitter user described to me:
It’s when you start with a big solid metaphor for a trunk...and then you follow a branch down a twig to the delicious apple at the end but discover skin and flesh and deep inside, the hidden seeds of a whole new tree?