What does it mean in other words?
as though from the momentum of its run.

THE CONTEXT:

The lawn started at the beach and ran toward the front door for a quarter of a mile, jumping over sundials and brick walks and burning gardens—finally when it reached the house drifting up the side in bright vines as though from the momentum of its run.

Question

What does it mean in other words?
as though from the momentum of its run.

THE CONTEXT:

The lawn started at the beach and ran toward the front door for a quarter of a mile, jumping over sundials and brick walks and burning gardens—finally when it reached the house drifting up the side in bright vines as though from the momentum of its run.

Answer

As you run, you gather momentum.  If someone suddenly runs in front of you, you may crash into them.

The author talks about the lawn "running".  They suggest that the vines growing on the side of the house are part of the lawn, running up the walls of the house because they had gathered so much momentum.

Answer

It's quite expressive.  This is a massive lawn.  The final piece of the lawn is elevated.  The author describes the lawn as a thing which runs.  If you imagine trying to stop a running dog, you will probably lift it off the ground to slow it down.   The writer is making a comparison between the lawn and the shape of the trajectory of the dog in my example.