Damn!

I was so upset to see I couldn't sit on the plants.
It was the only reason I'd left home and hearth.

Have I mentioned how cold it is?
We're well into summer, but you'd never know.
I finally gave in and lit a fire.

I just noticed Billy in the corner.
He was clearly planning something.

I might suggest to the shop owners who conceived of and planted the sign, that they change it.
I think, 'PLEASE DON'T SIT ON THE PETUNIAS' is much better.