Hello @LordZebedee
Fellow Mancunian here.
I’m sorry to say that planter is not distinctive enough to be considered suitable for a wayspot and as @hankwolfman has said it would also not be a pokestop as the Park is already the 1 allowed pokestop in that cell.
You will need to look slightly further afield. You might be able to get the footbridge in. Have a look at this post What is your favourite bridge/footbridge/tunnel nominations? - #7 by elijustrying of one nearby for ideas.