I had to smile when I read your post - when I first moved in here 25 years ago I dug up enough 'house-seeds' from the borders to build an extension. I slung them all in a corner. When the time came to shift them I realised I'd nowhere else to put them. I'd always wanted a rockery, so...
I slung a load of soil over them, dotted a few well placed large boulders around (also from the borders - honestly, the garden sank about two feet after they'd been removed!) and planted herbs. It's still there and still going strong. Oh, and the drainage is great.
And for anyone here growing Pineapple Sage from swops, it's where the Grandaddy plant was born!
;D