Once plant that does appear in fairy stories is foxglove. Artists seem to like drawing fairies emerging from the flowers like bumblebees in gowns.

And fungi - toadstools and such with little curly caps.

Another one is the Banksia with its odd seed cones.

All these are more the conventional ideas for artists to show 'little folk' in a fantasy setting. Not like the rampions/Rapunzel connection. (And if my mother had named me after a garlic I'd have been happy to live in a tower, too!)

I have a book called "there are fairies at the bottom of my garden" I bought at Caprilands Herb Farm years ago. It's by Betsey Williams out of Andover Ma. It's a pretty low rent type cover but is charming and has a lot of folklore type of things in it.

Faerie flowers!!
Lots of old stuff about foxglove in folklore; faeries sometimes used them as hats.
English bluebells also have a story -if you heard them ring an evil spirit was nearby.
Clover - the juice of a 4 leaf clover squeezed onto your eyelids would break faierie spells and allow you to see past their illusions.
Pansy was used as a love potion by Oberon, king of the faeries.
Primrose - if you touched the correct number of primroses in a posey to a faerie rock it would open to faerieland. Touch the wrong # and you were doomed.

Ok, got that out of my system.

The flower you are seeking is probably Creeping Bellflower; in Europe they call it Rampion. Campanula rapunculoides is the Latin name. (It is invasive here). Rapunzel is named after the flower, and her exile to the tower is a witch's punishment to the girl's father, who stole rampion from her magic garden to help his wife in childbirth. In another story, a maid who digs up a rampion plant discovers a staircase that leads to a magnificent underground palace -don't ask me, it's a European fable thing. Oh well.

http://www.naturephoto-cz.com/creeping-bellflower:campanula-rapunculoides-photo-831.html

does anyone know what it was about the rampion plant that rapunzel's mother craved? is it edible?