Definition of "harebell"

How Snow-drops cold, and blue-eyed Harebells blend / Their tender tears, as o'er the stream they bend […] .

1789, Erasmus Darwin, The Loves of the Plants, J. Johnson, page 2

Her most striking feature, then as now, was her eyes: both large and expressive, but while one was the brown of a fresh hazelnut, the other was pale bluey-violet, the colour of harebells.

2020, Jasper Fforde, The Constant Rabbit, page 7

I wonder whether the witches would be wearing on their fingers their ornaments of foxglove blossoms, often called witches' bells or harebells, sometimes known as witches' thimbles.

1940, Rosetta E. Clarkson, Green Enchantments: The Magic Spell of Gardens, The Macmillan Company, page 258