Hyacinthoides hispanica

The Spanish Bluebell, commonly grown in our gardens, is more vigorous than our native species and can crossbreed with the native to create a fertile hybrid. This is a problem, as crossbreeding dilutes the unique characteristics of our native Bluebell.
Noticeable differences between the two are as follows:
Native bluebells...

have narrow leaves, usually about 1cm or 1.5cm wide,
have deep blue (sometimes white, rarely pink), narrow, tube-like flowers, with the very tips curled right back.
have flowers mostly on one side of the stem only, and distinctly drooping, or nodding, at the top
have a distinct, sweetish scent
Inside the flowers, the anthers with the pollen are usually cream.

Spanish bluebells...

have broad leaves often 3cm wide
have paler blue (quite often pink and white ones too), conical or bell-shaped flowers that have spread-out tips.
have flowers all round the upright stem
have almost no scent.
Inside the flowers, the anthers with the pollen usually blue (although this may vary a little).

Hybrids between these two are very common, with a whole range of intermediate characters. The hybrids are often abundant in gardens and in woods near to urban areas