Flower of the English bluebell, Hyacinthoides non-scripta ( formerly Endymion non-scriptus). The picture shows two specific features that differentiate the English from the Spanish bluebell ( H. hispanica ) and hybrids between them ( H x massartiana ). The pollen (below centre, to left and right) is a creamy white colour. The petals are blue with a purple tinge, and strongly recurved at the mouth of the flower. Bluebell woods in the UK are thought to contain nearly half of all the world's bluebells. Bluebells are regarded as an indicator of ancient woodland, although, particularly in the North and West of the UK, they may occur in open habitats. The ease with which hybrids with H. hispanica may form is of environmental concern, since both species are grown together in gardens. Bluebells may behave as weeds in gardens; unwanted bulbs should not be discarded into the wider environment.