Where I live in South Wales its noticeable how much shorter the growing season is compared to places at lower altitudes; bluebells for example have only just really got going in the last week. Traditionally one of the Lily Family Liliaceae, that are characterised by having flower parts in 3s and parallel veined leaves, this large family has now been divided into different families. Bluebell Hyacinthoides non-scripta is now a member of the Asparagus Family Asparagaceae.
A useful table of features between the different bluebells is found here.
Poland and Clement draw attention to there being viscid spiral fibres present when the leaf is torn. The leaf edges are hyaline (translucent) and blunt toothed or crenelate. The underside of the leaf has fine parallel ribs running along the centre.