This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Where the soil is sandy there are frequently wide tracts of uniform so-called heath which are made up of a characteristic type of vegetation. They are more or less ancient pastures that have not, owing to the sandy, rather sterile nature of the soil, been cultivated or turned into arable land. Consequently they are distinguishable from ordinary pasture or meadow.
Though typical heath plants are found upon the grass heath, they may be entirely absent. As the name denotes, this type of association is largely characterized by the predominance of Grasses. The following plants are also typical of the grass heath: Climbing Fumitory, Whitlow Grass, Teesdale's Cress, Dog Violet, Milkwort, Field duckweed, Sand Spurrey, Pearlwort, Grassy Stitchwort, Pretty St. John's Wort, Perforate St. John's Wort, Purging Flax, Jagged-leaved Crane's Bill, Stork's Bill, Furze, Broom, Creeping Rest-harrow, Subterranean Trefoil, Hare's Foot Trefoil, Bird's Foot, Narrow - leaved Vetch, Silvery - leaved Tormentil, Parsley Piert, Burnet Saxifrage, Ladies' Bedstraw, Heath Bedstraw, Least Cudweed, Heath Ragwort, Hawkweeds, Autumnal Hawkbit, Carline Thistle, Sheep's Bit Scabious, Harebell, Ling, Bell Heather, Centaury, Dwarf Forget-me-not, Eyebright, Wood Sage, Wild Thyme, Knawel, Sheep's Sorrel, Field Spike Rush, Vernal Grass, Bent Grass, Sheep's Fescue, etc.