Key:
1a. Leaf blades coriaceous (leathery), lustrous, evergreen, all or mostly less than 8 mm wide; stems prostrate or trailing; corollas with 4 lobes, fruit a red or dark red berry.
2a. Leaf blades pale green below with scattered minute black glands; corollas bell-shaped, cleft to about half their length, lobes ascending or slightly spreading; pedicels less than 5 mm (shorter than the flowers or fruit)
V. vitis-idaea
1b. Leaf blades herbaceous, not lustrous, of various widths; stems prostrate or erect, not trailing; corollas with 5 lobes, fruit a blue or blue-black berry.
Etymology: Vaccinium: ancient Latin name for bilberry, origin obscure