Campanula

A sturdy, upright hardy perennial grown for the dense terminal heads — and tight axillary clusters — of upward- and outward-facing, deep violet-blue (sometimes white or purple) bell-shaped flowers it carries from early to midsummer above clumps of rough, oval basal leaves. POWO (Kew) gives its native range as a broad sweep of the temperate Northern Hemisphere from Britain across Europe and through temperate Asia to Japan and Korea (some 57 botanical countries), where it grows in dry grassland, scrub, and open woodland, often on chalky soils. It is one of the easiest border bellflowers: hardy in USDA zones 3a-8b and rated fully hardy (H7) by the RHS, which gives the rich-blue cultivar "Superba" and the pale "Caroline" its Award of Garden Merit. Plant it in full sun or light shade in ordinary, moisture-retentive soil and it will spread steadily by underground rhizomes to form a colony — vigorous and welcome in a relaxed border, but worth siting where it can run, or lifting and dividing to keep it in bounds. The open clusters are excellent for bees, worked above all by bumblebees. Sources give no edible use, so treat it as an ornamental only.

A classic cottage-garden bellflower grown for its tall, slender stems hung with large, outward-facing, cup- or bell-shaped flowers in clear blue or white through early to mid summer, rising from neat evergreen basal rosettes of narrow, peach-like leaves. POWO (Kew) gives its native range as across Europe and into western Asia and western Siberia, and it has been a staple of cottage borders for centuries. It is happy in full sun or light shade in ordinary, moderately moist soil and is hardy in USDA zones 3a-7b. A long-lived, easy, reliable perennial, it self-seeds readily — a charm when it naturalises through a border and a nuisance when it does not — so deadhead to keep it in bounds and to extend the display. RHS rates the species fully hardy (H7) and gives several forms the Award of Garden Merit. The flowers are a traditional mild edible garnish, and the open bells are excellent for bees, especially long-tongued bumblebees.