Exacum is an evergreen, compact and well-branched member of the Gentianaceae grown for its summer flowering. It prefers a south-facing, sheltered site in full sun with neutral, moist loam. Classed H1c (tender), it is not frost-hardy and is best used in pots or locations where it can be protected over winter.

Exacum is a well-branched evergreen that flowers June to September and suits south-facing pots or sheltered borders in neutral, moist loam.

Exacum

Exacum (Gentianaceae) | Summer-flowering for Pots

Gentiana 'Barbara Lyle' is a mat-forming, trailing gentian that forms low clumps and spreads as a ground cover. It produces summer flowers from June to September above semi-evergreen to deciduous foliage. Plant it into loam that is acid to neutral and kept moist but well-drained, in full sun or partial shade. Hardy (H5), it suits south-, east- or west-facing sites and tolerates both exposed and sheltered positions.

Gentiana 'Barbara Lyle' is a mat-forming gentian that flowers June to September and prefers moist, well-drained loam in full sun or partial shade.

Gentiana 'Barbara Lyle'

Gentiana 'Barbara Lyle' | Trailing mat-forming gentian

Gentiana asclepiadea is a perennial herbaceous member of the Gentianaceae, grown for its summer flowering. Native from Europe to Iran, it suits moist, humus-rich, well-drained soils and tolerates both partial shade and full sun. It is hardy to H5 and prefers sheltered to semi-exposed locations and northerly, easterly or westerly aspects. Flowering runs from June to September, offering an extended summer display.

Willow gentian (Gentiana asclepiadea) prefers moist, humus-rich, well-drained soil in partial shade and flowers from June to September.

https://en.wikipedia.org/wiki/Gentiana_asclepiadea

Gentiana is a genus of flowering plants belonging to the gentian family (Gentianaceae), the tribe Gentianeae, and the monophyletic subtribe Gentianinae. With over 300 species, it is considered a large genus.

Gentiana asclepiadea

Willow gentian | Gentiana asclepiadea

Gentiana asclepiadea 'Knightshayes' is a shade-tolerant perennial gentian that flowers from June to September. It originates from Central and Eastern Europe where it favours woodland conditions. In cultivation it performs best in moist, humus-rich, well-drained soil with an acidic to neutral pH. Position it in a sheltered, north- or east-facing spot out of strong sun.

Gentian (Gentiana asclepiadea 'Knightshayes') is a shade-loving perennial that flowers June–September and prefers moist, humus-rich, acidic to neutral.

Gentiana asclepiadea 'Knightshayes'

Gentiana asclepiadea 'Nana' is a mat-forming gentian in the family Gentianaceae that forms low, trailing clumps. It bears trumpet-shaped, deep blue flowers from June to September. The foliage is semi-evergreen and the plant remains in compact tufts. It prefers moist but well-drained loam in full sun or partial shade.

Gentiana asclepiadea 'Nana' forms low, mat-forming clumps with deep blue, trumpet-shaped flowers from June to September.

Gentiana asclepiadea 'Nana'

Willow Gentian (Gentiana asclepiadea 'Nana') | Blue blooms

Gentiana asclepiadea 'Phaeina' or 'Celestina' or 'Phyllis' is a summer-flowering perennial in the Gentianaceae, noted for deep blue blooms from June to September. It comes from central and eastern Europe and suits shady, moisture-retentive sites. Plant it in partial shade or shade on humus-rich, well-drained soil with a neutral to slightly acidic pH. Rated H5 (hardy), it works well in woodland gardens, rock gardens and borders.

Gentiana asclepiadea 'Phaeina' or 'Celestina' or 'Phyllis' is a hardy shade perennial for moist, humus-rich, neutral to slightly acidic soils that flowers.

Gentiana asclepiadea 'Phaeina' or 'Celestina' or 'Phyllis'

Willow Gentian | Gentiana asclepiadea 'Phaeina' or 'Celestina' or 'Phyllis'

Gentiana asclepiadea alba of gardens is a perennial herbaceous gentian that flowers from June to September. It belongs to the Gentianaceae and originates from central and eastern Europe. Plant in partial shade or full shade on moist, humus-rich soil with an acidic to neutral pH. Give it a north- or east-facing, sheltered position for best results.

Willow gentian 'Alba' (Gentiana asclepiadea alba of gardens) flowers from June to September in sheltered, north- or east-facing shade on moist, humus-rich.

Gentiana asclepiadea alba of gardens

Willow gentian 'Alba' | Gentiana asclepiadea alba of gardens

Gentiana lutea is a perennial herb reaching about 1.2 m, most notable for its yellow summer flowers. It belongs to the gentian family (Gentianaceae) and is native to Europe. Flowering runs from June to September. Plants form erect stems suited to exposed, sunny positions.

Great yellow gentian (Gentiana lutea) is a tall European perennial that flowers June to September and prefers full sun on neutral to alkaline, moist soils.

https://en.wikipedia.org/wiki/Gentiana_lutea

Gentiana lutea

Great yellow gentian | Gentiana lutea

Gentiana makinoi 'Marsha'PBR is a mat-forming gentian that produces trailing, tufted clumps. Its foliage can be semi-evergreen to deciduous and it suits full sun or partial shade. It prefers loam that is moist but well-drained and is rated H5 (hardy). Flowering occurs from June to September.

Gentiana makinoi 'Marsha'PBR is a mat-forming gentian flowering June to September, for loam soils in sun or partial shade.

Gentiana makinoi 'Marsha'PBR

Gentiana makinoi 'Marsha'PBR | Mat-forming Gentian

Gentiana triflora is a perennial gentian reaching about 0.5 m that flowers from June to September. It is native to China, Mongolia, eastern Russia, Korea and Japan. Plants prefer full sun and a moist but well-drained soil, accepting sandy, loamy or clay types. In the UK it is fully hardy (H7).

Clustered Gentian (Gentiana triflora) flowers from June to September and prefers full sun with moist, well-drained sandy to clay soils.

https://en.wikipedia.org/wiki/Gentiana_triflora

Gentiana triflora

Clustered Gentian | Gentiana triflora

Swertia petiolata is a member of the gentian family (Gentianaceae) that favours moist to wet ground. It reaches about 0.6 m in height and tolerates sandy, loamy or clay soils. Flowering occurs from July to September. The species is rated H6 for UK hardiness and corresponds to USDA zones 6–9.

Swertia petiolata prefers moist to wet sandy, loamy or clay soils and flowers from July to September.

Swertia is a genus in the gentian family containing plants sometimes referred to as the felworts. Some species bear very showy purple and blue flowers.