Vinca difformis is a shrub used primarily as a ground cover that bears whitish-blue flowers from May to September. It favours partial to full shade and performs best in sheltered spots. Plant in well-drained sandy or loamy soil with a neutral to slightly acidic pH and keep soil moist but not waterlogged. H4 hardiness indicates average tolerance to UK winter conditions.

Intermediate periwinkle Vinca difformis flowers May to September and suits shaded, well-drained sites as a ground cover or in rock gardens.

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

Vinca is an Old World genus of flowering plants in the family Apocynaceae. The English name periwinkle is shared with the related genus Catharanthus.

Vinca difformis

Intermediate periwinkle | Vinca difformis

Vinca difformis subsp. sardoa is a shrubby ground cover native to Sardinia that suits shady places. It flowers from May to September. Plant in partial to full shade on well-drained sandy or loamy soil and keep soil moist to well-drained. It is rated H4, meaning average hardiness for UK gardens.

Sardinian intermediate periwinkle (Vinca difformis subsp. sardoa) is a shade-tolerant ground cover that flowers from May to September and suits rock.

Vinca difformis subsp. sardoa

Sardinian intermediate periwinkle | Vinca difformis subsp. sardoa

Vinca minor 'Bowles's Variety' is a trailing, evergreen subshrub prized for forming a low, spreading mat by rooting along its stems. Its glossy, leathery leaves remain through winter and its solitary, five-lobed flowers appear from May to September. The plant commonly roots at nodes to create large clonal colonies and can occasionally scramble to about 40 centimetres high. It does not twine or climb.

Vinca minor 'Bowles's Variety' is a trailing evergreen periwinkle with glossy leaves and violet-purple flowers that bloom from May to September.

Vinca minor 'Bowles's Variety'

Common Periwinkle | Vinca minor 'Bowles's Variety'

Vinca minor 'Gertrude Jekyll' is a trailing subshrub in the Apocynaceae that spreads by rooting along its stems to form mats. It bears glossy, dark green leaves and produces solitary violet-purple flowers in the leaf axils. Flowering occurs from May to September.

Vinca minor 'Gertrude Jekyll' is a trailing periwinkle with glossy dark green leaves and violet-purple flowers from May to September.