Vinca difformis

Vinca difformis, the intermediate periwinkle, is a little-known Mediterranean species. It offers small star-shaped flowers of a very pale lilac-blue, with petals more slender than its cousins, the common and large periwinkle. Its bright flowering lasts a long time, from March to May. This vigorous creeping perennial, in moist to damp soil, is perfect for quickly covering difficult areas, including tree roots and under conifers. It forms an elegant carpet composed of evergreen leaves of a bright and shiny green, attractive all year round. Rather sensitive to cold, it should be given a sheltered location in regions with harsh winters, and care should be taken to protect it when the temperature drops below -7°C (19.4°F).

The intermediate periwinkle is a creeping perennial plant with woody stems from the Apocynaceae family, native to the Mediterranean region. In the wild, it is found in shaded or wet areas, populating the base of hedges or in ditches. This plant develops from a woody climbing stem base, producing creeping or erect stems, forming a dense carpet 20 to 30cm (8 to 12in) high and 1 to 2m (3 to 7ft) or more in width. In contact with the ground, the stems produce vigorous roots that allow the plant to continue its lateral growth. The stems bear opposite, ovate, dark green, glabrous and shiny leaves, and produce during spring and sometimes again from September, coiling buds that open into solitary terminal flowers, pale blue becoming almost white over time, tubular at the base, opening into 5 slender, truncate lobes at the top. They measure between 3 and 4cm (1 and 2in) in diameter.

Periwinkles are useful ground covers that can sometimes become invasive in small gardens. They will spread even in shaded areas, although they may be slightly less floriferous. They eventually form thick intermingled mats, effectively covering the ground under trees or shrubs while tolerating their roots. In shade or partial shade, the intermediate periwinkle can be combined with Acanthus mollis, Dichondra repens, Epimedium, lamiums or Cymbalaria muralis, in a slightly wild understory, even under a hedge of thuja or cypress. The 'Gloire de Marengo' ivy, with its fabulous cream-variegated grey-green leaves, will make a beautiful combination with Vinca difformis in regions with mild winters. In the sun, it can accompany, for example, snow-in-summer (Cerastium tomentosum), Waldsteinia ternata, and many other ground covers... The intermediate periwinkle can also be used in shaded hanging baskets and containers, to accompany annual plants.