Origin and appearance
Periwinkle (Vinca) is a type of the family of the dog-poison-seed-seed (Apocynaceae), that is spread from Europe to West-Asia and to which approximately a scarcely dozen types are counted. In our native deciduous forests there are two of them: the Great Periwinkle and the Small Periwinkle (Vinca major and Vinca minor). As its name suggests, the evergreen keeps its dark green, shiny, egg-shaped to lanceolate leaves throughout the year. Both the large and the small evergreen form long runners and quickly conquer larger areas. Since its shoots are woody, periwinkle is actually one of the woody plants. However, both species are used like perennials because of their small size – the small Periwinkle grows to 10 to 15 cm high, the large to 20 to 30 cm high. Periwinkle is poisonous as a poisonous dog plant in all parts of the plant.
From April to May, the flowers of both species open, while those of the evergreen with a diameter of up to centimeters are slightly larger. The flowers are mostly single, rarely in pairs, in the leaf axils. Its five blue, violet or white petals are tube-like. After fertilisation, bellows fruits up to 4 centimeters long with four to eight seeds each are formed.
In nurseries breeding forms of both species are available. The Periwinkle variety ‘Variegata’ is decorated with white and yellow leaves. Alba’ blooms white, ‘Reticulata’ light blue and shows yellow veined foliage. The small periwinkle ‘Alba’ has very large, white, ‘Rubra’ red-violet flowers. Filled ‘Azurea Plena’ bloom in blue or ‘Multiplex’ bloom in purple red.
They feels most at home on loose, nutrient-rich soil in the light shade of deciduous trees and shrubs. The large periwinkle likes to stand at somewhat warmer and drier tree edges, the small periwinkle also thrives in cooler, more humid places.
The large and the small Periwinkle are very pretty and robust groundcovers for shady places and for underplanting, also in public green areas. They look most beautiful in combination with high shade shrubs such as Astilbe, Digitalis or Geranium. The blue-flowering groundcover with its dark green shiny foliage forms a beautiful backdrop for yellow daffodils in spring, and the small periwinkle is also suitable for underplanting competitively weak shrubs such as witch hazel (Hamamelis) or flower dogwood (Cornus kousa), as it does not cause strong root pressure. The large evergreen is to be enjoyed in the garden with a little caution – especially the wild species tends to grow in favourable locations and can completely overgrow smaller perennials and shrubs.
The large and small Periwinkle are best planted in spring, as the evergreen leaves of the plants that have not yet taken root are susceptible to frost damage. Before you start, you should clear the soil of all root weeds. Nutrient-poor soils are improved with compost. A pruning of the shoots during planting promotes branching and thus provides better soil coverage.
Periwinkle does not have to be cut regularly. However, if it spreads too much, it can be shortened considerably – best in spring, just above the ground. Sufficient branching and dormant buds should remain.
In rough locations and at locations exposed to the wind and sun, the large evergreen was to be given a winter shelter made of leaves.
further care tips
Both the large and the small periwinkle develop better if a thin layer of mature compost is spread between the plants every spring.
Evergreen can be propagated very easily by cuttings – in addition one simply removes the rooted side shoots in spring. Both species can also be shared in spring. The propagation by cuttings is also very simple – it is sufficient to remove the foliage from the shoots and place them in a shady place in moist, humus-rich soil.
Diseases and pests
Especially mushrooms can cause periwinkle problems. Rust fungi, leaf spot diseases or root neck and stem rot occur in high humidity and wet soils. As a preventive measure, periwinkle is placed in such a way that the air can circulate well.