(Editor's Note: This article was originally published on December 13, 2008. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
Few groundcovers lend themselves to both sun or shade but there is at least one plant that can cross borders; the common periwinkle or myrtle, Vinca minor. Most gardeners are familiar with periwinkle; some even curse it as plants can be quite aggressive. However, judicious pruning can help keep the rambunctious spreader under control. Meanwhile, other gardeners have a tough time getting this plant established. Part shade with organic-rich, moist yet well-drained soil, is the ideal combination for maximum growth of this European native. However, they will tolerate full sun if the soil is reasonably moist or alternatively full shade, even though flowering will be reduced in the latter situation. Their leaves are apt to burn in winter if grown in full sun but new spring growth will quickly replace any damaged leaves. The solitary, 5-petalled blossoms are produced in early spring and even sporadically all summer and into fall. They are hardy to zone 4. It should be noted that all parts of this plant are highly toxic.
Of the six species of Vinca that exist, this species shows the most variation in regards to flowers and foliage. The wild species has blue-violet flowers. The most popular cultivar with similarly-coloured flowers is ‘Bowle's Variety' (aka ‘La Grave') with large 2.5 cm flowers. ‘Atropurpurea' has reddish-violet blooms while ‘Gertrude Jekyll' and ‘Alba' have creamy-white flowers. Double-flowered selections also exist although they are hard to come by. ‘Plena' has double blue-violet flowers, ‘Temptation' double lavender, ‘Multiplex' double purple and ‘Alboplena' double white.
The most common single-flowered cultivars are 'Bowle's Variety', 'Alba' and 'Atropurpurea'
As with so many other plants that have been in cultivation for many years, variegated sports have arisen. Gardeners and plant breeders are quick to spot and take advantage of these mutations. Some of the variegated selections include ‘Argenteovariegata' and ‘Sterling Silver' both with white-edged leaves and blue flowers; ‘Ralph Shugert' has white-edged leaves and purple flowers; ‘Aureovariegata' has yellow-edged leaves and blue flowers; ‘Blue and Gold' also has yellow-edged leaves but darker blue flowers than ‘Aureovariegata'; ‘Bowle's Golden' and ‘Albovariegata' both have yellow-edged leaves and white flowers.
Among the variegated periwinkle are 'Albovariegata (flower and foliage), 'Argenteovariegata' and 'Sterling Silver'
Perhaps the most lovely variegated periwinkle is the relatively new selection called ‘Illumination'. This one has reverse-variegated foliage whose leaves are yellow with a green margin. This one is very popular for use in containers and hanging baskets. Often sold as an annual, it is indeed perennial although not as tough as the standard periwinkle. Also new on the market is ‘Sunny Skies' whose foliage is irregularly edged and streaked with bright yellow. Both of these cultivars have standard blue-violet flowers.
Shown above are floral and foliage details of 'Illumination'
As you can see, there have been some wonderful selections made from periwinkle over the years. The variegated ones make lovely additions to hanging baskets and window boxes or can help brighten up a shady area of the garden. The spring floral display is not without merit. Tulips and daffodils may be naturalized among a bed of periwinkle for a stunning spring display. These are just a few of the uses of this tough little groundcover.
I would like to thank the following people for the use of their pictures: Evert ('Atropurpurea') and hensler ('Alba' and 'Illumination' (flower and foliage)