Also known as Myrtle. Periwinkle is probably the most popular evergreen groundcover. This colourful selection forms a dense mat of glossy dark green leaves edged in white, studded with bright blue flowers in spring. Tolerates dry shade once plants are established. Stems root into the ground readily, and the new plants that form may be easily moved to a new location in spring or early fall. Mowing the patch low after blooming every couple of years will help to keep it thick and weed resistant. Plant 4 to 10 plants per square yard. May be considered invasive in some areas, do not discard unwanted plants in compost or in natural areas where these can become established.