These come in a number of flower colors. Plant periwinkle in May in Louisiana to be most successful. Periwinkles planted earlier are prone to root rot problems due to cool soil temperatures. A well-drained raised bed in full sun is need to periwinkles. Recommended pH is 5.4-5.8.
Periwinkles can make it on very limited irrigation.
Mulch with pine straw or a similar material to prevent splashing of soil up onto the foliage - this minimizes disease problems. We mentioned fertilizing spring flowering shrubs in the April edition of the zone report. If you did not get this done in April, May is not too late. Use one to two pounds of actual nitrogen per 1000 square feet of bed area. It is best to use a fertilizer that is classified as a slow-release type.