Verbena are long blooming perennial flowers that possess the virtues of heat tolerance and an extremely long bloom season. Many perennial verbenas are relatively short lived, but their vigor and heavy flowering make up for this defect. They do well grown as annual flowering plants also, since they bloom quickly during the first season after planting. Verbena are mainly grown for their remarkable length of bloom with most blooming from spring until close to frost if trimmed back once or twice in mid summer. Flower color ranges from white through pink, red, lavender, blue and purple. Verbenas require a location that receives full sun throughout the day. They must have well-drained soil.
While established verbenas are drought tolerant, performance, bloom, and growth rate will be reduced if they are too dry for a long period. During their blooming period, give them a thorough watering once a week if they do not receive an inch of rain that week. Avoid overhead watering.
If bloom slows during the summer, trim the whole plant back by about one fourth of its height and spread, water thoroughly and fertilize lightly. The plant will return to bloom within 2 to 3 weeks.
A light application of a complete fertilizer such as 16-4-8 in mid to late spring and again after trimming back will revitalize plants, but additional fertilization is not generally required. Plants growing in very sandy, poor soil may need more frequent fertilization.