Verbena loves hot dry conditions. Riviera has a naturally compact and bushy habit. The F1 Hybrid vigour gives good disease resistant and an incredible ability to produce flowers. A great product but you must protect them from snails and grow in an area with good air movement.
The plants produce so much flower they can get stressed. A stressed plant is more likely to pick up mildew and other disease problems. By watering around the plants in the morning (keeping foliage dry), you will achieve a magnificent & memorable display!