Verbena stricta Hoary Vervain Sun: Full Soil: Sand,Loam Moisture: Dry,Medium Height: 2'-4' Bloom:Blue Jul-Sep The robin's egg blue spires are a real standout in the late summer prairie. An important nectar source for butterflies, and the leaves are the larval host food for the Common Buckeye Butterfly. The seeds are important for many small birds and mammals. Very drought resistant, and non-aggressive. Hardy to Zones 3 - 8.