Hoary vervain, Verbena stricta
 
A pollinator magnet attracts bees, butterflies and hummingbirds with its nectar. The flower spikes add a touch of blue to a sunny, dry garden and bloom throughout July and August. Hoary vervain's flowers are bigger, and the tips of the stalks are rounder than those of blue vervain.
 
Ecology:
Hoary vervain is a host plant to moth species and supports pollen specialist bees.
The seeds are loved by birds, and the stems are homes for stem-nesting bees. 
 
Growing conditions:
Hoary vervain is a short-lived plant that thrives in sunny, dry, disturbed sites like old fields and grazed pastures, where it can reproduce from seed and has low competition. This means for the garden that the soil cannot be entirely mulched for vervain stands to renew themselves, and that hoary vervain should not be planted with aggressive plants. Hoary vervain is very drought-tolerant and can grow in average to sandy, dry soil.