An unexpected treat is flowering in the corner of one of our garden beds. Perennial ageratum (Conoclinum coelestinum), a native relative of the annual bedding plant, volunteered behind the old metal wheelbarrow, and is flourishing even in the drought. The clear blue flowers are lovely against the evergreen backdrop of Viburnums and Winter honeysuckle.
A common plant in ditches and field edges, it's really a wonderfully garden-worthy plant, providing a late season spot of color, and to me, remarkable hardiness without any water.