The Matthiola Arborescens is a member of the Brassicaceae family. It's related to cabbages and cauliflowers but its closer relatives include the Night scented stock. Also known as the Tree Stock, it is a hardy perennial that produces a beautifully scented white flowers in spring (this is var. alba, the species plant has purple flowers). 
It's dead simple to grow and and provides a heavenly scent at night time. I don't understand why its not more popular
Matthiola with Phygelius (cape fuchsia) to the right, cerinthe to the left and hypericum behind
