Romneya coulterii

Californian Tree Poppy. This is a spectacular shrub-like perennial that gets covered in apricot scented large white poppy flowers in summer (early December through to autumn), tough and drought resistant. Hardy. Sun 1-2m Trim to suit. Spreads a little, easily manageable. In big pots, only 2-3 (just) in a wine box.  

Keep root disturbance to a minimum when planting.