Plants that bloom in May in Zone 11 with blue flowers

Bachelor's Button

True cornflower blue that almost no other flower can match. Cottage garden classic that self-sows reliably.

Larkspur

Tall spires of spurred flowers in deep blue and purple. The annual cousin of delphinium, easier to grow from seed and just as dramatic.

Nigella

Sky-blue flowers wreathed in feathery green bracts give way to ornamental striped seed pods. Self-sows freely once you start.

Plumbago

Sky-blue phlox-like clusters bloom nonstop in warm climates. The blue flower that thrives where most blues melt in summer heat.