Short answer
The hydrangea (hortênsia) is the flower that famously lines many Azorean roads in summer, especially from June to August. These blue, pink or white blooms thrive in the islands' humid, mild climate and are a signature sight on São Miguel, Terceira, Faial and others. Exact peak timing varies by island and altitude, so ask locally or check seasonal guides.
General information, not legal or tax advice. Rules and amounts change: confirm with official sources.