Hello, Here are 2 flowers from Vietnam, in the coastal area of Da Nang : - one belongs to a sort of high bush covering some slopes, has small yellow flowers with 5 petals and the leaves of the top of the plant are white. - one belongs also to a high bush and has very large purple flowers, around 12/15 cm wide Thank you for your answers
The second one is Mussaenda. Here is a page with some species in Vietnam: Vietnam plants - Cây cỏ Việt Nam: Rubiaceae : Họ Cà phê - Nhóm họ phụ Mussaendeae và Gardenieae The first looks like Tibouchina. Here is a page with a Tibouchina native to Vietnam, but I'm not sure those leaves are a good match.
