Tết is the biggest festival in Vietnam, it is the lunar New year. This year is the year of the Tiger (Canh Dần). If you visit Vietnam this time of the year, you'll see flowers displaying everywhere. You can see flowers in public park, in the streets, in office building, commercial buildings and private houses...
The traditional Tết flower in the South Vietnam is "Mai" flower (this name has the same sound as "lucky" in Vietnamese). In the North Vienam, the temperature is colder and the traditional Tết flower is peach (hoa đào). Recently, orchids  become favorite flowers to many Vietnameses, because they are beautiful and more expensive. Most orchids are grown commercially in Dalat (central highland) and in the North.

You can see some Tết flowers in my webpage Vietnamese flowers.