Arabidopsis is the first plant to flower and produce seeds under the zero-gravity conditions of space in 1982 as opposed to the orange zinnia in 2016.
In 1982, the Arabidopsis plants were grown under continuous lighting for 69 days in Soviet Union’s Salyut-7. They developed pink flowers and developed pods. The pods ripened and developed seeds. Around 200 seeds were produced in space and brought back to Earth. This plant holds Guinness records for the first species of plant to flower in space.
In 2012, Astronaut Don Pettit grew a sunflower on the ISS in a spacecraft orbiting Earth and was part of a long space mission. Along with it he had grown Broccoli in space.
By these reports, it can be concluded that the Zinnia is not the first flower to blossom in space. Flower of the Arabidopsis plant is the first flower to blossom in the space.