Zinnias have opened their orange-yellow petals for the first time on the International Space Station.

Grown as part of NASA’s Veggie program, getting these flowers to bloom hasn’t been easy. From excessive water to overdrying to mold, they’ve overcome quite a few hurdles before recovering this month.

To improve zinnia growing conditions in space, NASA named astronaut Scott Kelly an autonomous gardener in December so he could independently decide when the plants needed watering or tending instead of waiting for directives from Earth.

Though the space station crew was successful at growing romaine lettuce in space, zinnias are more challenging to grow since they are more sensitive to light and environmental conditions. Zinnia’s longer growth duration of between 60 to 80 days also make it more challenging.

Many plants have been grown in space — including sunflowers in 2012 — but this program aims to learn how to grow more complicated plants through their entire life cycles and overcome hurdles along the way.

Read more: Zinnias are the First to Bloom in the International Space Station from American Nurseryman Magazine

Editor’s note: This article was originally published in March 2016 and has been updated for accuracy and comprehensiveness.