NASA's Valentine's Day Flower Harvest Takes Space Gardening Beyond Romance

— -- Understanding how plants grow in space will be vital to future long-haul missions -- such as one to Mars -- because astronauts will have to grow some of their own food.

American astronaut Scott Kelly, who is toward the end of his scheduled year in space, has been busy tending to a garden on board the International Space Station, growing lettuce and flowers. Meanwhile, a team on the ground is also working on a control experiment that will better inform NASA's vision for having a fully functional garden in space.

"We need to learn a tremendous amount to help develop more robust sustainable food production systems as NASA moves toward long-duration exploration and the journey to Mars," Gioia Massa, a scientist on NASA's "Veggie" team, said in a blog post.

Zinnia flowers were harvested last week from the ground control experiment. Scott Kelly harvested his space zinnias on Valentine's Day. While both are the same flower, scientists will be able to compare them to better understand the different changes plants undergo when growing in space.

Kelly and Dr. Kjell Lindgren were the first astronauts to sample their space garden when they dined on lettuce last year.

“We’re going to have to have a spacecraft that is much more self sustainable with regards to its food supply," Kelly said, explaining the importance the produce experiment will have on a potential future trip to Mars. "There's going to be a long period of time when we’re going to have to be completely self sufficient."

Future astronauts at the International Space Station will also be treated to some more variety. The Veggie team said it plans to send seeds for "Outredgeous" red romaine lettuce and for "Tokyo Bekana" cabbage on a future cargo resupply mission.