Experiments on plant cultivation continue on the International Space Station. In August 2015, NASA astronauts tasted fresh lettuce grown in orbit for the first time; now the goal is to improve the performance of their small orchards. Specifically, they aim to obtain several harvests of each lettuce, which would entail more opportunities to consume fresh food for the crew and also more scientific material.
As explained by NASA on its website, astronaut Shane Kimbrough is officially a part-time gardener in orbit, with ground-based support from Kennedy Space Center professionals.

Since 25 October, Kimbrough has been involved in a new stage of the so-called Veggie experiment, in which he is testing a crop technique called "cut-and-come-again". It is based on the selection of only a few leaves of lettuce for consumption, or to use as scientific samples. The rest of the leaves and the nucleus of the plant are left intact so that they continue growing and producing more leaves, which will be harvested after about ten days. It is the first time that all cultivated lettuces have been grown simultaneously in space, stresses NASA.

At first, an excess of water made their growth difficult, but now the first leaves have been harvested and they have been used entirely for the enjoyment of the astronauts, who consumed them in early December. In total, four harvests of this generation of lettuces are expected. The last will arrive around the New Year.

With a view to long-term missions
These types of experiments are primarily carried out with future long-lasting missions in mind, including landing on Mars. "These will require crew members to grow their own food, so understanding how plants respond to microgravity is an important step forward," explains the US agency on the Veggie experiment portal, which not only studies the technologies and the productivity, but also the effects that the cultivation of plants has on the mood of the crew.

Source: lavanguardia.com