Plants in office boost employee productivity, a new study shows.

Researchers at the University of Exeter and their colleagues from the Cardiff University have found that green office spaces keep employees happy and productive.

Spartan office spaces - devoid of any pictures, souveniers or other distractions - are considered to be highly productive places. However, the researchers say that these empty places can reduce motivation to work. According to the team, people working in such environment are like ants in an "empty jam jar".

Enriching these lean offices with plants can increase productivity by as much as 15 percent, the researchers have found.

"Our research suggests that investing in landscaping the office with plants will pay off through an increase in office workers' quality of life and productivity," Marlon Nieuwenhuis, from the Cardiff University's School of Psychology.

"Although previous laboratory research pointed in this direction, our research is, to our knowledge, the first to examine this in real offices, showing benefits over the long term. It directly challenges the widely accepted business philosophy that a lean office with clean desks is more productive," said Nieuwenhuis in a news release.

The study was based on data from a call centre in the Netherlands and a large city auditor in London. However, the researchers declined to name the offices that they studied. They said that the work desks were highly organized and devoid of any paintings or other distractions.

The team found a little greenery in the office - a plant per square meter - improved both employee mood and concentration skills, The Guardian reported.

"Psychologically manipulating real workplaces and real jobs adds new depth to our understanding of what is right and what is wrong with existing workspace design and management. We are now developing a template for a genuinely smart office," said Dr Craig Knight, from the University of Exeter, co-author of the study.

Previous research has shown that natural light in office keeps workers healthy and happy