WHEN FINANCIAL services firm PricewaterhouseCoopers refurbishes its offices, foliage is a priority.

"We tend to look quite closely at plants," says Anne Muirhead, head of the firm's future working environment in Britain. They soften the space and improve employees' moods, as well as removing toxins and CO2 from the air, she adds.

"It gives a feeling of having some of the outside in the office. We do a quarterly survey and having plants around the place definitely makes people feel happier."

The apparent triviality of the issue of office greenery can overwhelm any discussion of its benefits. However, there is evidence to suggest that plants improve the workplace.

Research at Washington State University in the US has shown that those in an office with plants experienced a 12 per cent improvement in reaction times when compared with those in a plant-free office, as well as lower blood pressure and quicker recovery from stress.

A study by the Agricultural University of Norway of oil company Statoil's offices found that in work areas that introduced plants, the number of people complaining of fatigue and headaches fell by 30 per cent and 20 per cent respectively. It even showed that people reported a 25 per cent improvement in dry skin problems.

Auditor KPMG is convinced of the importance of office foliage.

Guy Stallard, director of facilities for KPMG Europe, says: "We have plants throughout buildings and in meeting rooms. They improve the ambiance of the space and provide a natural way of breaking up open-plan offices.

"Dust is reduced, the air is fresher and, by moving them around, you have an easy way of changing the working environment."

Derek Clements-Croome, professor of construction engineering at Reading university, says: "Plants and greenery provide a better working environment from the point of view of calmness, but they also absorb VOCs [volatile organic compounds, often emitted by photocopiers], CO2 and tend to make the air a little moister and cooler.

"Plants don't solve everything but they do make people feel happier," he adds. "You can't just buy the odd pot plant, though. It has to be designed in - we're talking about interior landscaping."

There are also some potential downsides to consider. You need to have someone to water them, which is why most offices buy plants on contract.

Plants also need to be fit for purpose - humidity-loving plants struggle in climate-controlled offices. Widely varying light levels can mean uniform planting is impractical and you should choose non-flowering species, as flowering plants can trigger hayfever.

Like many aspects of interior design, employees tend to be happier if they are able to feed their own thoughts into plans.

"We're not prescriptive and we give office managers quite a bit of leeway," Anne Muirhead says. "People feel they've had some input. In fact, there are people who like them so much, they 'adopt' their local plant."

This sometimes brings its own difficulties, though. "We do have problems with them being overfed and overwatered," she says.

- (Financial Times service)