Image caption Xate palms are popular among florists because the leaves stay green for up to 40 days after being cut

Demand for leaves from an endangered palm, found in Central and South America, is threatening the species' long term survival, a study warns.

Leaves from the xate palm are used by the international flower trade, and are mostly harvested from wild trees.

UK researchers said training locals to cultivate the trees, thus easing the pressure on the wild population, only had a limited success.

The findings have beenpublished in the journal Plos One.

"One of the reasons why florists like this leaf so much is because once you have cut it, it stays green for 30-40 days," explained co-author Sophie Williams, a researcher from Bangor University, Wales.

"There can be about two weeks from the forest to the florist, yet they can still store it for another two or three weeks."

Previous studies had said that the plant, which generally has five leaves, would be damaged if more than two leaves were removed at any one time.

The peak in demand, which is estimated to be worth $4m each year, for the leaves coincides with Mothers' Day and Palm Sunday.

Once harvested, the leaves are transported to Cancun, Mexico, before being exported to destinations including Miami and Amsterdam.

Barriers to growth

Overharvesting is a common threat facing many threatened plant species, and cultivation training is seen as one way to ease the pressure on wild populations.

In detail: Xate palm Xate is pronounced "Shatay"

Scientific name: Chamaedorea ernesti-agusti

Can reach two metres in height

The plants generally grow up to five leaves

It is a shade species; direct sunlight bleaches the leaves

Harvesting more than two leaves from an individual plant damages its reproductive capabilities

In 2006, the UK Darwin Initiative Project and the Belize Botanic Garden set up a training programme, with the aim of giving locals the knowledge to grow and harvest the species rather than harvesting wild palms.

Ms Williams and the team, which included a researcher from the Royal Botanic Gardens, Kew, used the study to assess whether the training programme had a beneficial effect.

"People will often state that we need environmental education or training, and people often see it as a panacea to protect species," she told BBC News.

"I agree that we need these things, but we also need to think about the context in which we are doing them.

"The training programme was great... but we need to look at other factors that could prevent the training from having an impact.

"Just increasing knowledge and awareness doesn't always lead to positive action all the time, and that is often because… there are barriers."

These barriers included long-term land tenure. This could act as a deterrent because it takes four years for the palm (Chamaedorea ernesti-agusti;another common name is fishtail palm) to grow before its leaves can be harvested.

If a farmer could not secure tenure of some land for long enough, then it would not be cost-effective to invest in cultivating the crop.

Access to seeds is another potential problem that could dilute the impact of a training programme.

Ms Williams said if there was not a supply of seeds for farmers, then it could encourage seeds to be taken from the wild population.

This practice, studies suggest, can be more damaging to the palms than harvesting leaves.

Ms Williams, a PhD student, said the next stage of her research is to assess whether increased cultivation is an effective conservation tool and eases the pressure on wild plants, or merely increases the supply of the economically important crop.