Honeybees in towns and cities enjoy a more diverse diet than their rural counterparts, experts said today. The urban bees find a richer diversity of pollen because they visit a much wider range of flowers than bees foraging in the countryside.

At Kensington Palace in London, where the Duke of Gloucester is keeping bees, samples of pollen carried back to the hives this summer contained large amounts of pollen from rock rose, eucalyptus and elderberry. In contrast, pollen samples taken from hives at Nostell Priory in Yorkshire and Barrington Court in Somerset were heavily dominated by just one crop – oilseed rape.

The National Pollen and Aerobiology research unit at the University of Worcester conducted the pollen analysis. Professor John Newbury, the head of the Institute of Science and the Environment, which includes the unit, said the samples provided a snapshot of the flowers honeybees are feeding on, at what time, and where.

"This is important because different flowers can provide different levels of nutrition," he said. "We can also see if bees are feeding entirely on commercial crops which may make them more susceptible if there are any negative effects of agriculture sprays."

The research is part of the National Trust and BBC local radio's Bee Part of It project, which is trying to establish whether there is a link between pollen and the health of bees. Pollen samples were taken between June and August from 10 of the 45 hives involved in the project across England.

At the end of the summer, honey samples will be analysed to provide a broader picture of the plants visited during the summer.

Matthew Oates, nature conservation adviser at the National Trust, said the prelimary findings back what has long been suspected: "namely that bees today often fare better in urban environments than in contemporary farmland".

"Apart from crops such as oilseed rape and field beans, there are precious few pollen sources around for bees and other insects in modern arable farmland and surprisingly little in areas specialising in dairy, beef or sheep production," he said.

Francis Ratnieks of Sussex University, the UK's only bee professor, said his own research – decoding the honeybees' waggle dance which reveals where they forage – shows that bees do not exclusively forage in either urban or just rural areas, but cross between both.

"We know there is more diversity of flowers in cities, with gardens, parks, railway sidings and bits of waste land all planted with different species, but it doesn't necessarily follow that bees are therefore doing better because of it. It is not necessarily greater diversity that is important, they also need an abundance of flowering plants."

A new project at Sussex entitled Helping honeybees in an urban environment, aims to scientifically assess the value of different species of garden plants to honeybees and other pollinators.

Fourteen popular varieties of lavender are being tested along with other popular plants including geraniums, nasturtium, dahlia and borage. Prelimary analysis shows that geraniums are not attractive to bees, and some lavender is more attractive than others. The three-year project, funded by the Body Shop Foundation, will be rolled out next to Kew Gardens and other locations.

"Many people feel enthusiastic about helping honeybees in their current decline, but they often do not know how," said Ratnieks. "One way we can help the public is to find out which plants are bee-friendly that they can grow in their gardens."