The pollen and nectar production of millions of flowers in urban meadows across the UK has been comprehensively measured to help conservationists work out how best to boost pollinators including bees and butterflies.
A team led by Graham Stone at the University of Edinburgh carried out a study of more than two million flowers from annual and perennial species typically grown in wildflower meadows, and associated weeds, by surveying sixty large meadows planted in Edinburgh, Bristol, Leeds and Reading. The project involved working closely with city parks teams and local schools, who planted and looked after each meadow.
The results of this research have now been published in the journal PLOS ONE and demonstrate that wildflower meadows made up of common perennial species (plants that persist for more than two years) provide more food for pollinators than those made up of annual species (that die after one year and grow again from seed).
High performing plants included rough hawkbit, wild carrot, common poppy, black knapweed, corn marigold and dandelions.
Perennial meadows contain more pollen and nectar and also flower earlier in the year, meaning they are best for spring flying insects such as the queens of some bumblebee species and many wild bees, and butterflies coming out of hibernation.
The research shows that a significant contribution to nectar and pollen early in the year comes from weeds such as dandelions and buttercups, which means leaving some of these to flower is likely to be important to early spring pollinators. The research also demonstrates that at some times of the year a single flowering lime tree can produce as much nectar as a single wildflower meadow covering 300 square metres.
Lead author Damien Hicks, from the Institute of Evolutionary Biology at the University of Edinburgh, said: “If you think of a garden or park as a restaurant for pollinators, then the flower species that are planted in it determine both what is on the menu and also when it will be open. Flowers vary enormously in the amount and type of useful food that they produce, and when it is produced.
“The results show that perennial plants can produce up to 20 times as much nectar and six times as much pollen. This could be used to help design habitats that are specifically aimed at boosting the pollinator community, and crucially, this method can be applied to any vegetation type.”
Dr Maggie Keegan, Head of Policy, Scottish Wildlife Trust said: “Creating wildflower meadows in urban areas is an important part of projects such as Edinburgh Living Landscape. We want to create nature-rich spaces that provide as high a biodiversity benefit as possible so this research is vitally important.”
“With thought we can design high quality and connected green spaces in our cities that best combine urban wildflower meadows and trees. The right mix would provide a rich source of food over a long flowering season, packaged in flowers that suit a wide range of different types of pollinators.”
David Jamieson, Head of Parks, Greenspace and Cemeteries, City of Edinburgh Council said: “We welcome these research results as they clearly show how as a local authority we can significantly improve the biodiversity where most people live, work and play simply by changing the way we maintain our urban parks and gardens. It’s a win-win for both wildlife and humans.”
The research, Food for pollinators: quantifying the nectar and pollen resources of urban flower meadows, is published in the open access Journal PLOS ONE.
Edinburgh Living Landscape is a partnership project between the Scottish Wildlife Trust, University of Edinburgh, City of Edinburgh Council, Greensurge, the Royal Botanic Garden Edinburgh and Edinburgh and Lothians Greenspace Trust. It aims to create a city fit for the future with healthy and beautiful areas that are resilient to climate change, highly valued, and accessible to Edinburgh’s citizens. It also aims to make the city one of the most sustainable in Europe by 2050.