Wildlife Gardening Forum trustee and RSPB wildlife gardening expert Adrian Thomas, who has written an inaugural Best Garden Plants for Wildlife report, says: "One of the most common questions in wildlife gardening is: ‘What should I plant in my garden to benefit wildlife?’ There is a plethora of lists available to gardeners in the UK offering suggestions, published in a wide range of wildlife gardening books and on websites.
"However, Garbuzov and Ratnieks (2014) concluded that of 15 lists they analysed, specifically of plants recommended for pollinators, they often included poor recommendations, omitted many good plants, lacked detail and were almost invariably based on their authors’ general expertise rather than on empirical data."
By combining and averaging more than 6,500 scores from 29 experienced participants, the forum was able to create lists of top plants — a kind of "best plant charts" — showing which plants are consistently excellent.
Thomas adds: "Interestingly, there are some plants that are often recommended as being good for pollinators, such as primrose and pot marigold, that did not score highly in the survey. Conversely, some more unusual plants not normally recommended for wildlife were identified as being excellent and might enter the charts in future if more observations are made to confirm this."
He points out that the "ideal solution" to find out which plants are best for wildlife is a scientific study using trial plots with control conditions in several different locations around the UK, inwhich thousands of different plants and their cultivars are compared with each other.
Professor Francis Ratnieks from the University of Sussex’s Laboratory of Apiculture & Social Insects, which has published a new study showing "most flowering varieties being sold to the public in England are relatively unattractive to flower-visiting insects".
Ratnieks’ researchers surveyed 59-74 plant varieties in bloom across six garden centres in Sussex. "Our study aimed to determine how bee-friendly the plants on sale in garden centres are," he explains. "Most are not very much visited by bees and other insects. Therefore, there is great scope for improvement.
"In addition, garden centres are places where plants can be checked for how bee-friendly they are (the people who work in a garden centre could do this). More generally, there is scope for improving the supply chain in terms of bee-friendliness, and garden centres are part of this."
He adds: "If most private gardeners obtain most of their garden plants from garden centres, then on the whole urban gardens are probably not as friendly to flower-visiting insects as they could potentially be."
He says pollinator-friendly labels are often just "marketing" rather than scientific recommendations.