Reviewing published and grey literature in local European languages to supplement existing databases on floral resource traits

Abstract The aim of the study was to collect data on plant phenology, density of flowers and production of floral resources in European countries, using published and grey literature written in local languages. The search was conducted in 11 European languages (Danish, Dutch, French, German, Greek, Italian, Norwegian Bokmål, Portuguese, Romanian, Spanish and Swedish) and included published and unpublished data from local journals, books, databases or master and doctoral theses. The collection contains 2382 records for 1132 plant species from 113 families. Most of the data collected is on flowering phenology, with a relatively large amount of data on nectar/sugar production and less on pollen production and floral density (1474, 1141, 325 and 152 records, respectively). Our study is unique in collecting data on floral resource traits in local European languages. The data collected are a valuable addition to existing floral resource trait databases and can help to quantify the floral resources available to pollinators and other organisms that depend on them for food in different habitats and ecosystems. At the same time, our collection, in combination with other databases on floral resource traits, allows the identification of plant genera and families for which information is scarce, as well as the best‐studied plants and countries where research on floral resource traits has a long tradition. Synthesis and applications. Our research shows the value of using data published in local languages, often as grey literature, especially when building ecological databases of various kinds. Much of the basic data we collected on floral resource traits is available in literature published long ago, making it even more difficult for the research community to access. We discussed several technical issues that can be encountered when collecting such floristic data, especially if the data are to be further used in modelling.