The effect of life history and weather on onset of flowering and length of flowering period of agricultural weeds

Sammanfattning: With a warming climate and the usage of monocultures in food production it is possible we may face more issues concerning food insecurity in the future as pollinators struggle to find food in agricultural landscapes. Therefore, it is of value to know whether common agricultural weeds are important sources of food for pollinators. Pollinators are vital in the growing of food-crops and may depend on different agricultural weeds during their flying season. This study is based on observational citizen science data on the flowering of 24 agricultural weeds classified as useful to pollinators in the years 2008-2022. Data on first flowering and length of flowering was compared between life history classifications based on life span and time of germination. The results showed that while there is variation both between groups and within groups among the selected species, summer annuals are among the last to start flowering. Species classed as “summer and winter annuals”, i.e that can germinate either in spring or autumn, had a longer flowering period than the other classes. Winter annuals were first to flower while the perennials and “summer and winter annuals” differed more among each other. Weather dependency was also addressed by comparison over years. Overall, the selected species were not significantly affected by mean winter temperature, mean summer temperature or mean summer precipitation.