The effect of variety and sowing date on the growth, development, yield and quality of common buckwheat (Fagopyrum esculentum Moench)

•Average grain yield of common buckwheat was 0.77 t ha−1 in response to sowing date.•The cool temperate climate resulted in a prolonged (150–190 day) growth cycle.•Late sowing resulted in a 7.5 fold decline in total antioxidant concentration.•Common buckwheat has clear potential in organic and low-input production systems.