The great cultural values of flowers in our life have nourished a highly developed flower industry. However, our current flower trade is still labour-intensive mainly due to a lack of effective automated classification systems. While several image datasets have been established and are widely used for developing visual flower classification models, they are of little practical value to the industry as, in these datasets, few flowers of market value are included, and intra-class and temporal variabilities are also not taken into consideration. Here, we present a large-scale flower image dataset named YNU Flower for flower classification. A total of 91 commercial flower varieties belonging to eleven favoured botanical groups were purchased from the Dounan flower market, the largest flower trading centre in Asia, and 17,806 images were captured. Notably, the YNU Flower dataset includes many commercial varieties with subtle appearance distinctions but significantly different price tags. Using this newly established dataset, we trained several representative models for classification and object detection tasks. By making YNU Flower publicly available to the community, we anticipate that this benchmark dataset will expedite translational research on flower classification and ultimately benefit the flower industry.