These flowers were found in the Brookbanks Ravine in Don Mills, beside the creek.
I believe this is a photo of Ficaria verna, a highly invasive, non-native plant, commonly known as lesser celandine or pilewort. This plant should not be included in a home garden. At this time naturalists and master gardeners are attempting to remove this plant from our ravines. This is a tedious and likely thankless task as the plant has a mist of roots together with small tubers that can be easily disturbed and spread about. Since Ficaria verna emerges well before most native species, it has a developmental advantage which allows it to establish and dominate natural areas rapidly, replacing such native ephemeral plants as trillium, bellworts, wild ginger, blood root and other spring flowering natives. Once established, and native plants are displaced, the ground is left barren and susceptible to erosion, from June to February, during the plant’s six-month dormancy phase. More about this plant here More about lesser Celandine