Flower Power by Mark di Suvero.
The artist created this steel sculpture for the International Sculpture Symposium in Toronto in 1967, and it originally resided in High Park. But in 2008, the city returned Flower Power to di Suvero for restoration, and it now lives on the charmingly-named Iceboat Terrace, just off Spadina Avenue.
Turns out that I’d encountered the work Mark di Suvero before when I took some photos of his Joie de Vivre sculpture in Manhatten. The red girders did seem very familiar!