“Ms. de Groot came late to painting, in her mid-40s. But for the next four decades she was prolific, using a palette knife to etch dozens and dozens of scintillating, layered, small-scale seascapes of Provincetown Harbor as seen from the home and studio she designed for herself and her husband … With room to spare under an M-shaped double-gable roof, Ms. de Groot often played summer landlord to creative figures like [John]Waters” – who called her “bohemian royalty” – “[Peter] Hoare, the painter Richard Baker and the gallerists Pat Hearn and Colin de Land.”