It is currently impossible to provide a detailed plot synopsis or cast list for a movie titled "Petunia" scheduled for 2026, as no major studio announcements, casting news, or critical reception data exist for a theatrical film with this specific title in the provided knowledge base. The only confirmed media project associated with the name "Petunia" launching on July 16, 2026, is a PC video game titled "Petunia's Purgatory," which is described as a desktop pet simulation involving cursed crops and mutant animals rather than a traditional motion picture.
As there is no confirmed theatrical or streaming release for a movie titled "Petunia" in 2026, viewing options are unavailable for a film by that name. However, if referring to the announced video game "Petunia's Purgatory" (not a movie), it would typically be available on digital distribution platforms upon its July 16, 2026 release.