Dubbed Harmony Floralscape, the ambient marketing stunt is aimed at highlighting the environmental credentials of the Toyota's hybrid Prius.
The 30 x 60 foot display depicts the silhouette of a stylised Prius against the backdrop of a rising sun.
The scheme has been launched by Los Angeles mayor Antonio Villaraigosa and Toyota executives.
The floral display, which is appearing by the side of the Pasadena Freeway, is one of seven murals installed in the Los Angeles area. Toyota is installing two more displays in San Francisco.
The campaign is the brainchild of Greenroad Media and uses the firm's Living Pixel technology, which enables designs to be realised in flower-form.
Villaraigosa said: "We are proud to be the inaugural city to unveil the first of seven Floralscapes along one of our busiest highways.
"The commute for Angelenos will now be brightened by floral murals that embody the city's progressive approach to solving environmental issues by merging beautification, sustainable design and reducing our carbon footprint."
The floral campaign has been designed to complement Toyota's overarching Harmony Between Man, Nature and Machine advertising, created by Saatchi & Saatchi LA.