Pbi Home & Garden, the Bayer subsidiary that owns the brand, is spending £1.2 million to support a national campaign to break the domination of the market by Scotts Company's Evergreen.
The five spots by Mitchell Patterson Grime Mitchell - the first by the agency since it won the creative task last August - feature a woman playing with her dog, a man dozing in a hammock and cast-off clothing blowing suggestively across a lush lawn.
The advertising, due to run throughout the spring and early summer, comes on the back of a revamping of the Phostrogen range.
The new advertising, under the theme "Phostrogently does it", promotes the Phostrogen Feed, Weed and Mosskiller, which can be dispensed directly on to the grass without mixing or measuring.
Neil Patterson, a Mitchell Patterson creative partner, added: "Phostrogen's problem has always been that it sounds very scientific. Our job has been to bring the brand to life."
The commercials were written by James Muggridge, art directed by John Taylor and directed by Terence Stevens-Prior through Mustard.