JUST SAY NO, SON! Parker gets maternal with Hunter Parrish.

Photo: Cliff Lipson/Showtime

Few shows change as much as Weeds has without completely alienating their early admirers. Yes, the series, which begins its third season Monday 13, still chronicles the misadventures of pot-peddling suburban widow Nancy Botwin (Mary Louise Parker), who’s still vexed by her spastic brother-in-law (Justin Kirk); her friendly nemesis Celia Hodes (Elizabeth Perkins); and Doug Wilson (Kevin Nealon), the accountant and local politician who’s Nancy’s best customer. But over the course of last year’s 12 episodes, the humor became broader and the underlying sense of longing and frustration (which frequently recalled Six Feet Under) became one of several emotional colors instead of the dominant one. The multiple cliff-hangers that ended season two ran counter to the series’s original, more realistic tone, but they were set up so cleverly that it was hard for loyal viewers to feel betrayed.

In the new season, Weeds continues its metamorphosis into a melodramatic sitcom, and while the characters’ circumstances are less plausible than ever, creator Jenji Kohan has maintained a sense of consistency by enriching elements that have been around since the beginning—most notably, the racial dynamic. The sexual tension between Nancy and her African-American growmeister Conrad (Romany Malco) has now given way to a battle for alpha-dog status between Conrad and U-Turn (the fearsome Page Kennedy), a dealer to whom Conrad and Nancy owe big bucks and who taunts Conrad for being less than a man if he can’t close the deal with a white woman.

Along with Matthew Modine (as a con man whose scheme recalls The Music Man and the Simpsons classic “Marge vs. the Monorail”), Kennedy is the latest addition to a strong supporting cast that has grown large enough to create the danger of Parker being marginalized on her own series. That would be disappointing, but if more shows had that problem, there’d be a lot less bad television.