On November 5, 2007, Showtime ordered 13 new episodes for a fourth season of Weeds. It started on Monday, June 16, 2008 and concluded on Monday, September 15, 2008. The season opener "Mother Thinks the Birds are After Her" was the last episode with "Little Boxes" as the theme song until Season Eight. The opening credits of subsequent episodes, after a recap of previous episodes, begin with a video title card unique to each episode. For the second episode of the season, for example, a highway sign reads "Weeds – Created by Jenji Kohan" — the embedded text used for all title cards since the show's inception. Each title card also has a prop or part of the setting that refers to a plot element in the episode. Some part of the title card morphs into a cannabis leaf. In the highway sign example, a downward arrow designating a lane becomes a slightly larger leaf. Silas and Shane are aged 17 and 13 respectively. However, Silas turns 18 at the end of the season.
Plot
Having lost both her Agrestic grow house and her residence in fires, Nancy relocates her family to the fictional California town of Ren Mar, near the Tijuana-San Diego border. They move in with Andy and Judah's father in Ren Mar. Guillermo hires Nancy to bring illegal drugs from Mexico. She finds out after delivery that her smuggling abilities were being tested — she was transporting legal asthma inhalers. Celia is in jail due to being the official lessee of Nancy's grow house. She bargains to spy on Nancy for the DEA in exchange for her release. Guillermo's men catch Celia spying but Nancy convinces them to spare Celia's life by claiming she was her partner. Andy enters a coyote partnership with Doug, who has recently moved to Ren Mar to evade questions about Agrestic's finances. Isabelle is unenthusiastic about moving from Ren Mar to her father in Detroit and pesters her mother Celia until she lets her daughter stay with her. Silas sets up a grow room in the rear of a gourmet cheese shop owned by a neighbor, an attractive woman in her thirties. Despite knowing that Silas is under 18, she becomes intimate with him. She reveals to Silas that her interests in him are just financial and physical, causing a heartbroken Silas to spurn her advances and to end their business relationship after her ex-husband catches them in the act. Meanwhile, Shane attacks the most popular boy at school without provocation, in order to acquire a fearsome reputation. He also attracts the admiring attention of Simone and Harmony, with whom he loses his virginity in a threesome. Guillermo's boss, whose identity is unknown to Nancy, has her open a maternity store. She believes it is solely for money laundering until she finds a tunnel entrance in the back room. She is told it is for transporting marijuana from Tijuana. Nancy later learns that the tunnel helps transport other controlled substances, as well as guns and women. Shocked, Nancy informs DEA Captain Roy Till, even though she has begun a sexual relationship with Guillermo's crime boss, revealed as Esteban Reyes, Mayor of Tijuana. The resulting DEA raid and shootout ends with most of the Mexican drug runners arrested. While working at Nancy's store, Celia begins abusing the readily-available drugs. Isabelle and Dean stage an intervention, which spurs Celia to enter rehab and make amends to her family. Dean rejects her attempts, insisting that Celia instead locate and make amends with their oldest daughter, Quinn, who departed during the show's inaugural episode for a Mexican boarding school named Casa Reforma. Newly graduated, Quinn and her boyfriend, a self-styled Mexican revolutionary, drug Celia and hold her hostage in order to extract a $200,000 ransom. Esteban captures and intends to have Nancy killed after discovering she had alerted the DEA to his tunnel. After Nancy discloses that she is carrying his child, possibly a boy, he spares her. At home, Shane steals Silas' weed, and Simone and Harmony help him to sell it at school. Doug falls for an undocumented woman he names "Mermex" after witnessing her unsuccessful attempt to enter the United States via the ocean. After much searching, Doug locates Mermex and uses his coyote enterprise to get her into California. Though he expects her to be grateful, Mermex is instead repelled by Doug's unapologetic nature and genital warts. She has fallen in love Andy, now a folk hero known as "El Andy." Scorned, Doug turns Mermex in to immigration. Realizing that poverty effectively prevents him from having to pay any judgments, Doug writes to his estranged wife, daring her to take him to court. In a scene paying homage to The Shawshank Redemption, he then appears to prepare to hang himself, but actually masturbates using auto-erotic asphyxiation. Andy wonders if he is in love with Nancy and questions why he has stayed with the family for so long.
Romany Malco, Tonye Patano, and Indigo do not return, with their characters' whereabouts unknown after the fire in Majestic. In Season 7 Tonye Patano returns as Heylia James for a 4 episode arc.
