Rumors are spreading about Bernadette having thoughts of terminating her relationship with Howard while Howard is thinking of proposing to her. Sheldon and Amy spread their own rumors to test a theory.
At a book store Brian Greene is promoting his new physics book: The Hidden Reality, where he attempts to present complex physics issues in a manner understandable to non-scientists. Included in his audience are Amy and Sheldon who find his explanations hilarious. As they listen to his presentation, Amy tells Sheldon a piece of gossip she got from Penny: Bernadette is thinking of breaking up with Howard.
The following day, Leonard and Sheldon are playing Wii Sports: Archery in their apartment. Sheldon brings up his discussion with Amy, passing on the piece of gossip to Leonard. He eventually tells Priya (while explaining how Sheldon requires people to stand away from the mirror when flossing) who mentions that Raj has a crush on Bernadette and would be happy if Bernadette went ahead with it.
Leonard runs into Penny in the apartment building lobby and tries to pass on the gossip only to find out that she was the root source of the gossip (though she obliviously blames Amy for being the root source of the gossip and complaining about Amy's inability to keep a secret). Leonard follows it up with informing Penny about Raj's crush on Bernadette and noting how it could lead to the end of Howard and Raj's friendship. Penny promises to keep this news secret. Meanwhile, Priya implicitly tells Raj about Bernadette while they're on a video conference with their parents while Priya continuously tries to prevent Raj from telling them about her relationship with Leonard.
At lunch in the university cafeteria, Howard tells the gang that he's planning to ask Bernadette to marry him. As he disappears to discuss the wedding ring with his cousin, the rest of the gang express their concern, or in Raj's case, excitement, about the heartbreak he'd get if he tried to ask Bernadette to marry him, only to have her break up with him.
Sheldon and Amy are having drinks in Sheldon's apartment discussing the news that Howard is going to propose to Bernadette. The general interest that the topic had created among their social circle intrigues the pair and prompts them to begin experiments to study meme theory. To begin their experiment, Amy tells Penny that she and Sheldon had sex and that she was thinking of starting an herb garden. Penny tells Raj about Amy and Sheldon after she catches him at the The Cheesecake Factory hitting on Bernadette.
Later, Leonard brings home dinner and starts trying to mine Sheldon for information about his relationship with Amy, mentioning off-handedly that he'd just spoken to Raj. Sheldon deflects the questioning, though he provides a few inquiries to ensure that Leonard was discussing the rumors about sex and not the herb garden. After Leonard heads to his room, it's revealed that, during that time, Amy was listening to the conversation via Sheldon's computer. They express surprise at how quickly the information was propagating through the group. By the time dinner happens, Amy has determined that the piece of gossip is known by everyone in their social group, taking less than 24 hours to reach everyone. At dinner, Howard decides to propose there and, to everyone's surprise, Bernadette accepts. Everyone is happy for them except Raj who is crying and disappointed.
In a follow-up experiment, Amy tells Penny she's pregnant with Sheldon's child and she is getting orthotics. As she walks down the stairs, she runs into Leonard who had just received a text from Penny passing on the news, to his astonishment.
- Guest starring:
- Teleplay: Bill Prady, Steven Molaro & Steve Holland
- Story: Chuck Lorre, Eric Kaplan & Eddie Gorodetsky
- The TV Critic: "The expansion of the gang to include Amy, Bernadette, and Priya has been a huge boon for the show. Suddenly all four of the guys had an emotional involvement in the unfolding story and I don't remember many occasions when that was true... The producers seem to have embraced the need for recurring characters and ongoing stories and the results are very encouraging. I felt engaged for the whole episode and amused by almost everything. If the writers can inject a touch of real emotion into the inevitable breakups coming then I will be hugely impressed."
- The A.V. Club gave this episode a B-.
- IMDb user reviews
- Title Reference: Amy and Sheldon spread rumors including one about an herb garden to test a theory.
- Chuck Lorre's vanity card.
- This episode was watched by 11.40 million people with a rating of 3.7 (adults 18-49).
- This episode aired in Canada on April 7, 2011 with 3.219 million viewers and a weekly ranking of #1.
- In the United Kingdom, this episode aired on August 18, 2011 with 1.237 million total viewers and a weekly ranking of #15.
- Episode transcript 
- Leonard wears his Ames Brothers "Wisdom" shirt as well as his radiation emblem olive green shirt from CafePress.
- Sheldon wears a Green Arrow bullseye shield logo t-shirt.
- This is the only time Raj, Priya and their parents share a scene together.
- Bernadette's full name, Bernadette Maryann Rostenkowski, is revealed for the first time.
- Brian Greene's real book, The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos, was published on January 25, 2011 and there was a book event with Dr. Brian Greene the next day.
- Sheldon asks Brian Greene why he doesn't do something more useful than educating the general populace about scientific ideas, and suggests reading non-Greene books to the elderly. He finds how Dr. Brian Greene "dumbs down Werner Heisenberg for the crowd" hysterical. Similarly, in "The Luminous Fish Effect", Sheldon states Eric Gablehauser has "done no original research in 25 years, and instead [has] written a series of popular books that reduce the great concepts of science to a series of anecdotes, each one dumbed down to accommodate the duration of an average bowel movement." Leonard also pointed out to Sheldon, "Well, you did call [Gablehauser] a glorified high-school science teacher whose last successful experiment was lighting his own farts."
- Sheldon says, "Now I’m thinking about the origin of the phrase train of thought. Now I’m thinking about trains." He similarly provides homophonic connections in "The Luminous Fish Effect" ("luminous" and "loom") and "The Bad Fish Paradigm" ("tick" and "tic"). In the latter, he incorrectly refers to a homonymic relationship.
- Sheldon wears a leather two-finger archery shooting glove, just as he wore a bowling wrist guard in "The Bath Item Gift Hypothesis", just to play Wii Sports. In "The Bat Jar Conjecture", he cited an old Nintendo injury, and he referred to Penny deserving carpal tunnel syndrome in "The Dumpling Paradox" after playing Xbox 360.
- In apartment 4A, there are two pieces of tape on the floor in Leonard and Sheldon's bathroom. One is in front of the sink and people must brush and floss their teeth from behind this piece of tape. A second piece is in front of the toilet for those that stand up to pee, though what exactly it marks is not specified.
- During school, Sheldon was teased with the line "Shelly Cooper is a smelly pooper". Raj later references this line to Penny.
- At the end of the episode, the gang thinks that Sheldon and Amy have been having coitus and that Amy has a bun in the oven.
- Priya urges Leonard to let her see The Roommate Agreement, which plays a part in the next episode, "The Agreement Dissection".
- Also in the next episode, Amy mentions she recently trained a Capuchin monkey to smoke cigarettes. This monkey, named Ricky, appears in Amy's apartment.
- When Leonard and Penny talk about Raj's "love" to Bernadette, Leonard says, "Well, the point is, if this got out, it would destroy Howard and Raj's friendship." Ironically, later in "The Skank Reflex Analysis", it is Leonard who reveals this to Howard, causing turmoil among Howard, Bernadette and Raj. Leonard reveals this fact by citing Raj's poem "O Bernadette, please play my clarinet", which is told to him by Priya in this episode.
- Amy's two control rumors are that she is thinking of getting orthotics and that she is planning on starting an herb garden.
- Leonard mentions to Priya that it is easier to just follow Sheldon's rules instead of getting a lawyer, however ironically Priya acts as Leonard's lawyer in the next episode.
- Priya suggests that they have Howard and Bernadette over to dinner. In "The Wildebeest Implementation" she does have them over to Raj's apartment for dinner.
- The title of the episode may be a reference to marijuana culture due to the title referencing 'herb' which coincides with episode #420.
- (Sheldon and Amy have commenced their gossip experiment and Amy has started it by going to Penny's the next day)
- Penny: Oh, hey Amy, what's up?
- Amy: Sheldon and I engaged in sexual intercourse. In other news, I'm thinking of planting a herb garden. Mum's the word--gotta go.
- (Amy dashes off, leaving Penny completely surprised and shocked)
- (After all the rumors and Howard's proposal, Sheldon and Amy have decided to do their experiment again, with Amy back at Penny's to tell her some more juicy news)
- Penny: Oh, hey Amy, Bernadette just texted me, Howard proposed?!
- Amy: Yes, not important. Just stopped by to let you know I'm getting orthotics. Also, I'm carrying Sheldon's baby. Mum's the word!
- (Amy dashes off again, with a shocked Penny about to text on her phone to tell someone the news. As Amy comes down the stairs, she meets Leonard, who has gotten Penny's text. He looks up at her, completely surprised.)
- Leonard: You're pregnant?!
- Amy: Wow. Is there anything there about orthotics?
- (Leonard looks at his phone confused)
- Amy: I’m glad you talked me into this. We work so hard, sometimes, it’s nice to goof off and do something silly.
- Howard: Hey, everybody, I got something I want to ask Bernadette, and I can’t think of a better time than when I’m with all my friends.
- Leonard: Oh, hold on, Howard. There’s lots of better times.
- Raj: Leonard, please. The man is talking. Let him get it out, and let the chips fall where they may.
- Howard: Thank you. Bernadette Maryann Rostenkowski…
- Bernadette: Oh, God. What’s happening?
- Howard: I know things haven’t been perfect with us, and we've had our problems, but I just have to tell you, from the moment I…
- Bernadette: Howard, let me just stop you right here.
- Raj: This is it.
- Bernadette: Yes.
- Howard: Yes, what?
- Bernadette: Yes, I will marry you.
- Howard: You will?
- Raj: You will?
- Bernadette: I will. I will!
- Howard: Oh, I love you so much.
- Bernadette: Oh, I love you, too.
- Leonard: Congratulations!
- Priya: Oh, it’s so exciting.