The Herb Garden Germination

The Herb Garden Germination is the twentieth episode of the fourth season of the CBS sitcom The Big Bang Theory. It first aired on April 7th, 2011.

Plot Summary
Rumors are spreading about Bernadette having thoughts of terminating her relationship with Howard while Howard is thinking of proposing to Bernadette. Sheldon and Amy spread their own rumors to test a theory.

Extended Plot
The episode starts with Brian Greene 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 to be 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 Archery on the Wii when Sheldon brings up his discussion with Amy, passing on the piece of gossip to Leonard. Leonard 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 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, Howard tells the gang that he's planning to ask Bernadette to marry him. As he disappears to discuss the 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 amongst 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 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 supper happens, Amy has determined that the piece of gossip is known by everyone in their social group - taking less than 24 hours to have reached everyone. At the same supper, Howard decides to propose there. To everyone's surprise, Bernadette accepts the proposal.

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.

Quotes
(Sheldon and Amy have commenced their gossip experiment. Amy has started 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.)

Trivia

 * 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. Greene the next day.
 * 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.
 * 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 was 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 urged Leonard to let her see the Roommate Agreement, which plays a part in next episode.
 * Amy mentions she recently trained a capuchin monkey to smoke cigarettes. This monkey, named Ricky, appears at Amy's apartment in the next episode.