“There is no potted plant by the entrance... I figured it was about time I chimed in with something.”
Potted Plant (植木, Ueki) is the forty-ninth chapter of the Death Note manga series.
If the Kira killing of criminals stops then the Kira Task Force can only conclude that Higuchi is Kira. However, L and Light realize that without Higuchi showing how he kills as Kira then arresting him will be meaningless. Nevertheless, Light tries to persuade L to detain Higuchi now because otherwise he will pressure Misa into committing murder in order to prove that she is the Second Kira and kill her when she fails to do so. (Light and L are unaware that Misa has already deceived Higuchi with Rem's help.)
L hesitates since he does not want to repeat the events surrounding Light's own detention when the case for him being Kira was weakened. On the other hand, Higuchi's profile indicates that he is hardly of the same caliber as Light Yagami.
L calls Wedy who has been busy installing bugs and cameras in the homes of the Kira suspects. L tells her to focus solely on Higuchi. He's recently reinforced security in parts of his house which will make it difficult to obtain footage from bugs and hidden cameras, but Wedy agrees to install them in all of Higuchi’s cars.
L again raises his suspicion that Light was Kira but passed his powers on to someone else and then forgot all about being Kira. He then asks Light to consider if the transfer was made by his own free will or via a third party. Thinking carefully, Light concludes that it would have been done by his own free will. If a third party was in control they would not have waited until after Light's imprisonment before passing the power on. To know of his imprisonment, short of being a member of the Kira Task Force, the third party would have been watching events from the heavens and would have killed L ages ago. (At this stage neither Light nor L are aware of the existence of the Shinigami or of their rules and limitations.)
L says that their task now is to find a way to make Higuchi show them how he kills, but without transferring his powers to someone else. He figures out a plan in which Matsuda will go on Sakura TV and threaten to reveal the identity of Kira. Sakura is a tabloid television channel whose recent reports, even on the Kira affair, are so blown out of proportion that few people believe what they say. However, if a guest was to reveal facts known to Higuchi to be true then he will have to take it seriously.
Higuchi will remember Matsuda as "Matsui", the nosy manager of Misa Amane who might have overheard a secret meeting of the Yotsuba Kira Group. Higuchi will try to kill Matsui but then realize that it is a false name. Higuchi will call Misa whose cellphone will be turned off and thus not be pressured into killing Matsui or revealing his real name. He will then try and contact her current "manager", Mogi, who will claim to be away from Tokyo and not know "Matsui"'s real name either.
Then, Higuchi will try to call Misa's agents, Yoshida Productions, where the manager will tell him that "Matsui's" CV contains his real name. Since it is late in the evening and the staff are away, Higuchi will have to go to the office himself, get the key from the potted plant next to the entrance and, once he has the CV, show his method of killing, which will be caught on cameras set up by Wedy.
The main problem is preventing Higuchi from passing his killing power on to a third party or even sending that person to the office in order to pick up the CV, but L doubts that he would want to involve outsiders since this could raise questions and time will be of the essence since he has to kill "Matsui" before he reveals his identity on television.
There is also the possibility that Higuchi has the power of the Second Kira: The ability to kill just by seeing a person's face, but given the fact that Matsuda is still alive after faking his own death this looks unlikely since Higuchi would have used his killing power on him afterwards as a precaution.
If there is a single flaw in the plan then Matsuda will die. L says that they will wait to see if the Kira killings really stop and give Matsuda time to think it over. However, Matsuda announces that he is prepared to go along with the plan.
Ohba said the chapter's title "Potted Plant" was used to "mess with the fans." It quite likely relates to when Misa, who knows the Yoshida Productions offices, points out that there is no potted plant outside in which to place a key. Ohba wondered why his editor approved the title, simply saying that he liked it.