In Nightcrawler, Louis doesn't do much in his free time. He just watches TV only to see his videos in news and waters his plant with a glass of water. He was shown with no empathy and being too selfish. But he did water the plant whenever he got time. What does this habit trying to represent? Or am I just digging deeper than I should?
Personally, I think they show him watering the plant to indicate how isolated from other people (and humanity) he is. It's the only "relationship" he has, and the only positive interaction he has with another living thing.
But perhaps I'm also reading too much into it? The only direct source I can find is a quote from writer and director Dan Gilroy, where he states that:
All of the scenes inside Lou’s apartment were funneled down to one day. We had to shoot everything there in just one day. Actually, it was less that one day because our schedule got tightened up. So Jake, our director of photographer Robert Elswit and I knew that we had a shoot quite a few things in the apartment, but it wasn’t scripted fully. We knew we needed him watching the TV, but we needed him watering the plants, going to the kitchen, going to the bathroom, that sort of thing.
That quote seems to indicate that they just need some shots of him inside his apartment and what he was doing might have been random. Though, there are a lot of subconscious elements to the creative process, and even if the act of watering the plant was random, it might not have been completely random.
The plant was under his complete control
It was a living thing that was completely dependent on him and its existence was defined by Lou's actions. It was an object that Lou had control over.
As the film progresses we see him, successfully, controlling aspects of other characters such as his cameraman and Nina Romina.
In the beginning of the film he was being written off, by the junkyard manager for instance, as a nobody. Later when he starts get credibility and praise he is able to use that as confidence to get other to do his bidding.
Assuming there is anything to read into the plant I think it was a device to show Lous character and another aspect of how he deals with relationships.
I don't have much evidence to support this, but while watching the film I noticed the plant didn't grow. Like, at all. So I thought, what's the significance of this plant? Then I had the idea, what if the plant is fake? It's a fake plant in place of a real one, being watered. Comparing that to Lou being a sociopath, faking emotions, pretending to be a normal person. I'm not sure, this was just a fun idea, what does anyone else think?