Yes. That is a very natural alternative.
Compare the two:
They are close in meaning, but the focus is a little different:
So if you are talking about a task on your to-do list, 観葉植物の水やりをする sounds very natural.
Traditionally, Japanese often uses やる when giving something to plants or animals, so 水やり became the standard fixed expression.
That said, in modern everyday speech, many people also say:
So:
For learners, the safest thing is to recognize 水やり as a standard word meaning watering.
Because in this sentence, 観葉植物 is not being marked as the indirect object of a verb. Instead, it is modifying the noun 水やり through の.
Compare:
観葉植物の水やりをする
= do the watering of houseplants
観葉植物に水をやる
= give water to houseplants
In the second sentence, に marks the target that receives the water.
In the first sentence, 観葉植物 is simply part of the noun phrase 観葉植物の水やり.
Yes, but that is normal in Japanese.
Japanese often leaves out the subject when it is clear from context. So this sentence could mean:
The exact subject depends on the situation.
This kind of omission is extremely common and natural in Japanese.
する is the plain non-past form.
In Japanese, the non-past can refer to:
So context decides the time.
For example:
Yes, it can be.
観葉植物の水やりをする。 is a grammatically complete plain-style sentence.
However, in real life it may also sound like:
Because it is plain form, it can feel a little clipped or matter-of-fact if said by itself. In conversation, speakers often add context or use a polite form such as: