grammar - How to differentiate between if zero conditional and if first conditional?

If the tree isn't watered, it (will die - dies - would die).

I know zero conditional should be about facts. In the example above I'm confused whether to choose will die or dies.

Answer

Both will die and dies are grammatical.

In normal speech, you would use will die; but in present-tense narrative (for example, in a documentary film) you might hear dies.