Questions & Answers about На кусте появился бутон.
Why is it на кусте, not в кусте?
Because the bud is understood as growing on the bush, attached to it. In Russian, на is natural for something located on the surface of or attached to a plant: на дереве, на кусте.
By contrast, в кусте or more often в кустах means in the bush / inside the bushes, among the branches or leaves.
So:
- На кусте появился бутон = a bud appeared on the bush
- В кустах = in the bushes
Why does куст become кусте?
Because after на when it means location, Russian uses the prepositional case.
The noun changes like this:
- куст = bush
- на кусте = on the bush
So кусте is the prepositional singular form of куст.
What case is бутон in?
Бутон is in the nominative singular because it is the subject of the sentence — the thing that appeared.
You can see this from the verb too: появился is masculine singular, and it agrees with бутон, which is a masculine singular noun.