"Trees are good."

Translation: Stromy jsou dobré.

[LuukSk]

Why is it dobré and not dobrý? Since stromy is also wirh a 'y'

[endless_sleeper]

The adjective has to match the noun in gender, number and case, it doesn't matter what the actual ending is. Sometimes they're the same, sometimes they're not. Check the tips and notes.

[BernardKna]

Please, is "stromy" feminine here? Why not "Stromy jsou dobri" excuse for the accent!

[endless_sleeper]

"Stromy" is masculine inanimate, that's why the endings differ from masculine animate nouns.