When is 的 used with adjectives?

的 is a character that implies possession, but can also be used with disyllabic adjectives (adjectives that are two characters long.) For example: 红花 = red flower. 的 is not needed here because the word for red is only one character. However, to say clean bedroom (干净的卧室)， 的 is needed because clean （干净）is two characters long.