"A hard apple, a soft orange."

Translation: Twarde jabłko, miękka pomarańcza.

[jruota]

"miękki pomarańcz" is not correct? Only "pomarańcza"?

[immery]

yes standard Polish has "pomarańcza", "pomarańcz" happens in some regional dialects.

[Jellei]

and it's femine anyway, as far as I know - when it means the fruit, of course.

It's also a totally correct and masculine noun for the colour orange.