How do you breed the Legendary monster?

There is a quest in the game to acquire the Legendary monster. Description:

Legendary

Find and hatch the mysterious Legendary monster, master of the elements!

If you want to breed it, what combination of monsters do you use?

It has been confirm here and here that breeding Flower and Mountain has a rare chance to produce the legendary monster. The first link involves a screen cap of the park and the second link includes a video, so I'm going to consider this definitive proof. Since this combination is Fire/Plant + Earth/Plant it appears that previous theories about involving all elements are incorrect. You do need to be level 22 to buy the habitat that the Legendary Monster lives in.

You have to be on to level 22 to be able to hatch the legendary monster.

To hatch the monster you have to:

• Be on level 22
• Breed a teenage plant and an adult earth.

Then you will get a legendary monster.