FarmVille and Zynga have either on purpose or accidentally added in the Sartre Guava Tree sinto Mystery Seedlings! You can start growing up those seedlings now to maybe get a hold of these guys

We think these will actually be released around Monday. For the time being, the trees do not appear on your farm but show as a gray place holder.

Sartre Guava Tree Mastery Requirements & Rewards :

Mastery Level 1: 75 harvests / Rewards: 25 XP and 500 Farm Coins
Mastery Level 2: 150 harvests / Rewards: 75 XP and 1,500 Farm Coins
Mastery Level 3: 225 harvests / Rewards: 250 XP and 5,000 Farm Coins