The greenhouse was a building in Plants vs. Zombies Online. It was used to upgrade plants, similarly to the upgrade system in the Chinese version of Plants vs. Zombies 2 . To upgrade plants, the player had to complete certain objectives within the game and have a certain fighting power which depended on what plant was being upgraded. The player could check this information along with the effects of the upgrade by clicking its icon. It was unlocked when the player reached level 5.
- In older versions, only tutorial plants and Ancient Egypt plants could be upgraded.
- In addition, the player had to use Upgrade sun, a special currency obtained through completing levels or daily rewards, to get upgrades.
- Plants obtained in East Sea Dragon Palace could not be upgraded via the Greenhouse.