Gems are a currency in Plants vs. Zombies Adventures. They are purchased with real money, and can be converted to the various resources at a predetermined ratio and used to negate wait times for constructing or upgrading buildings, as well as purchase already-grown plants, and unlock or use some decorations to the Player's Town.
The player starts with 100 free gems, but if they want more, they must buy them with real money, earn them in Brainball, or earn them from occasional gem give-aways.
There are six possible packages for Gem purchases.
Gems are also in Plants vs. Zombies 2. They are dropped randomly by zombies with an unknown chance. They are mainly used for the Zen Garden, for speeding up plant growth time and adding new pots or for boosting up plants in the seed selection screen.