When will my crops be ready?

With 5.1 this actually changed to be relevant to your region. Crops will grow when the dailies on your server reset.

• North America: 3am PST
• Oceanic: 3am EST
• Europe: 3am CET

Crops now have a debuff which shows a timer of how long is left before their state changes from "Growing" to "Ripe" (or Plump). Since patch 5.1, this is synchronised with the daily quest reset timer. Therefore your crops will finish growing at the following times;

• US realms: 03:00 PST
• EU realms: 03:00 CET
• Oceanic realms: 03:00 Australian EST

This portion of post contains outdated information relevant to patch 5.0

Your crops will become ready for harvesting at midnight server time - this means that regardless of the time of day you plant your crops (including 11:59 server time), your crops will be ready at midnight.