Built in a Small Construction Site.
MAKE SURE YOU DO NOT HAVE PUBLIC- OR GUILD-OWNED BUILDING ENABLED WHEN YOU BUILD.
Needed for the Test Of The Plantation.
According to the ENN chat detailing the test, the Headquarters must be built no closer than 2000 feet (~125 coords) from Chariot Stops, and cocoa seeds must be planted within 1000 feet of the Headquarters. If you try to build it too close to a Chariot Stop you will get a message when trying to select "Test of the Plantation" from the construction site's projects menu that says, "Plantations must be far from Chariot Stops"
There is also a minimum distance between any two plantations. Guessing 2000 feet, also, in order to make sure cocoa plants register to the right plantation. - Nefer-Bast
When a cocoa plant is torn out (utility->tear down option), no seed is returned and is lost. The cocoa plant stays in the Plantation inventory and you can not plant another. -Abudabu.
To be clearer, the tree continues to count against your limit and is NEVER reset. You can only gain new trees towards your limit with perfect tends of the trees you have remaining. - Aperio