Why Citrus ?! I think
Tar would be a much better
Naval bonus/strategic resource (like Stone plays in the game) than Citrus.
Tar
Bonus Resource
Requires Astronomy
Found in Forest tiles
Allows construction of Tar Kiln; Requires Astronomy, +5 XP for Naval Units built in the city, +1 Merchant slot. City must have a nearby source of Tar. Upon discovering Electricity, the Tar Kiln becomes obsolete.
Historical Info:
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest user was the Royal Navy. Demand for tar declined with the advent of iron and steel ships.
Tar kilns (Swedish: tjärdal, Danish: tjæremile, Norwegian: tjæremile, Finnish: tervahauta) are dry distillation ovens, historically used in Scandinavia for producing tar from wood. They were built close to the forest, from limestone or from more primitive holes in the ground. The bottom is sloped into an outlet hole, to allow the tar to pour out. The wood is split to dimensions of a finger and stacked densely, and finally covered tight with dirt and moss. If oxygen can enter, the wood might catch fire, and the production would be ruined. On top of this, a fire is stacked and lit. After a few hours, the tar starts to pour out, and continues to do so for a few days.