AMERS UNITE!

You get it by clicking one of the grey-colored squares off of your farm border, to the north-east. Once you spend way too many coins "buying" it, you then have to collect an absurd amount of rare items you obtain by harvesting thousands of plants, or sent to you as gifts from friends / request help. Finally, after that obscene investment...the harvester does absolutely nothing for you for free. To use the harvester, click on it and a blue skull looking thing shows up on your cursor...if you have 1-10 plants ready to be harvested, you can click this skull on those plants and it will instantly harvest a maximum of 10. It accomplishes the same thing as you clicking on 10 plants and watching your monster harvest them one by one.

A variety of machines show up that you can "purchase the right to quest to build" and each one unlocks at various levels. To have more than one machine, you have to buy another square.

There is a quest to use the super harvester - that should be the only reason to build one.