A vertical farming structure having vertical grow towers and associated conveyance mechanisms for moving the vertical grow towers through a controlled environment, while being exposed to controlled conditions, such as lighting, airflow, humidity and nutritional support. The present disclosure describes a reciprocating cam mechanism that provides a cost-efficient mechanism for conveying vertical grow towers in the controlled environment. The reciprocating cam mechanism can be arranged to increase the spacing of the grow towers as they are conveyed through the controlled environment to index the crops growing on the towers. The present disclosure also describes a tower shuttle mechanism that provides operational flexibility by decoupling the loading and unloading operations of the grow towers from the vertical farming structure and, therefore, allowing multiple grow towers to be extracted for harvesting in a batch process before loading new grow towers into the vertical farming structure in a separate process.