  Horticultural enterprises are becoming more sophisticated as the range of the
crops they target expands. Requirements for enhanced efficiency and
productivity have driven the demand for automating on-field operations.
However, various problems remain yet to be solved for their reliable, safe
deployment in real-world scenarios. This paper examines major research trends
and current challenges in horticultural robotics. Specifically, our work
focuses on sensing and perception in the three main horticultural procedures:
pollination, yield estimation, and harvesting. For each task, we expose major
issues arising from the unstructured, cluttered, and rugged nature of field
environments, including variable lighting conditions and difficulties in
fruit-specific detection, and highlight promising contemporary studies.
