This repository provides the complete design and firmware for the Smart Plant, an ESP32-S2 based IoT device for monitoring soil moisture, ambient temperature, humidity, and illuminance. The firmware, built on the ESPHome framework, publishes sensor data to Home Assistant via MQTT and displays it on a 2.9-inch ePaper screen. It employs a sophisticated deep-sleep architecture to achieve 40-50 days of battery life, with careful power management of sensors and MQTT connections. The architecture is centered around a highly modular ESPHome YAML configuration. The `examples/multi-device/packages/smart_plant_base.yaml` file serves as a reusable base package, enabling fleet management through YAML substitutions and overrides. This pattern allows users to deploy multiple devices with a shared core configuration, customizing only device-specific parameters like MQTT topics and sensor calibrations. The data flow is strictly sensor-to-cloud, with retained MQTT messages ensuring Home Assistant entities remain available during the device's deep sleep cycles. Beyond firmware, the repository encompasses the full hardware design. The PCB is designed in Autodesk Eagle, and the 3D-printable enclosure is provided in both FDM (STL) and SLA (STEP) formats, originating from CATIA. The project is accompanied by professional Sphinx documentation hosted on ReadTheDocs, including assembly guides, safety information, and programming instructions. Overall, this is a high-quality, production-ready IoT project. The ESPHome base package is a standout reusable component for anyone building battery-powered ESPHome sensors. The hardware designs are complete and manufacturable. While the documentation contains minor copy-paste errors (e.g., referencing 'Smart Powermeter') and mixed-language comments in the YAML configs, the core firmware architecture and hardware design are exceptionally well-executed.