Traditional farming is often affected by unpredictable environmental hazards, such as cold or hot weather, typhoons, flood, and drought, and requires considerable labor. To overcome such difficulties, we developed a web-based crop system to monitor and control environmental parameters such as air temperature, air humidity, sunlight intensity, and soil moisture. The system also operates sunlight-blocking curtains, ventilation/cooling fans, water sprayers, and an alarm on the basis of preset values of the parameters or manually online. The monitored parameters are shown on a mobile device through a low-cost open-source IoT platform (NodeMcu). The programs for operations are created in C# and JavaScript. The proposed system helps users grow crops in greenhouses efficiently by controlling the environmental parameters and necessary facilities remotely.