In ICT for agriculture, there are three types of horticulture systems. The first is for collecting and analyzing temperature data in agricultural fields, such as a grape plantation. The second is used for plant factories that continuously produce vegetables, regardless of location or season, in an artificially controlled environment. The third is greenhouse horticulture for raising vegetables, fruit trees, and flowering plants. The third type of horticulture is the method used to grow plants in facilities, such as large-scale greenhouses and easy-tomanage vinyl plastic hothouses, by adjusting temperature, sunlight and so on. It requires many small sensors with lowpower consumption and stable communication with the data collectors. The number of data collectors is expected to be low for cost-effective system configuration. We propose a long-haul reliable sensor network to manage greenhouses and hothouses, taking advantage of the 400MHz band and semi-dynamic channel management. The effectiveness of WSNs is evaluated through their actual use in greenhouses. This paper concludes with our plan to evaluate the 400MHz WSN with large-scale WSNs.