Abstract In order to detect phytoncide or aroma in a natural environment using an odor sensor of quartz crystal resonator (QCR), the authors investigated the most suitable drying agent to eliminate moisture influences. The odor sensor used is a system of QCRs coated with organic sensory films. It was experimentally found that calcium chloride is the most suitable desiccant for odor sensing to eliminate moisture influences and for use in the natural environment. We then measured 6 kinds of roses; Love (red), Star light (yellow), White Christmas (white), Snow white (white), Catherine Deneuve (pinky orange), and First love (pink), to detect the aroma of these naturally cultivated roses in an outside garden. We have successfully detected the aroma of roses by eliminating moisture influences on the odor sensor by using a calcium chloride desiccant tube. It was found that White Christmas, Star light, and Catherine Deneuve indicate a similar pattern and Snow white, First love, and Love indicate another similar pattern. It was concluded that the odor similarity is not corresponding to the color of roses.