Carline thistle is a natural hygrometer. During dry sunny days, the petals are spread out. If the air is humid, the petals start to curl up and if it rains, they form a dome over the heart of the flower. Carline thistle makes a very good dried plant. In fact, it is someitmes more obvious in the winter when all other growth is less prominent. The dried stems and flowers often remain upright till the next spring. Even in the winter the plant still acts as a hygrometer. Carline thistle is popular among songbirds such as linnets and goldfinches and various insects.