Iris, a common garden flower, also has natural relatives. In Estonia, these include the Siberian iris and the yellow iris. Both have very beautiful large flowers. The flowers of the Iris sibirica are blue; those of the yellow iris, however, are yellow. As another difference, the leaves of the Siberian iris are very thin (only about half a centimetre). The leaves of a yellow iris, however, are wide (1–2 cm). The flowers of Siberian iris have a tender smell, but those of the yellow iris do not smell at all. The rhizome of irises is large and strong. It can be used to make black dye, which is toxic and corrosive. Therefore, fresh rhizomes and roots of irises cause severe inflammation in the mouth and throat. The poisonous substance decomposes upon drying. The seeds of the yellow iris have a bitter taste, which is why they have been added to coffee in desperate times. The Siberian iris usually grows in large bushes in humid places. Under protection (protection category III).