Orris root, the sweet smelling component of many perfumes, has been used since the time of the Egyptian pharaohs. Technically it is the rhizome of the iris but if you try sniffing your iris rhizomes next time you are dividing them, you won’t smell anything. That’s because it needs to be dried for at least two years and, in some cases up to five years, to develop its characteristic violet scent.
In the past, orris root has been used medicinally, in snuff and chewed to cover bad breath. In modern times, we use it as a fixative in potpourri and in many perfumes. Orris root is used to flavor gins such as Bombay Sapphire and Magellan. The flowers are used for color and flavor in those gins.
The rhizomes from three iris varieties are commonly used to produce orris root powder and essential oils. Iris germanica (bearded iris), which contrary to its name is not from Germany, in its original form sports a dark purple flower. Iris enthusiasts have bred bearded iris to produce flowers in in every color except true red. Iris pallida, which is native to the Dalmatian coast in Croatia and was probably the iris used to produce orris root powder by the ancient Greeks, has a lavender flower. Iris florentina, a variety of Iris germanica, is found in the area of Florence, Italy which was and continues to be a center of orris root production, is characterized by a pale purple almost white flower. It is the iris most often used for orris root.
Bearded iris including Iris florentina can grow to a height of 4 feet. Iris pallida, a smaller variety, grows to a maximum of 30 inches.
Bearded iris are easy to grow in your garden. They are hardy to zone 5. Iris require full sun and well-drained soil. The rhizomes should be planted so that the top half of the root is above the soil. If they are buried completely in the soil, they will rot. The roots which grow out of the sides of the rhizomes anchor them into the soil and prevent the plants from falling over. The rhizomes should be planted in the summer or early fall. The latest that you should plant them is 6 weeks before your first frost to give the roots a chance to become established before the plant goes dormant for the winter.
Bearded iris prefers to be dry so you should be careful to not over-water them. They do not require a lot of fertilizer. You can scratch in a little compost around the rhizomes. Alternatively, you can use a 6-10-10 fertilizer in the spring before your iris bloom and then again about a month after they finish blooming.
Iris are very hardy plants, not subject to as much disease as some the more delicate garden plants. Spacing helps keep them healthy also. Plant your rhizomes one to two feet apart to avoid crowding which can encourage disease to take hold among your plants. Their biggest enemy is the iris borer. Please click on the link to go to an article I wrote on Hub Pages on controlling iris borer in your garden.
Like any perennial, iris should be divided every 3 to 4 years. Division should be done after the plants finish blooming to give the roots the maximum amount of time to become established before winter. However, if you are growing iris for orris root, the rhizomes should be dug up in the fall. Iris reach maturity in three years, so you want to wait at least that long before harvesting them. Once you have dug the rhizomes up in the fall, you should store them in a single layer in a dry, well-ventilated space that does not get any sunlight. Rhizomes should be dried for at least two years. They are ready to be used when they are thoroughly dry and smell of violets. You can grind them up for orris root powder or distill them for their essential oil.