While bearded iris are the most common in the garden, the Siberian iris is a close second. Hardy and easy to grow, this perennial is smaller and more delicate than its furry cousin and does not have the fuzzy "beard" that gives bearded irises their name. Siberian iris come in shades of purple, blue, pink, white, yellow, and wine-red. The foliage of the Siberian iris is upright and grasslike, and flowers bloom on tall stems in late May or June.
Siberian iris like moist, well-drained fertile soil and full sun or partial shade. They prefer an acidic soil with a pH of 5.5 to 6.9. They will still perform in poor, dry conditions. Plant Siberian iris in the spring or late summer. Amend the soil with compost, peat moss, or other organic material if desired. In hot climates, make sure to plant your Siberian iris in an area that receives some shade during the hottest part of the day.
Plant groups of three to five, or more, of the same variety for the best visual display. Before planting, soak the rhizomes in water overnight. Siberian iris should be planted deeper than the bearded variety. Plant each rhizome so that it is covered with one to two inches of soil. Space plants 18 to 24 inches apart. Be aware that Siberian iris seldom bloom the first year after planting and won't come into full bloom until their third or fourth season. Siberian iris are a good choice for naturalizing around a pond or other water feature. They are also a good backdrop for a border, growing 2 to 4 feet in height.
Water your Siberian iris well the first season, especially during hot dry weather when weekly watering may be required. Keep the soil moist during the spring.Continue to water regularly throughout the entire first growing season. Once established, water weekly during hot weather. Established clumps should be fertilized in early spring and immediately after blooming with a 10-10-10 general purpose garden fertilizer. Use two to three inches of mulch around established plants to lock in moisture and prevent the growth of weeds. Cut back dead leaves and stalks in the late fall or early spring and dispose of the debris. Mulch heavily during the winter for best protection.
Siberian iris are relatively disease and pest free, unlike their bearded cousins. Sometimes an iris will exhibit stunted growth and foliage that resembles corrugated cardboard. This condition is not serious and will not kill the plant. It is called "pineappling" and is not contagious to other plants. New growth will normally come in healthy. Pineappling is believed to be the result of abnormal weather conditions.