These iris thrive in the marine coastal climate, with dry summers and cool, wet winters. Plants are very prolific and grow readily from seed. Transplanting, however, can be difficult. They are best moved or divided in the early fall, when root growth is active and can continue well into winter. Plants can also be moved prior to spring bloom.

Transplants must be kept well watered until natural rainfall can maintain high soil moisture. They should be heavily mulched with bark dust, pine needles or leaves, to prevent frost damage to newly developing roots. Once established, plants are usually tolerant of normal freezes and periods of drought. If frost damage occurs to leaves, wait until well into spring to watch for signs of new growth. PCNs should receive at least a half a day of sunshine.

These irises bloom after the Tall Bearded. They prefer full sun and ordinary garden conditions, but require ample moisture, especially up to bloom time. They will do very well beside a stream or a pond but in cold climates they do not like to have their roots in water during the winter. Japanese iris prefer a heavy, rich soil with ample organic matter. The soil pH should be slightly acid, ideally between 5.0 to 6.5. They do not like lime, so do not plant close to cement, as lime leaches out of it.

Plant strong divisions of 2-3 fans. The roots should never dry out during transplanting. Plant the rhizome 1-2 inches deep, preferably in a 3-4 inch depression, which will catch and hold moisture. Since new roots form above the old ones, soil may be gradually added to fill in the depression over 3 years or so, to maintain plant vigor for a longer period of time. Keep division well watered after planting, until established. Japanese iris are heavy feeders. A liberal application of a balanced fertilizer, such as 12-12-12, in the early spring and just after bloom is helpful.

Transplanting may be done from spring until fall but shortly after bloom time is best. This gives the new roots time to anchor the plant before winter freezes. A heavy 2-3 in. mulch is beneficial to conserve moisture and reduce weeds. If plants are set out in fall, mulch heavily before the winter.

Siberians are a hardy beardless iris growing from 2-4 ft. in height. They bloom at the end of the tall bearded season. They are very effective in naturalized settings and perennial borders. Siberians perform best in full sun, but can tolerate less. Good drainage is critical. Siberians like year round moisture, but not soggy conditions. They should be kept moist during spring. A light fertilizing in the spring and again after bloom encourages strong growth and good bloom.

Newly purchased or received Siberian rhizomes should be soaked in water overnight before planting. When planting, cover the rhizomes with 2-3 in. of soil, spacing plants about 2 ft. apart. Siberians like acid soil, which may be enhanced with peat moss, compost or other humus. New plants should be kept well watered.

When the foliage dies back in the fall it should be cut off close to the ground and removed from the garden. Siberians need 2-3 years to become fully established; the first year's bloom is not representative.

These iris bloom after Tall Bearded but before Japanese iris. They are at home in a wide variety of soil types, but prefer acid soil and boggy areas with at least half a day of sun. They can be grown in regular perennial beds, with additional water during the growing season. Under ideal growing conditions Louisiana irises are robust growers.

Transplant Louisiana's from August to September to allow growth to be established before winter. Plants should be spaced at least 2 ft. apart, with the growing tip facing in the direction you want them to grow. Plant rhizomes horizontally with about 2 in. of soil covering them and water until established. If planted in a triangle, they can be left in place 2-3 years without becoming overcrowded. Ample quantities of organic matter (peat, compost or manure) along with a balanced fertilizer help these heavy feeders. A foliar feeding every 10 days, plus ample water, is helpful in short season areas like Seattle, to get vigorous, uninterrupted growth during the entire season. Mulch heavily before cold weather sets in.

These iris display open, delicate blooms atop tall, rugged plants about 1-2 weeks after the Tall Beardeds. Spurias grow well in all types of garden soil, preferring neutral to slightly alkaline soils. Full sun and good drainage are imperative. They do not like wet feet.

When planting, cover the rhizomes with 2 inches of soil. Space plants at least 2 feet apart. After planting, water in well and water regularly until plants are established. In future years, the plants need water before bloom, but there is no need to water after blooming, although doing so won't hurt them. An application of composted manure or commercial fertilizer will enhance growth. Do not expect peak performance until the second or third year. Spurias should be left alone for years, allowing the plants to grow into the large clumps for which they are noted.

Sino-Siberian irises

Cal-Sib irises are the products of crosses between two iris species, Pacific Coast (Californicae) and Sino-Siberian. The Pacific Coast iris grows within a very limited range in the northwestern U.S. (west of the Cascade Mountains). Crosses with Sino-Siberian iris were made to capture the beauty of the PCI flower on a plant that can grow in a broader range.
Cal-Sib irises are generally shorter than garden Siberian iris, but taller than PCIs. The foliage is semi-evergreen, and flowers are 2-3" in diameter. They grow best when planted in rich, well-drained soil under sun or part shade. Since they are a species cross, these plants are sterile (although you never know what Nature will do...)