The Irises Have It : The Coastal Species Are Strikingly Beautiful and Have a Long Blooming Period

Wallace Moore likes to tell the story about a visitor to his San Juan Capistrano garden who thought the flowers on display were so perfect that they must be plastic.

Although the visitor was being facetious (he was a professional arborist), his comment is indicative of the striking beauty of Pacific Coast Native irises, referred to by horticulturists as PCNs.

PCNs are part of a large category of beardless irises, so designated because they lack the beard, which looks like a caterpillar, that grows on the petal-like sepals of bearded irises.

These iris species are native to the Pacific Coast regions of Washington, Oregon and Northern California. Although there are 11 species within this group, hybrids broaden the range of colors and patterns. These hybrids are unnamed and are relatively rare in home landscapes, although some specialty nurseries offer them for sale, and landscape designers who incorporate native and drought-tolerant plants into their designs are familiar with them.

Carol McElwee, a landscape designer in Capistrano Beach, first saw PCN irises 10 years ago while taking horticultural classes at the Los Angeles Arboretum in Arcadia, she said. A local iris enthusiast had a large planting in his garden, and McElwee was captivated.

“They’re fabulous looking,” she said. “They have such rich colors and patterns. They look like orchids.”

In addition to striking flowers, the plants are characterized by strappy, grass-like leaves. They grow to about a foot tall, with a 2-foot spread.

Since then McElwee has planted more than 100 PCN irises in her garden and includes them in designs where they will thrive.

These irises do best in landscapes where they receive part shade and scant water, said Mike Evans, owner of Tree of Life Nursery in San Juan Capistrano. The wholesale nursery specializes in native plants and sells PCN hybrids of Iris douglasiana, native to the coast from Santa Barbara to Oregon.

“These are among the best of the native plants for low-growing perennial gardens because they mix well with other plants, as long as they have the same water requirements,” he added. “They have a long blooming period of up to six weeks with very showy flowers.”

Flower colors include blue, purple, maroon, copper, brown, pink and white, with intricate veining or patterning. Each clump will produce multiple flowers, with the blooming season starting in February and continuing through April.

McElwee likes to use PCN hybrids for dry shade gardens. In 1994, when Moore enlisted her help in designing gardens for his one-acre site, which included a steep ravine filled with sycamore trees, McElwee put PCN irises at the top of the list.

They planted 150 along the slopes.

Although all grew and bloomed the first year, by the second year, a third of the plants had died.

“They probably died because of over-watering,” McElwee said.

Evans agreed: “They shouldn’t be watered too much. It’s important not to water from the top, like sprinkler systems do, because they are prone to crown rot.”

The plants in McElwee’s garden also have a spotty success rate. “One plant thrives while the one next to it dies, and they both receive the same amount of water. I think some of the hybrids are more vigorous.”

Despite the failure rate, McElwee believes the flowers have a place in native and drought-tolerant gardens and Mediterranean landscapes. “I don’t know why they aren’t used more often,” she said.

McElwee likes to plant PCN irises under trees, especially oaks and pines. It’s hard to find showy, colorful plants that can withstand tree roots and shade. She recommends planting them at the drip line, where the tree canopy ends and digging carefully among the roots.

PCN irises require well-draining, loose soil that is slightly acidic. They also grow well on slopes as long as the soil is porous or well amended. Because the plants are rarely attacked by insects or diseases other than crown rot, they are easy to maintain.

When they like their planting site, the clump will expand and, over time, produce multitudes of flowers.

“Once they are planted right, they don’t have to be fussed with,” McElwee said.

In her garden, she waters her plants by hand for better control and waters only when the soil is very dry.

Evans recommends fertilizing sparingly, at half the rate recommended for typical garden plants.

Although nurseries are stocked with these showy irises in spring, while they are in flower, fall is the best planting time.

Tree of Life Nursery has 1-gallon containers, and most retail nurseries can order them.