Pacific Coast Iris

Botanical Divas of the Garden

By: Kathleen Sayce
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Kathleen Sayce is an ecologist with a M. Sci. in Botany from Washington State University. She is a board member…

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A rainbow of blossoming Pacific Coast iris in spring. Photo: courtesy of Wild Ginger Farm

A rainbow of blossoming Pacific Coast iris in spring. Photo: courtesy of Wild Ginger Farm

Many in the iris-growing world consider Pacific Coast iris (PC iris) to be divas, gorgeous in flower but relatively fussy compared to tall and hearty bearded, Louisiana, or spuria irises. It’s time for a new mindset. Here on the West Coast, we are in PC iris homelands. Create the right growing conditions in your garden and enjoy their marvelously intricate jewel-toned flowers each spring—a reward well worth the learning curve. The word iris is Greek for rainbow, a description that fits Pacific Coast iris beautifully.

Flowering clump of Iris tenax. Photo: Elyse Hill

Flowering clump of Iris tenax. Photo: Elyse Hill

I acquired my first Pacific Coast iris after encountering wild Iris tenax in flower on a hike. I purchased several plants at regional nurseries featuring native plants and most of them thrived. In my dry gardening practice, I grow plants with no supplemental summer water in a mix of full sun to part shade. My early—and largely accidental—success with PC iris was the result of my southwest Washington garden (zone 8) providing optimal conditions: acidic well-drained soil, wet in winter, dry in summer, and partial shade. Deer occasionally mouth new plants but otherwise leave them alone. The tough, evergreen plants produce their delicate flowers in a broad range of colors.

Like all irises, PC iris flowers have large, downward arching falls, upward to upright standards, and prominent style arms. These can all be one color, or all different, with various amounts of veining, ruffling, and other patterns. Falls may be a solid color or have a prominent signal (blotch of one or more colors), along with edge colors, halos, streaks, and other markings.

PC iris ‘Ocean Blue’: light blue with dark blue veins and yellow signal. Photo: Ken Walker

PC iris ‘Ocean Blue’: light blue with dark blue veins and yellow signal. Photo: Ken Walker

Like other plants that are particular about their growing conditions—think rock garden or bog plants or terrestrial orchids—PC iris can be drama queens, dying quickly when conditions are not to their liking. They do not tolerate waterlogged soil, standing water, hot humid summers, hot roots in bone-dry soil, or hard frozen soil and frozen roots. Being upland plants (not wetland plants), they require well-drained, acidic soil and prefer to have cool roots in summer and unfrozen roots in winter; amending with compost and topdressing with a woody mulch helps create these ideal conditions.

PC iris 'Amethyst Cloud'  Photo: Emma Elliott

PC iris ‘Amethyst Cloud’ Photo: Emma Elliott

In coastal gardens, PC iris grows in full sun. Gardeners in warmer southern and interior regions should furnish more shade as the climate gets hotter. If soil drainage is excellent, PC iris tolerate summer water. Deep mulches or snow cover protect plants in colder regions (zones 5–6), or gardeners may grow the plants in large pots, moving them into a greenhouse where temperatures remain below 55°F for the winter.

PC iris resent transplanting when roots are not in active growth. Plant while new roots are forming in early to mid-spring before flowering, or in the fall. In mild winter regions, plants can be planted or moved fall through spring. In hot climates, either fall or spring may be more successful.

When my collection of PC iris grew to 20 varieties, I began learning more, starting plants from seed, taking trips to see species in the wild, and visiting gardens that featured PC iris. Yet in the iris world, I’m just getting started. Enthusiastic irisarians count and collect iris varieties in their gardens by the hundreds. These plants are well worth the effort to grow. If you practice low-input gardening, pay attention to soil amendments, and live where summers are not too hotand winters aren’t too cold, give PC iris another try or two.


PC iris 'Premonition of Spring' Photo: Garry Knipe

PC iris ‘Premonition of Spring’ Photo: Garry Knipe

Get Growing

The Society for Pacific Coast Native Iris (SPCNI) advances the study and cultivation of Pacific Coast iris. SPCNI maintains a registry of hybrids and hosts an annual online seed sale for members. SPCNI also posts descriptions of species and information about growing PC iris. www.pacificcoastiris.org.

Species Iris Group of North America (SIGNA) includes PC iris in its annual seed sales, and has photos of several species and  hybrids in the online iris species gallery. www.signa.org.

American Iris Society (AIS) includes PC iris species and hybrids in an online iris encyclopedia; each entry includes photos and descriptions. This encyclopedia is quickly becoming the go-to place for online information on iris species and hybrids. For more information see www.irises.org.

Many nurseries in the west offer at least a few plants, and many nurseries offer several registered varieties and  their  own seedlings, including:

Leonine Iris Nursery, Seattle, Washington, www.leonineiris.com

Cascadia Iris Gardens, Woodinville, Washington, www.cascadiairisgardens.com

Wild Ginger Farm, Beavercreek, Oregon, www.wildgingerfarm.com

Bay View Gardens, Santa Cruz, California

Matilija Nursery, Moorpark, California, www.matilijanursery.com

A number of seed companies offer seeds of one or more species; many of these are unregistered hybrids. Plants are available at many iris nurseries and native plant nurseries. An annual list of those nurseries offering more than 4 species and 10 registered hybrids is printed in the SPCNI publication, Pacific Iris.