Growing Species PCI

Among PCI species there are decided tolerances for sun or shade, more shade, summer dryness or some moisture, and porous, open soils or more clayey soils.

The following notes, by species, summarize what SPCNI members know about growing PCI species, and their most desirable traits. White flowered forms are known for most species, so assume there are white flowers (alba forms) along with other colors listed if white is not mentioned.

Siskiyou Iris, Iris bracteata

This species grows in shady forest locations in Ponderosa pine forests in Josephine County, Oregon and Del Norte County, California. It is a member of the Klamath hybrid complex.

Leaf bases are pink to strongly red, and flowers are yellow with attractive brown to maroon veins.

Yellow-leaf Iris, Iris chrysophylla

A species of shaded, serpentine soils, Iris chrysophylla grows on slopes. Flowers are white to cream to yellow. It is found in open coniferous forest, dry Yellow Pine-Douglas-fir Forest in southern Oregon. It is a member of the Klamath hybrid complex.

It is one parent of the distinctive ‘Valley Banner’ form of a natural hybrid between I. chrysophylla and I. tenax, in which the falls are white with purple veins, style arms are dark, typically purple, and standards are creamy white.

Despite the name, its foliage is not distinctly yellow compared to other Pacific Coast irises.

Douglas Iris, Iris douglasiana

The most moisture tolerant, and sun tolerant species, I. douglasiana can be grown in full sun, some shade, and decidedly damp conditions, as is to be expected of a species that grows on seacliffs from southern Oregon to central California.

Big, evergreen and tough, it confers this vigor to its progeny. Flower color varies from white to pink to yellow to blue to purple. It has multiple flowers per flowering stem, and flowers are above the foliage.

It is a member of the Klamath, Marin and Santa Cruz hybrid complexes, with the largest latitudinal range of any PCI species.

Some of the earliest natural hybrids in gardens came from I. douglasiana and I. innominata. A notable natural hybrid population formerly grew on the hillsides near Gold Beach, Oregon. This hybrid complex was known for distinctive gold, brown, apricot, orange, pink, warm purples, and other intermediate color forms. So many plants were dug up and moved that today few traces remain of this population.

Fernald’s Iris, Iris fernaldii

One of the species of the Marin and Santa Cruz hybrid complexes, I. fernaldii prefers light shade in mixed evergreen forests rather than open meadows or deep shade, and flowers a bit later than I. macrosiphon.

Flowers are a distinctive creamy yellow. Leaves are an unusual gray-green, often glaucous, and dry to a distinctive gray green; leave bases are usually brilliantly colored.

Sierra Iris, Iris hartwegii

Sierra iris grows in Yellow Pine forests of the Sierra Nevada, at mid elevations, sunny or part shade sites; generally lives above 2000 ft in the north past of its range, and at 5-6000 ft in the south, and is always higher in elevation than are I. macrosiphon and I. munzii.

The most southerly variety, Iris hartwegii var. australis, grows in several high elevation populations in southern California and is heat tolerant. It is also cold tolerant.

I. hartwegii is deciduous with distinctive pale green foliage, sometimes glaucous. It spends winters under snow and summers baking dry. It has an open, rangy growth habit rather than growing in compact clumps. It is used to confer winter hardiness and summer heat resistance.

Golden Iris, Iris innominata

This species grows on sunny to slightly shaded hillsides, well drained slightly acidic soils, rich in humus or on scree, and is often associated with Rhododendron macrocarpon, Rh. occidentale, and Xerophyllum tenax. I. innominata grows on serpentine soils and hybridizes readily with other PCI species growing on both non-serpentine and serpentine soils. It is a member of the Klamath hybrid complex.

It tolerates both winter snow cover and long warm dry summers, and is one of the hardiest species. Flowers range from intensely yellow gold to cream, to white, often well-veined in red. It is compact in habit with dark green fine foliage and red leaf bases. It is a very attractive species in the garden.

One of the first PCI grown in England a century ago was Iris “Aureonymphe” or Golden Nymph, an I. innominata selection.

Bowl-tube Iris, Iris macrosiphon

This species has a wide geographic range in central and northern California. Several iris species were described from populations with distinctive flower colors and geographic ranges and later combined into I. macrosiphon.

The present species has a wide range of flower colors, including: deep golden-yellow, cream, pale lavender, and deep blue purple. Falls are usually distinctly veined, sometimes with a conspicuous white center (signal). It is also a source of heat resistance.

Generally, it prefers open grassy meadows among oaks and other trees, and flowers early. It is a member of the Marin and Santa Cruz hybrid complexes. In habit it tends to be short, often quite inconspicuous in grasslands among taller flowering grasses and other wildflowers.

Tulare Iris, Iris munzii

The tallest of the PCIs, flower stems are up to 2.25 ft (70 cm) tall. It lives naturally in Tulare Co, California, with a wide elevation range from foothills into the Sierras, where it winters under snow in Sequoia National Park. It is hardy to at least 15 F.

Its violet, lavender, and blue flower colors have been used by hybridizers for decades to intensify blues or give a blue or turquoise shading to falls. It is also thought to confer heat resistance. Tulare iris has a stoloniferous growth habit, and a tendency to crawl around plant beds instead of staying in neat clumps.

Purdy’s Iris, Iris purdyi

This species has a small geographic distribution in northern California, where it grows on shady hillsides; some populations have more than 100 inches of rain per year.

Plants have dark green leaves with very red leaf bases; floral bracts (the leaf-like structures beneath the flowers, also called spathes) are inflated and red to reddish. Pale creamy yellow flowers are conspicuously veined with brownish purple, or pale cream or whitish with light lavender wash on falls.

Tough-leaf Iris, Iris tenax

The most northerly species, Iris tenax is often deciduous and possibly the hardiest, to zone 5. Plants are compact and grow in tight clumps, with light green foliage, leaves grow longer than flower stems, which have one to two flowers per stalk. It is a source of cold and moisture resistance. High elevation populations in the south Cascades of Washington spend winter months under snow.

Iris tenax tolerates both shade and sun, and flowers best in either full or part sun. It prefers well-drained soils, and can survive under snow and high rainfall.

It has the widest range of flower colors, from white to dark purple. There are two distinctive subspecies, including gormanii (yellow), and klamathensis (pale yellow). It is a member of the Klamath hybrid complex, interbreeding along the southern end of its range, which intersects with other PCI in the Klamath Mountain area at the north end of their ranges. The species that tenax most commonly hybridizes with in nature are I. chrysophyla, I. douglasiana and I. innominata.

Long-tube Iris, Iris tenuissima

From northern California and southern Oregon, this iris prefers shady evergreen forests, and tolerates serpentine soils.

It has lightly colored flowers, usually pale cream with very distinct veining of lavender, reddish-brown or brown. Flower parts are often distinctly and attractively crisped. It is a member of the Klamath hybrid complex.

Thompson’s Iris, Iris thompsonii

A deep purple, blue to red-violet, to lavender-flowered species in far northern California and southern Oregon, it is similar to I. innominata in habit, with attractive dark green foliage in tight clumps, and is found on non-serpentine soils in open locations.

Some researchers have lumped this species into I. innominata, or considered it a hybrid between I. douglasiana and I. innominata, but recent work on secondary plant compounds and flower structure has shown it to have both unique compounds and distinctive flower characteristics beyond petal color. In the wild, natural hybrids among these three species are common. It is a member of the Klamath hybrid complex.

The blue, blue-violet and purple flower colors are attractive for breeding, along with the dark green foliage and compact habit of growth.


For more information, see species description on this website.

The Almanacs have numerous articles on each species; see the Index for a list of articles under each species.

SPCNI reprints by Victor Cohen and Dr. Lee Lenz describe species, ecology and natural habitats in detail. These are available for sale by SPCNI, see our sales area.

Photos of species are on our Photo CD, which also includes photos of registered hybrids. See our sales area for these CDs. Photos of species are also posted on the AIS Iris Encyclopedia, in the Iris species section, by species name.