The Beardless IrIses of Series Californicae, often popularly called Pacificas or Pacific Coast Irises (PCIs), are known for widely diverse flowers, being extravagant as to flower shapes, colors and patterning. Some of them are too large for the rock garden but some are very much in scale with what many rock gardeners look for.
Species in the series (part of the Beardless Iris section Limniris) hybridize easily with each other. Modern hybridizers may work with clones that are forty to fifty generations removed from wild species, and the range of modern flowers is simply spectacular. New patterns appear every year. Plants often flower in the second year, so determined hybridizers can quickly select desired forms.
There’s a downside to the floral glory of Pacific Coast Irises, which is “impatience” with conditions they do
not like (read “die”). Native to the West Coast of North America, the species (there are twelve of them) grow naturally from the San Bernardino Mountains in southern California to southwest Washington in the Cascade Range, and they and the hybrids are commonly grown from southern California to southern British Columbia, Canada, west of the Cascades. Outside this region, they are often seen as too fussy, too delicate, or too difficult to bother with, no matter how wonderful the flowers. This has not prevented gardeners in other areas from continuing to try to grow them, and this article focuses on ways to succeed (or attempt to succeed) with them outside the home range.
Members of the Society for Pacific Coast Native Iris (SPCNI) grow them in Europe, British Isles, Australia and New Zealand, and the society formerly had members in Mexico and South Africa who also grew them. By comparing climates, gardeners in temperate parts of Chile should be able to grow Pacific Coast Irises, as should gardeners who live a few thousand feet above sea level in otherwise too-hot areas, including east to southeastern U.S., the Iberian Peninsula, Italy, Greece, and other countries around the Mediterranean Sea. Lowland China may be too hot, but higher elevations may work, likewise in Japan, and even Hawaii, up a few thousand feet from sea level.
PREFERRED GROWING CONDITIONS
Pacific Coast Irises are not wetland plants. They do not like wetland soils, standing water in summer or winter, daily watering, or being submerged in water.
Pacific Coast Irises prefer acidic soil with excellent drainage, some moisture from fall to spring, organic amendments including compost, biochar (biologically activated charcoal) and mulch, cool roots, good
air circulation, and full sun to part shade to full shade, depending on summer heat. The rule on shade and heat is that the hotter the summer is, the deeper the shade should be. They flower from late winter to late spring or early summer, depending on latitude and temperatures, and are green but dormant, their roots inactive, from summer into early fall. Where winters are cool, roots are inactive again, whereas in moderate winter areas with ample moisture, such as the maritime Pacific Northwest and British Isles, established plants may have active root growth almost all year.
TRANSPLANTING
Pacific Coast Irises can be lifted, divided, and transplanted safely only when in active root growth. This is easy to check: Scrape away the soil at the base of the plant and look for white roots. If the roots are brown or dark, they are dormant. If they are white and one to four inches long, the plant is in active growth, and it can be moved. If roots are shorter, place the plant in water in a well-lit airy spot until the roots have grown to
an inch long.
Plants native to the West Coast are usually best transplanted in fall. By transplanting them in the fall, Pacific Coast Irises have the cool damp months of winter to establish. Photosynthesis by existing leaves supplies energy, with extensive root growth underground. The benefit of fall planting is equivalent to two years of growth after spring planting.
You may find that Pacific Coast Irises are available in your area only in the spring, so that you have no other option but to plant in that season. Remember to check the roots to see if they are alive (white). If they are white and in active growth, then go ahead. If you commit to this, however, you are also committing to regular watering that summer, especially in a warm summer climate.
In a hot dry climate, it is better to prepare the soil in spring and plant then, than to wait out a long hot summer with them in pots. Plants can be held over the summer in cool shade, though I have taken them gently out of their pots in late spring to early summer, and planted them successfully. I have also killed Pacific Coast Irises by holding them in pots in locations that were too hot by midsummer, and I live in a cool summer area, zone 8 on the south coast of Washington in the Pacific Northwest.
For young plants, and newly transplanted plants, regular watering in dry summers is important for the first couple of years with watering needed each week initially, and then biweekly to monthly. for most nurseries and gardens along the West Coast, this means that fall or spring are the only times when Pacific Coast Irises can be shipped. Nursery by nursery, each business knows what works for its plants. Sometimes this is in spring; most often it is in fall. Seedlings and young plants are tougher than older plants, so during the first year or two they can be kept in pots and moved with good odds for survival. Older plants are more floriferous, but easily die for a number of reasons, which is why mature flowering three- to five-year-old plants are rarely for sale. One grower in southern California grows them in large pots with very good drainage, using a mix that is about 45% perlite. His plants can be transplanted in spring or fall and usually thrive. He starts new divisions out in 85% perlite in small rose pots, and adds more compost to the mix as plants go up in pot sizes.
They dislike having hot roots. If their roots get too hot during active growth, they check out quickly. This precludes them being shipped out of country as bare-root starts, because they cannot tolerate the indoor wait
of days to several weeks or more for inspection at customs offices. International shipping that involves custom inspections must be of seeds, not plants. Seeds are tough, can be kept for several years, and germinate fairly easily. See the SPCNI website <www.pacificcoastiris.org> for more information on starting seeds, transplanting, and gardening.
EXTENDING INTO OTHER CLIMATES AND ZONES
The astute reader will note that the home range of Pacific Coast Irises encompasses horticultural zones 10 to 7, with small dips into zones 11 and 6 and even 5. But what about the rest of the world? Solid zone 5 and colder zones are a challenge, as are warmer zone 10 and 11 areas. This brings us to the heart of this article: Pacific coast irises thrive in the right spots, and die quickly when too cold, too hot, too humid or too dry. So how are gardeners in other zones to succeed? let’s deconstruct the growing conditions and climates that they prefer to see how this range can be extended.
COLD WINTERS
Winters in zones 6, 5, and colder are usually fatal for most of these irises. While some species (Iris chrysophylla, I. innominata, I. tenax, I. thompsonii) grow at high elevations in the cascade, Siskiyou and coast ranges where they often spend winters under snow, dry cold conditions must be avoided. loose open mulches, such as pine needles, and adding extra snow over beds helps to insulate plants from dry winter cold. Below zone 5 plants cannot survive, and containers that can be moved may be the only way to keep plants alive.
A gardener in Boise, idaho, with dry cold winter conditions, piles extra pine needles on her Pacific Coast Iris beds and then adds snow whenever it falls, to provide added insulation and keep the plants dormant and well protected during the coldest weather. the coldest weather often comes without snow cover, so she plans on starting new plants from seed if no snow falls that winter. Boise also has long, dry hot summers; she waters in summer by checking the weather in Seattle, Washington. if it’s raining in Seattle, then she waters. if not, then she waits. She also plants her irises in well-shaded beds. Iris douglasiana and selections from this species have generally done well for her from year to year, with the occasional complete replacement of plants following severe winters.
The Denver Botanic Gardens, Denver, Colorado, has grown Pacific coast irises for many years. the plants are shaded by large rocks and trees, and are in well-drained soils, to get the cool root-runs they prefer. this garden is at 5,400 feet elevation on the east side of the rocky mountains. denver is in zone 5b, with dry warm summers and cold, snowy winters.
Growing conditions that can help them survive cold include enhanced drainage, with gritty, low-fertility soil, and placing plants on a slope so that water drains away. in winter snow areas, don’t cut the leaves back in fall. leave them on until early spring to help insulate the plants during winter. Excellent drainage is especially important in summer irrigation gardens. they do not like much water at all in summer, so it is important that their roots have every chance to shed excess water.
Plants to try in colder winter areas include Iris douglasiana and clones selected of this species. this is the toughest species in the series Californicae and ‘Canyon Snow’ is a selected form of it. ‘Pacific Rim’,
a complex hybrid, is another tough plant that usually does well in gardens are both selections that have proven to be durable compared to other species and hybrids.
If you also have humid summers, then good air flow is very important. Don’t bury Pacific Coast Irises among shrubs in deep shade with poor air circulation.
DRY, HOT SUMMERS
Periods of very hot weather occur on the southern West coast of the u.S. in zones 9–11. the basic change made by many gardeners in southern California is to plant Pacific Coast Irises in deeper shade with good air circulation.
Shade, with sunlight only for a short period in the morning, is a good solution for areas where daytime temperatures in the hottest period of the summer are usually in the 80Fs to 90Fs. as with colder climates, well-drained acidic soil, additional organic materials and deep loose mulches help insulate the roots to keep them cool. Where hotter still, full shade and weekly watering may keep the irises alive until they establish well, which may take 2–3 years. thereafter, they should thrive with watering every two weeks during the dry season.
Containers for Pacific Coast Irises in hot climates must be insulated to keep roots cool. Styrofoam fish boxes are a good solution, especially if larger boxes are used so that plants can grow for several years without being disturbed. a gardener on San Francisco Bay uses half barrels, where the irises grow undisturbed for several years. they get summer water every few weeks, and the barrels plus soil have enough mass that plants do not overheat. he places the barrels so that they get sunlight for the morning, and are in shade through the hottest times of day.
Minerals in the water may build up to intolerable levels in warm summer regions. they prefer acidic soil, after all, not caliche. as wells draw down, mineral content can increase dramatically. a grower in southern California uses pHacid, an irrigation and soil water acidifier, as a soil spray and watering amendment, to help move minerals through the potting mix, which improves plant survival where carbonates, sodium and minerals are a problem.
A member of SPCNI lived in the Central Valley, California, where late summer temperatures regularly went above 100 F, and grew her plants under citrus trees in full shade. the citrus trees were watered every few weeks by flooding, and the irises thrived for decades with this treatment.
HUMID, HOT SUMMERS
The one climate combination that Pacific Coast Irises cannot stand is high heat and high humidity. in this summer combination, try rain guards in summer to keep rain off the plants. the rain guard can provide shade too. Plant in well-drained soils in deep shade with good air circulation (a difficult combination sometimes), with at most a little early morning sun. avoid hot spots in the garden, aim for deeper shade at the hottest time of day. or move up into the mountains a few thousand feet, where conditions are cooler and less humid, and try again.
SPCNI had members in mexico city, mexico and in the drakensburg mountains of South africa who both had success for many years. Elevation helped, both lived above 5,000 feet; their plants had both shade and summer irrigation. if you garden in a humid, hot summer area, but at higher elevation, give them a try. your microclimate might be moderate enough that they can survive.
THE BACKUP PLAN
Save seeds every time your plants sets them. no matter how successful you may be with Pacific Coast Irises one year, save seeds for the inevitable day when all your plants die from unforeseen weather events. Seeds can be stored in a refrigerator for several years (clean and dry, in plastic bags, for up to 5–7 years), so this is simple protection. Some gardeners in hotter summer and colder winter climates plan on regrowing their own plants from seeds every three or four years. This way, they get a couple of years of flowers and seeds from each plant, and keep some plants flowering in the garden year after year. This is treating them like short-lived perennials, yes, and in some climates, this is the best that can be achieved. After a few generations in your garden, by repeating the cycle again and again, you may see improved tolerance for local conditions. Remember that seeds are the result of sexual reproduction, so seedlings will not be exact genetic replicas of their parent plants.
A SELECTION OF PACIFIC COAST IRIS TO TRY
not all Pacific coast iries can tolerate the same range of conditions, cold to hot, moist to dry. Some species and hybrids are well known to be tougher than others. Modern hybrids have been bred to be compact plants with flowers held above the foliage. But these are not the toughest in the garden, even on the West coast. for sturdy plants in climatically difficult areas, start with selections known to be durable, and if you succeed with these, then get a few of the more brilliantly colored hybrids, and see how they do.
Iris douglasiana is the toughest species among the Californicae irises. Growing from southern oregon to southern california, Douglas iris lives along the coast, where it can take wind, salt, drought, heavy
rain in winter, and snowfall. foliage is evergreen; flower color varies widely, and flowers are on multi-bud stalks and held upright. There are vigorous strains available, often with foliage to 30 inches (75 cm) tall. The flowers are species-like, with fairly narrow petals and limited color ranges, but your first goal is to get any Pacific coast iris to thrive in your garden; after that you can try showier modern hybrids. Iris douglasiana is a potential first choice for hotter and colder sites, especially if growing in containers, and for areas with summer humidity.
‘Canyon Snow’ is a white- flowered selection of Iris douglasiana made at Santa Barbara Botanic Garden several decades ago. it emerged quickly as a tough plant for southern californian gardens, and it remains in cultivation today. ‘Canyon Snow’ is a good first choice for both cold winter and warm summer gardens.
‘Pacific Rim’ is remarkably tough once it is established, with a medium blue plicate pattern on white flowers. It tends to be a dominant parent in breeding.
‘Clarice Richards’ is a hybrid developed by Richard Richards in southern california. It performs well in hot locations, and should be considered by anyone in these climates. Also try it in colder climates, as it does well in the Pacific northwest.
Others to try in hot areas include: ‘San Ardo’, ‘Untitled’, ‘Now Showing’, ‘Wilder Than ever’ and ‘Garden Delight’.
Iris bracteata, I. innominata and I. tenax grow at higher elevations in the Pacific northwest, and should be tried in colder areas. These species require excellent drainage, unlike I. douglasiana, which is more tolerant of heavy soils. in the wild they may spend months under snow cover. At the very north end of its range, I. tenax grows at elevations of around 3,000 feet in the cascades in southern Washington. This population is under snow most winters. for colder climates, this species is definitely worth trying, but note that it, like the other species mentioned here, need excellent drainage.
Although seeds of Iris hartwegii are not often available, seeds from the southern california plants, which live at high elevation, are worth trying in colder zones as these plants may spend winter under snow (in years when there is snowfall in southern california). it flowers better with winter to spring moisture and hangs on in prolonged drought, which unfortunately has been underway for several years in its native habitat. it grows in my own garden on the south coast of Washington, in sand, and even flowers every few years.
RECENT DEVELOPMENTS
Pacific coast irises have been selected for flower form, color and patterning for more than fifty generations. Upright flower stalks and sturdy plants have also been selected. The changes in flower form during these generations of selection have been startling. Petals are wider, ruffled, more open, or flatter. color ranges from very dark purples and near reds to whites are now common. Signals have developed halos of other colors. veining can be striking, with almost no signal, and veins throughout the falls. edging of falls may be narrow to wide, of contrasting color. Standards and style arms may be the same color, or contrasting, held upright or at a low angle, with ruffles, or edging.
However, there has also been trend towards smaller plants, which has led to a reduction in plant vigor. Retention of vigor may be important for gardeners outside the West coast so, it may be necessary to go back to larger older hybrids, and to species, in less than optimal climates.
A few hybridizers have worked on wide crosses, typically between Californicae and Sibiricae series. for a recent summary of wide crosses see the Spring 2014 issue of Pacific Iris, available from SPcni. The goal of wide crosses is to produce colorful plants that can withstand hotter, damper and colder climates. To date, while the colorfulness goal has definitely been achieved with cal-Sibes and other wide crosses, the other goals have not, generally because the 40-chromosome Siberian irises that cross most easily with Pacific coast irises are not from colder climates.
These crosses are sterile. To get around the sterility, some hybridizers induce polyploidy by using chemicals (colchicine, Surflan) on germinating seeds, with some success. Dr. Tomas Tamberg, Germany, has done this for several decades. The field remains open for new hybridizers to take up the task of producing hardier plants by making wide crosses with genetically compatible irises of other sections.
SOURCES
SEEd SOURCES:
To start Pacific Coast Irises from seed, see the SPCNI website, which has several pages on cultivation. All of these seed exchanges are for members only, and ship seeds outside the United States.
SPCNI Seed Exchange <www.pacificcoastiris.org>
This seed list is open in late fall each year, and usually closes around the end of the year. Past years’ offerings are listed for reference. This list has the widest range of species and hybrid PCI seeds, and only offers seeds of Californicae irises.
SIGNA (Species Iris Group of North America) Seed Exchange <www.signa.org> This seed list is open in winter each year, and seeds remain available for several months. Past years’ offerings are listed for reference. This list offers seeds of Iridaceae species from all over the world.
NARGS Seed Exchange <www.nargs.org>
This seed list is open during winter each year, and includes a few PCI selections in most years.
PlANT SOURCES
There is an extensive list of nurseries on the SPCNI website at <www.pacificcoastiris.org/gardeniris_nurseries.html>
PHOTO CREdITS
Photos by the author except:
Lewis and Adele lawyer (I. innomiata p.327, I. ‘Clarice Richards’)
Ferrell (Iris douglasiana p.327)
Richard C. Richards (Iris ‘Canyon Snow’)
Ken Walker (Iris tenax p.327, I. ‘Pacific Rim’, I. ‘San Ardo’, I. ‘Now Showing’, I. ‘ Wilder Than Ever’)
Garry Knipe (Iris ‘Finger Pointing’)
The Pacific Coast Iris Species
The genus Iris has 200+ species and is subdivided into sections and some of those are subdivided into series. There are twelve species and several subspecies in series Californicae.
Iris bracteata – 20-30 cm – white to pale yellow – Klamath & Siskiyou Mountains.
Iris chrysophylla – 20 cm – white or cream – Cascades in Oregon, Klamath & Siskiyou Mountains.
Iris douglasiana – 70 cm plus – white, yellow, lavender, to purple - always coastal, California to southern Oregon.
Iris fernaldii – 20-45 cm – typically pale yellow or cream - limited in coastal central California.
Iris hartwegii - 10-30 cm - typically pale yellow or cream – Sierra Nevada valleys and mountains of southern California.
Iris innominata – 20-25 cm – rich yellow – Siskiyou Mountains, Oregon. iris macrosiphon – 15-25 cm – cream to yellow, lavender, or purple -
widespread in northern California.
Iris munzii – 75 cm – lavender to purple – small area in Sierra Nevada foothills.
Iris purdyi – 30 cm – cream – northern Coastal Range, California.
Iris tenax – 30 cm – lavender to purple, rose, blue, yellow, pink, white - Cascades in southern Washington, Oregon Coast Range and Cascades, and also small population in Californian Klamath range.
Iris tenuissima – to 30 cm – cream – northern California.
Iris thompsonii – typically lavender to purple – Siskiyou Mountains in
Oregon and California, Klamath Range in extreme northern California.
Most modern Pacific Coast Iris hybrids are derived from multiple-species garden crosses, starting with species growing around the San Francisco Bay area before WWII, and Iris innominata.
