The Dry Garden: The Pacific Coast iris, a native beauty to plant in spring
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One of the most common questions during California’s wildflower season is: “Is it too late to plant?” If you’re working from seed, yes. The lupines, clarkia, poppies and sunflowers coming into bloom now germinated last fall. It is only by the capturing of residual autumn warmth and early winter rain that they put down roots needed for a vigorous spring bloom.
However, the window to plant spring wildflowers does remain open in April for our native Pacific Coast irises. This window is kept jammed open partly by the nursery trade, which often doesn’t release the plants until March -- not ideal, but possible because irises are perennials. Although they do produce seeds, they grow from rhizomes, or tubers, that produce annual sets of roots.
If we want newly bought irises to go in the ground this year, we need to jump -- fast. Unless the weather changes, it’s still cool enough. Moreover, spring shopping affords a benefit rare among natives: the chance to see at least some of the young irises in flower on store shelves.
Iris flowers come in a mind-blowing array of colors and patterns. Their variability is so legend that the name of the plant means “rainbow.” Our native Pacific Coast irises include 11 species that produce flowers in shades of white, yellow, pink, lavender, even USC-worthy cardinal and gold.
Most of the Pacific Coast irises, or Pacificas, sold in Southern California are from a single species, Iris douglasiana, pictured above planted with coral bells at Rancho Santa Ana Botanic Garden in Claremont. According to Rancho horticulturist Bart O’Brien, these Douglas irises are the most durable of the baker’s dozen of natives.
Yet even among Douglases, expect surprises. Flower colors range from the albino selection Canyon Snow, developed by the Santa Barbara Botanic Garden, to the purple-blue flowers that, when planted in mass, make Rancho Santa Ana so dreamy this time of year.
To learn about the foliage and flower distinctions behind each species classification, there is no better source than the Society for Pacific Coast Native Iris. Comprehensive breeding among species in the wild and in gardens make typing irises expert territory. You’ll know a true buff when he or she wonders aloud if the delicate Del Norte County iris might be not be responsible for the telltale luminosity of the yellow in one flower, or if the lineage of Munz’s iris, left, lies partly in the true blue of another.
My own passion for Pacific Coast irises verges on childish amazement. No other plant I know can produce a flower whose veining and hue cause me to wonder if its cousin might somehow be a tiger. In years of planting Pacificas from Matilija Nursery in Moorpark, I’ve never attempted to coordinate colors. Evolution has covered this for me. When the flowers emerge each spring, they meld together as seamlessly as the blushing hues of a rain-washed dawn sky.
Clashes can emerge when mixing native Pacificas with the exotic bearded irises sold in garden centers. I have done this, and the imports can do just fine on a water diet, like the natives. But keep in mind that bearded irises are often bigger. Leaves in established plants can seem almost sword-sized. Their flowers can seem huge, outlandishly frilly or too brightly colored. Next to a Pacific Coast iris, a bearded iris can look like Liberace parading through a Ralph Lauren catalog.
Pacificas tend to be small and elegant. Their slender leaves look more like clumping grass. To my mind, this understated quality makes the native irises a far better fit for a woodland or meadow garden.
The differences continue below ground. The rhizomes of the bearded irises are far tougher than those of our natives. The toughest beards can be yanked from the ground, trimmed of foliage, put in a padded envelope, sent to a faraway aunt, left on the doorstep for a week and still end up upstaging everything else in her garden.
By contrast, Pacificas might not forgive you if their small white roots were left exposed to heat or air for more than a few minutes. It helps to know that rhizomes only produce small, tender white roots in late fall, usually mid-November to early December usually. Like the rest of our native wildflowers, the root system and foliage will then grow during the cool, wet months of December, January and February before exuberant flowers appear in spring.
If you buy and plant a Pacific Coast iris now, keep in mind that it’s only spring for you. For the plant, this is the third of its four-season act.
Give them a year or two of morning sun and dappled afternoon shade, and the small fans that began in 1-gallon nursery pots should become vigorous clumps producing lots of flowers. When planting, space seedlings or clones no closer than 18 inches apart. Take care not to bury the crown, and position them so the soil line falls where the rhizome and leaves meet.
The textbooks say that Pacificas appreciate slightly acid soil. Experience tells me that they can endure neutral clay. I like to face the fans in the same direction -- a fussy instinct -- but once they fill out, positioning won’t matter. In spring, plant them in a place with dappled light. Labels for bearded irises usually recommend full sun. The label probably was printed somewhere cold. Here in California, afford them some shade. O’Brien suggests near deciduous trees, so irises have full winter sun and summer screening.
Water them well enough for the first couple of weeks so that those tender roots don’t dry out. Stop watering once flowers furl up and seeds begin to form. O’Brien recommends cutting the pods off young plants to spare their energy reserves during the hot summer months.
By June, even newly planted Pacific Coast irises will be dormant, requiring only occasional watering. This regimen should follow an overall strategy for watering a native garden. But keep in mind: The plant is dormant. Its leaves only look like grass. Watering it like lawn will kill it. If you want to thin old foliage, trim instead of pull. I find the red and brown striping of old leaves to be attractive. That said, if all the foliage is brown, the plant isn’t dormant, it’s dead.
Horticulturist Lili Singer of the Theodore Payne Foundation for Wildflowers and Native Plants says to expect 5% mortality when planting native irises. During spring, that rate may be higher. But if you’ve seen a California native iris in flower in spring, odds are that you’ll keep trying.
-- Emily Green
Photos, from top:
A Pacific Coast iris grows among blue-eyed grass. Credit: Rancho Santa Ana Botanic Garden
Three Pacific Coast irises show just how varied the colors can be. Credit: Emily Green
Douglas irises, the most common species, grow alongside pink coral bells at Rancho Santa Ana. Credit: Bart O'Brien
Munz’s iris carries a blue-purple hue. Credit: Bart O'Brien
A Pacific Coast iris in a softer shade of purple and yellow. Credit: Emily Green