Monday, June 10, 2019

Wild Iris tenax on Seacliffs in Northwest Oregon


By Kathleen Sayce

Iris tenax grows on mountains in northwest Oregon, including Saddle Mountain, Clatsop County, Oregon. This species is usually found on south facing slopes along the main trail and in meadows with wild cucumber, native grasses, paintbrush, and other wildflowers. It also  grows on seacliffs in several locations in Clatsop County. These locations are in state parks, Ecola and Oswald West, and are as far north as I. tenax grows on the coast. 

This plant has narrow falls that are mostly lavender towards the tip with a large yellow signal and smallish white patch. 
North of Clatsop County, this species grows in the Coast Range and Willapa Hills, in the Chehalis lowlands south of Olympia and east of Montesano, WA, and in the Cascade Range. But it does not grow along the coast north of the Columbia River. 

Seacliffs are one of the harshest environments plants can endure. They must tolerate high winds, salt water, salty air, winter wet conditions, high summer temperatures, prolonged drought, and erosion. The ability of any plant to withstand this combination of chemistry, wind, moisture levels and temperatures is amazing. 

This plant had the widest falls and standards, and a deeper pink-lavender color. Both falls and standards were wider than on other plants. 
Visiting these hardy plants is one of my annual pilgrimages. Like the departing Brant geese and returning swallows, seeking out wild Iris tenax when in flower is an activity that says “Spring.” 

A few years ago, I found a population of about five plants on the seacliffs above Manzanita, Oregon. These tenacious cliff-dwellers had larger flowers, and leaves that were easily twice the size of all the other I. tenax plants in this area. Seeds and a small fragment came to my own garden, where they thrive, and from which I collect seeds regularly for the SPCNI seed exchange. 

This Iris tenax plant had moderately narrow falls, and larger lighter colored areas. Standards were lavender; style arms were much paler, almost white. 
But remember erosion? As of my last visit in 2018, the block of eroding rock and meadow that this population lives on had slumped so much it is no longer safe to even climb down to get closeup photos of the flowers. It will be gone soon, reclaimed by the Pacific Ocean.

This large clump had a tiny yellow signal with a larger white patch around it, and moderately wide falls. Flowers are darker as they open, so I was careful to compare colors among flowers at the same stage 
This week I went back to see the plants in Ecola State Park. Two trails that passed by several populations of Iris tenax are closed due to landslides on the seacliffs. One trail is left that takes in a few plants, and these were flowering. They were still flowering two weeks later when I led a native plants group out to see them. The trail winds up a south-facing, exposed and eroding cliff face, so while these plants will be here for a few more years, in geologic time their fate is already clear:  they too will enter the Pacific Ocean very soon. 

The view along the trail to the northwest, with "Terrible Tilly", former Tillamook Head lighthouse, in the middle left. Note eroding cliffs along the headland.


Diversity in flower shape and color is generally based on where plants grow relative to their larger population. Outlier populations (on the edges) tend to be less diverse, and plants within a main population tend to be more diverse. All the photos in this article were taken at this one site near Indian Beach, and you can see the diversity of shape in petals, and in range of flower colors. From this residual diversity, we may conclude that many iris plants that formerly lived along this shoreline have already fallen into the ocean. 

But, Iris tenax still lives along the seacliffs today, and is flowering. Life is good. 


The World of Irises is the official blog of The American Iris Society. Now in its 99th year, The American Iris Society exists to promote all types of irises. If you wish to comment on a post, you can do so at the end of the page and the author or the editors will reply. If you wish to learn more about The American Iris Society, follow the link.

1 comment:

  1. Amazing post with lots of informative and useful and amazing content. Well written and done!! Thanks for sharing keep posting.

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