Phenology of Pacifica Iris during Climate Shifts

Kathleen Sayce

Phenology, or the study of what condition plants are in (onset of growth, vegetative, pre-flowering, flowering, seed set, dormancy) at what date during the year, is fascinating to track during climate shifts. No, I’m not talking about climate change, but about regular weather cycles on the West Coast of North America. 

Iris tenax, wild collected seed from sea cliffs by Manzanita, Oregon, was flowering in June, and now has numerous pods. 

There are several regular cycles that last six months to twenty months or so: 

First, the familiar one–– the annual season, which cycles every year through winter, spring, summer, fall. 

Second, El Niño-Southern Oscillation Events, ENSOs. In the popular press, these are called El Niño, which bring warmer than usual weather to the Pacific Northwest, and range from dry to wet weather in winter depending on ENSO intensity and latitude on the West Coast. California often gets much wetter winters during ENSO events. 

ENSOs alternate with two other weather states over the Pacific Ocean. The other two are La Niña events and ‘neutral conditions’. La Niña events bring colder than normal weather to the West Coast, and neutral conditions in the Pacific are just that, not strongly warmer or colder. These three states of weather over the Pacific Ocean impact weather around the world. The National Weather Service posts intermediate to long term forecasts which can help us see what is coming over the next few seasons. 

Third, there is also a longer weather cycle, the Pacific Decadal Oscillation, which typically lasts twenty to twenty one years, warm and dry or cold and wet. In the warm and dry state, the Pacific Northwest has less rain, salmon populations fall as fewer fish reach streams to breed, and ocean conditions are poor for their growth and survival. Snowpacks are reduced in the mountains. At the same time, Alaska and northern British Columbia get the opposite, more rain and cold weather. The flip side is cold and wet in the Pacific Northwest, and warmer and drier to the north. 

I. douglasiana X I. chrysophylla has sturdy spikes with multiple flowers, on a tall plant that grows in dense clumps. I'm planning to divide this one at the next garden redo. 

The Pacific Decadal Oscillation flipped to warm and dry in the Northwest last year, with a strong ENSO event on top of it. We had a long dry summer last year, bracketed by two wet winters. This year saw average snowpack form, but it melted early as the weather warmed. 

What does this mean for Pacifica Iris in northwest gardens?  Flowering begins earlier, progresses faster, and is over earlier in the summer. Pollinators are often out of step with the bloom times, so seed set can be reduced on open pollinated plants, especially for those that are early flowering. 

Grown from SPCNI seeds, this late flowering PCI has unknown parentage, but often flowers into June. Flowers are species like, small and numerous on a medium-sized plant. 

During cool springs and cool to cold weather cycles, Pacifica Iris start flowering in April, peak in May, and continue into July, some years to mid July. During warm dry weather, iris begin flowering in March, peak in April, and are done by early June. This is months later than southern California gardens, and trails northern California by at least six weeks. 

The last Pacifica Iris to flower are a sturdy handful, including two species crosses and a local species. Those lovely frilly hybrids are long past when these irises start to flower. 

Iris tenax from Saddle Mountain, Oregon, also has nice rose-purple flowers.

Iris tenax from Saddle Mountain and the sea cliffs near Manzanita, Oregon, generally starts in May and finishes in June, with rose-purple flowers. 

A cross between I. douglasiana X I. chrysophylla with tall stems and flower spikes, and small dark purple flowers [seed from SPCNI several years ago] is one of my favorite May to June flowering clumps. 

Another cross between I. tenax X I. innominata also from SPCNI, flowers in May and June, and can be stunningly floriferous in cool wet years. I have white, pink-veined, and lavender clumps of this cross. 

Dwarf I. douglasiana is still flowering in late June. Also the slowest to ripen pods, I'll be collecting seeds in September from these plants. 

The last to flower, still in bloom in July most years, is a dwarf I. douglasiana, typically less than twelve inches tall, with sturdy short stems and lavender flowers. This also came from the SPCNI seed exchange, donated by Diane Whitehead from her garden in Victoria, British Columbia. 

Today as I checked the garden [too many weeds getting ahead of me already, ugh] I saw few to no pods on the early flowering irises, but the late flowering irises had many fat buds, already ripening seeds. 

With warm dry weather in store for the next couple of decades, I think it’s time to focus on these late flowering plants for the next generation of new Pacifica Iris in my garden.