Monday, June 2, 2014

What Rains May Come to Pacific Iris Flowers

Kathleen Sayce

Irises are at an inherent disadvantage in a spring-wet climate, because they have upturned flowers like tulips instead of down-turned flowers like many lilies. Hybridizers in dry spring areas have selected for wide, frilly flowers over the past few decades; usually these plants flower in late winter to mid spring. In spring-wet areas, these flowers are hammered by rain, damaged so badly that pollination cannot occur. 

A modern wide-petaled, frilly Pacific Iris flower on a dry day. This is an unnamed seedling, flowering for the first time this year.  
So what's an irisarian to do with wet weather during flowering?  The answer is to evaluate flowers to see which ones do well, or at least better, in intense rain. Most of us can live with moderate damage, and are happier with a colorful spring flower display that doesn't look like soaked tissue paper was tossed around the garden. 

When it rains during flowering, I take a waterproof camera into the garden and record how well each flower and its plant hold up. Flower shape is important. Stem sturdiness is important; lovely flowers that lay flat on the ground (due to weak stems) are not going to make the cut. Very important is how well the flower survives being battered by rain and wind. Enough rain, and any iris flower can be battered into oblivion, so the following is a first attempt at a weather-tolerance scale.

For this year, the following is the result of rain-on-flower observations in my garden:

Wide frilly flowers often fare badly in heavy rain; they can tolerate light rain. The petals are thin, and a few days of intense rain shreds them to fragments. 

The same unnamed Pacifica Iris seedling following an intense rainstorm. Its wide petals tend to melt in heavy rain. The damage to the falls is not a deer or slug, it's rainfall that tore off portions of the petals. 
Yellow flowers typically melt in heavy rain. Open one day, gone the next. It's quite shocking to see how poorly this color fails to hold up to a good storm. Do any yellows hold up well in rain? I grow four or five, and am going to research this in coming years. One of the yellows has weak stems, and these are battered to the ground in storms. It's toast. 

Another unnamed seedling, a lovely yellow, after a rainstorm. Note the damaged style crests and standards, and melted falls. 

White flowers vary in durability. Some do well. Others melt. Doug' flowers (Iris douglasiana selections and crosses) are at the core of many reliably sturdy hybrids. 'Canyon Snow' is very sturdy for a white flowered Pacifica Iris, and is a Doug' selection. 'Cape Sebastian' is an unregistered Doug' selection with a white flower and purple signal, and it also does well. Both have been available for several decades, and are highly recommended. 

'Canyon Snow' when dry, above, and wet, below. This Doug' selection holds up well in rain with sturdy upright stems and durable flowers. 

Older hybrids have narrower petals and less frilling, and often do surprisingly well in heavy rain. Go back about 20 years, to find these sturdy forms. 'Mission Santa Cruz' and 'Cape Ferrelo', to name two, also do well in intense rain. 

'Harry's Rootbeer' holds up in rain. This hybrid is a 'Mission Santa Cruz' progeny, bred for southern California, which also does well in the Pacific Northwest. 

Species and species crosses often also do well. This includes Iris tenax, I. tenax x I. innominata, I. chrysophylla  x I. douglasiana, and others. Flower petals are sturdy and narrow compared to modern hybrids. Flowers are held upright on strong stems, which rarely flop on the ground in heavy rain. Only I. innominata tends to melt and flop. 

Iris tenax from Lewis County, Washington, does well in rain, as do many Pacifica species. 

I. tenax is usually upright and sturdy, with flowers holding well in all but the most intense rains. No surprise, this species is native to the Pacific Northwest, and flowers latest in my garden. 

From observations made this spring, I know that some yellow flowers melt in heavy rain. I plan to look for and breed for sturdier yellows, and use rain screens to protect plants now. 

For those large frilly flowers, use rain screens. If my climate is consistently wet in mid spring when these ruffled beauties flower, then I have to be ready to lose them. They may be toast as well. 

Older hybrids, in a wide range of colors, do well. Rejoice! Use rain screens over the plants I want seeds from, and enjoy the flowers, rain or shine. The ideal form has strong petals and sturdy upright flower stems. 

As for species, they flower very well, so long as I keep away from yellows. Too bad for me that the yellows are my favorite color. I'm just going to have to get over it. I would like to know if readers have similar observations in wet spring areas. Are there particular colors that rain damages more in your garden? Or flower forms that do not hold up well to your weather?


  1. Which types/varieties would do well in the Northern NJ area? And where might corms be purchased?

    1. New Jersey is a bit outside the comfort zone for Pacifca Iris, due to humid hot summers. To try them, plan on a very well drained soil, and covers to provide summer protection from rain to keep the roots and plants somewhat drier. They also need to be protected from winter cold. Snow cover is great, but cold without snow cover will kill them.
      Pacific Irises do not produce corms, they have fine rhizomes, and should be planted in spring or fall when roots are growing.
      A recent article in Pacific Horticulture, Winter 2014, includes growing tips and sources.
      Sturdy Pacifica Iris include Canyon Snow, Mission Santa Cruz, and Pacific Rim, to name a few. Check the article for sources (you may have to join on line to read the full content).
      I will have an article in the Rock Garden Quarterly later this year, on growing Pacificas outside their native range, which may give you many good tips.

  2. I hate when it rains when the iris are starting to bloom, especially for Japanese Iris. Your blooms are still very beautiful!

    check out my recent post on my Japanese iris blooming,

  3. I tried Japanese iris for several years, and found that the rain was too hard on the flowers. Also, slugs loved the flowers! Between rain and slugs, I rarely could enjoy their flowers, so out they came. If you can grow them well, I envy your growing conditions. If I had large covers, and ducks to keep the slugs down, or less rain in spring, they might be OK in my garden.


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