For the Love of Iris

Articles, Tips and Notes from Schreiner's Iris Gardens

Early or late, how long will we wait, for beloved Iris to bloom?


Digging the dusty acres; passing rebloomers on the way back to the farm...

Digging the dusty acres; passing rebloomers on the way back to the farm…

“The Iris are coming on earlier than usual this year!” Sound familiar? Or, “This is the latest bloom season we’ve seen in years!”  As we dig the remaining acres of Iris for the season, we are simultaneously planting for next year’s bloom. We ask ourselves each fall, “Will next spring be early or late?” ….Late or early, is global “climate change” to blame for the flip-flopping perennial habits of our beloved Iris?

A recent inquiry from a customer in the Bay Area regarding the unusually early onset of her Iris blooms prompted us to ponder the question further. We consulted with our good friend, and fellow Iris enthusiast, Dr. Benjamin Herman, Climatologist with the Department of Atmospheric Sciences and the Institute of Atmospheric Physics at the University of Arizona, Tucson.

On the question of how much effect “climate change” can have on the bloom time for Iris, Ben Herman writes, “While I have never tried to relate bloom time to climate change, I think we have to define what we really mean by climate change. The warming that has been taking place over the past 30- 40 years that is usually referred to as climate change has been of the order of, at best, a few tenths of a degree per 10 years, or about 1.5 degrees per century. Natural changes from year to year can be considerably more than this, but it will vary from year to year. Over a ten-year period, I think it would be difficult to see any significant change in the bloom time for Iris due to “climate change.” Year to year natural changes however, could and do cause noticeable changes, but in general, it wouldn’t be always in the same direction. By that I mean one year it could be late, another year it could be early, etc. I think all growers that have been at [Iris growing] for many years have experienced this.

Warm spring brings early buds

Warm spring brings early buds

There could be other causes also for changes in bloom time. Rainfall amounts could have an effect as could cloud cover. I would guess that more than normal cloud cover might delay bloom time, while the opposite might move it forward. However, temperature variations are probably the largest control over bloom time. Those of us in more southerly regions of the U.S. generally have bloom times from mid- to late April, while more northerly regions are generally from late May into early to mid-June, the latter dates applying to the colder northerly regions. These dates, everywhere, can vary due mostly to temperature changes, but I do not believe that the changes due to what we refer to as “climate change” can have a noticeable effect over a ten year period.”

Thank you to Benjamin M. Herman, PhD, Professor, Atmospheric Sciences (Institute of the Environment, University of Arizona) for his contribution to this month’s post!


The U.S. Department of Agriculture (USDA) issued an updated Plant Hardiness Zone Map in 2012. This map shows the slight changes in zones compared to the previous map issued in 1990. Wondering what your USDA Zone is? Visit the USDA website for more information.

As we plant our Iris around the gardens this month, we trust in the cycles of nature to deliver us our much-anticipated Iris bloom season next May. Have you noticed changes in the bloom habits of the Iris in your garden or your region? We’d love to hear about your observations.

Author: Schreiner's Iris Gardens

Dedicated to growing and selling the finest Iris in the world.

8 thoughts on “Early or late, how long will we wait, for beloved Iris to bloom?

  1. We have a correction to make to the original version of this post published on 09-09-13: Ben Herman (spelled with one “n”, not two), is with the Department of Atmospheric Sciences and the Institute of Atmospheric Physics at the University of Arizona — not the Institute of the Environment, as stated in the original post. We apologize for any confusion this error may have caused.


  2. Our seasons here in SW NYS are perfectly normal, right on schedule, just that the winters have mostly not been quite as deeply cold, and I am sorry I paid money for your full catalog, which arrived the day AFTER the date you are willing to ship to this area, therefore your $5 catalog is no good. It is still planting weather here.


  3. Appreciate a science guy who speaks the truth to environmentalists gone over the edge. After 2012 normal weather, 2013 spring was two weeks early, summer two weeks early, now fall two weeks or more early! If the seasons are changing, who really has the omnipotence to predict what will happen next? If somebody is messing with our weather, they know not what they do for short term side effects nor long term consequences. . .


  4. So I live in growing area 10b, what are the best kinds of iris for me to grow? Jeanette from LA


    • Hello Jeanette, Thank you for the comment. Your question intrigued me and prompted a quick Google search. I came across a lovely blog with information on growing Bearded Iris in the deep South. Here is the link: I recommend a complete read of her home page introduction. I found it informative, touching and entertaining. If you click on the “Iris Directory” at the top (or bottom) of the home page, you will see the list of Iris which the author (from Baton Rouge, LA) recommends for your area. We grow many of the varieties in her list: Autumn Tryst, Jesse’s Song, Jurassic Park, Cantina, to name just a few (and several of them are on currently on sale through Sept 30). You can make a list of the varieties you like from the photos in the author’s “directory”, then search for those names on our website. Keep in mind, that we have not verified any of the information offered in the blog site listed above. We only offer our own Guarantee of Quality. We do ship to Louisiana, and if the Iris are planted according to our instructions, we guarantee their survival the first year (barring influences beyond our control: unforeseen weather, illness or pest damage). I hope you find this information useful. Happy Gardening and best of luck! Keep us posted with your results.


  5. Thanks for the interesting story! I’ve been wondering about climate change, especially with the particularly wacky weather we’ve had this year.


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