I have had one reversion of 'Bewilderbeast' that lost all of the purple-y spotting and streaking and became a beautiful pastel. It happened twice from single fan divisions planted in 2 different places. This was in the Rose Garden and at the Manor House on the campus of Cal Poly Pomona. The Rose Garden is a public display garden and there were no pods allowed. They both looked the same and you could still see the basic pattern but the color was completely different. It's the only incidence I can think makes any sense for this kind of change and wouldn't expect the usual "it changed from yellow to purple" or vice verse to happen.

Bewildebeast is an odd plant by its geneticts not what is usually meant by the 'change color' in plants.

Yes, it is a strange one!

this article may shed some light on the subject(s)
https://theamericanirissociety...

yea Tom. He makes very good points.

I found Kent's explanation posted a few months ago to be very thorough, and it really cleared up the color changing issue for me. I've copied his answer below:

KentPfeiffer said:It has, in fact, been solved. People just don't like the answer so reject it. I recently saw it happen to someone who lives a few blocks from me. They had a nice big clump of what appeared to be Pink Satin (it's hard to say for sure since the Sass brothers introduced several similar irises) growing in the strip between their sidewalk and the street. There's always a number of bee pods in the clump when it's done blooming that don't get removed. In 2018, a single stalk appeared in the middle of the clump with white flowers and a second one had yellow flowers. These were obvious seedlings growing within the existing clump. The homeowners apparently didn't notice because they didn't make any effort to remove the seedlings. Last year, there were a lot more white or yellow flowered stalks. By this spring the clump had about 75% white flowers and 25% yellow flowers. The seedlings were able to completely overrun the existing clump within two years of first bloom. For anyone not paying close attention, that would seem like an instantaneous transformation.

There's a couple of reasons why the supposed transformation always seems to be from purple to white or yellow. The first is that white or yellow flowered seedlings will pop up from all sorts of different colored parents. For example, if you cross a pink iris to a blue iris, you'll get a boatload of yellow seedlings, fair number of white seedlings, and a very small number of other colors. Put simply, it's easy to get white or yellow flowered seedlings from purple parents. It's more difficult to go the other way. White or yellow parents don't produce purple seedlings (unless the pollen parent provides the genes for purple of course). The second reason is that when a purple seedling overruns an existing purple clump, people don't notice. When a white or yellow seedling overruns a purple clump, it's hard to miss.

The reason why this seems to mostly happen to older irises is also pretty straightforward. In modern TBs, the gap between the fall petal and style arm is usually so large that it's difficult for bees, even big bumblebees, to deposit pollen on the stigmatic lip. Bee pods are much more common on older varieties.

I have at least a dozen examples of iris planted near other varieties that have changed to the other color. One small, pale blue iris has destroyed 5 award winning iris purchased from a reputable grower. I lost a Bewilderbeast, a black iris, and peach iris, and a white with a purple/blue edging on the petals. I have also lost a deep blue rebloomer, a fiery orange, a purple. In addition I have lost a gorgeous lavender, a magnificent blue, and an award winning yellow. I will probably be removing all these iris and starting over, not mixing plantings of any bulbs in the same bed ever again!

Margaret, make certain you are pinching off the faded blooms each day, or you can get corruption of the original clumps with seedlings, too. Irises don't change color, but the clumps can become corrupted with seedlings, which then overrun them.

Clumps should also be planted with adequate space between them to prevent one overrunning others.

Many irises are strong growers, and will over take the space where a weaker iris is growing. This isn't color change, but more of a power struggle. Like Daisy mentioned, sometimes seedlings will grow from seeds left to mature and spread, and they will sometimes overpower the original parent plant. It usually is one that is different then any you are growing, but could be similar to one of it's parents. I have had one of the broken pattern irises that had one rhizome revert back to not being broken pattern, but I understand that many of the broken pattern irises like Bewilderbeast have that pattern due to a virus, so I assume that one rhizome didn't carry the virus.

Margaret! How frustrating to have lost so many pretty irises! Daisy's advice is good---I try to pinch faded blooms regularly and look for developing bee pods and remove them, too. Some cultivars are naturally more fertile--in fact for some people who like to hybridize, this is a plus. For me, it is a negative. Sometimes iris descriptions mention fertility or lack of it ("difficult pod parent" for example----that is a plus for me! )

Tom, how do you know if a broken pattern is from a virus? That doesn't sound good. Is there a database somewhere on broken irises that gives this info?
Most pictures of broken irises don't do much for me, but there are a couple of cultivars and potential intros I am considering.

I'm not an authority on the subject of broken patterns in irises, just what I've read on here over the years. Maybe one of the more experienced hybridizers on here could be more specific. I understand that some of Paul Black's newer broken pattern irises may not be due to a virus. @KentPfeiffer May have more information on this.

I've read that as well, but don't believe it to be true. Broken color seems to be a genetic trait in most cases.

There are viruses that can cause streaking in otherwise solid colored flowers as can been seen in this picture of Az Ap:



I suspect people have conflated this virus induced streaking with the broken color pattern and erroneously passed on the idea broken colored irises are caused by viruses.

Thanks Kent for clearing that up. I've heard that broken colors in tulips are caused by a virus, If that's true, that info may have been transferred to irises somehow.

If you grew broken colored tulips, would the same virus infect the irises?

Are all broken colored tulips caused by a virus, or only some of them?

I love your new avatar Tom

There are a number of tulips that have "flames" and other types of "brokenness" that are not infected with the tulip breaking virus. A few:

evelyninthegarden said:If you grew broken colored tulips, would the same virus infect the irises?

Are all broken colored tulips caused by a virus, or only some of them?

No, I don't think the Tulip breaking virus infects Irises. It does infect Liliums, however.

Most modern broken-coloured Tulips from are genetic mutations, rather than viruses.

I have been growing Irises for about a decade now and have a whole yard full (800+) and I have never had one change colors... Well slight weather induced temporary changes but nothing permanent. Because of weather changes, sometimes they are brighter, sometimes my chartreuse Irises are much greener, and my violets are more blue. But come the next year; they can appear duller, the chartreuse tones can look very yellow and the violets may look much more purple. I love this unpredictability. Even my old clumps can provide surprises, like a large amount of blooms or extra diamond dusting: a slight change in shading, ect.