Iris were yellow, now blue

[Phisherman]

My iris bed is in full bloom. Blossoms were yellow last year now they are blue. What causes this and will they be blue again next year?

[brooklyn1]

Some iris can behave like hydrangea, their blooms can change color with soil pH...have you added anything, mulch, new plants nearby?

[David E. Ross]

If this happened in my garden -- five different varieties of bearded iris -- I would suspect that I mixed up two varieties when I divided them last year. While the colors of bearded iris might become more or less vivid depending on weather, water, and nutrients, they do not show such substantial changes as you describe.

[Phisherman]

My neighbor has purple iris, about 60 feet away, so I was not sure if the color change was due to that(?). The iris are growing with daffodils in round bed surrounded by tall fescue grass. My neighbor has deep purple iris, about 60-80 feet away. The bed may have got some lawn fertilizer, but if not neutral the soil may be slightly acidic (I'll test it today), no mulch, no new nearby plants. Light blue is not a favorite color, but glad to see them blooming well.

[Phisherman]

Hiked to Emery Gap Falls in the Cumberland mountains this morning and saw thousands of wild iris in bloom. I noticed slight color changes from one location to another, some having yellow centers, others white, but all were blue. Darker blues where there were open canopies, and pale blues in shadier areas. Every wild iris looked like a miniature to what is in my garden.

[Fran]

[Fran]

To reply to my own response - my blue irises are done, and the yellow are starting to bloom.