Dallas Morning News - May 8, 2019
Flowers Changing color – Magic?
Garden writers and other "experts" say the flowers of plants cannot change color – except for hydrangeas.
In Dallas' alkaline soil, hydrangea blooms are pink. It's an old-fashioned custom to apply acidic amendments regularly to the soil at the base of the shrub to produce blue flowers
Big-leaf hydrangeas, the ones with large showy flowers (actually bracts) are said to stand alone in ability to change bloom color. In acidic soil (pH below 5.5), hydrangeas produce blue flowers. In neutral to alkaline soils (pH of 6.5 and higher), flowers are usually pink - supposedly because higher pH makes aluminum in the soil unavailable to the plant. My experience is that changing the color of these plants by adjusting soil amendments is possible, but mostly the results turn out to be a rather dull color somewhere between blue and pink.
Related to other plants, some horticultural geniuses say it's just a figment of the imagination that flowers can change color - doesn't happen in nature and can’t happen in your garden. That's not true. Flowers can definitely change color, but it is a little difficult explaining how it happens.
Doubters will say that if an iris or any other plant changes color, it could be a combination of things or simply a random accident, but it's not the plant actually changing color. Attempted explanations range from a rogue rhizome of white irises getting in the blue/purple iris bed and taking over to you just forgetting what you planted and where.
Some will admit that flowers can have a slight color change or loss of color, due to extreme temperature changes or a change in light conditions because the nearby trees got bigger. Deep purple irises commonly turn a lighter color when maturing and starting to die. It is also said that these color changes usually revert back over time and the plant will resume its usual color. Unexplained instances of an entire bed that was purple turning white the following year just can't happen they say. But it can. Happened at my office. When we bought the place, the iris bed in the front yard was all blue/purple. The year later it was all solid white - and I didn't do anything to the bed other than start fertilizing with the organic fertilizers I use generally.
Crinum lilies can change color from one season to the next
Several of my listener/readers have reported similar cases and results. My buddy and co-organic-conspirator on the radio in San Antonio, Bob Webster, has had personal experience and many reports from others about this curious flower color change.
The case that confirmed my strong suspicions happened in my own back yard. Bright pink crinum lilies where planted in early spring and bloomed that first summer with gaudy hot pink flowers. The next season they were white with pink stripes and for the last five seasons they have bloomed a beautiful pure white.
Don't try to figure it out – just enjoy it.