Flower color change

Perhaps you have heard people say My Asiatic lilies changed from pink to orange this year to. Or maybe this – Grandma’s rose bush always had yellow blooms, but now, her roses have turned red.

The question that comes to mind is Why would a flower change colors from one year to the next? As is the case with many horticultural questions received at ISU Extension Offices, there may be several possible reasons why a flower color change may seem to occur.

Lilies and roses do not have the true ability to make dramatic changes in color, but sometimes, color changes do appear to happen. So what is the mystery as to why a plant’s flowers would seem to have made a change in color?

With roses, the usual cause of flower color change is due to winter die-back, when the top of the plant dies. Grafted roses have stems or canes of one type of rose grafted to rootstock of a different, hardier rose, which helps less hardy roses survive our cold Iowa winters.

One way to avoid a color change of this type is to plant only roses that are grown on their own roots. Then, if the top of the rose bush dies back, any new canes emerging from the roots will be the same plant cultivar and the same color.

What often occurs when a lily “changes colors” is when a less vigorous lily is planted near another, stronger lily cultivar. This results in the weaker cultivar being over-taken and die out occurs, rather than a color change.

With hydrangeas, the soil pH will effect the color of blooms changing from pink to blue. If aluminum is present in the soil, flowers turn blue. A lower soil pH is needed for the aluminum to be available to the plant.

Insufficient sunlight can cause blooms to be of a pale, lighter hue. Flower colors will also slowly change as the bloom ages. Other reasons for color change include: temperature extremes, stress due to lack of water, insect attack, fertilizer levels (too much or little), also cause pigment changes in flowers.

And when saving seeds, remember that hybrid plant seeds will not result in the same color as the parent plants.

Did you know? Genetic mutations can occur in a plant and when this happens, a new flower or leaf of a different color, shape or form may appear on the same plant along with blooms of regular type. This type of change is called a “sport”.

Have a gardening question? For ISU horticulture advice, email photos, along with a good description of the problem to Yvonne McCormick at yvonne@iastate.edu