…But Sometimes They’re White

I generally use this blog platform to share ideas and information about prairies, but now and then I also use it as a platform for asking questions.  Today is an example.

I want to know why many wildflowers, especially those with pink, blue, and lavender-colored blossoms, sometimes produce white flowers.  As far as I can remember, I’ve never seen a white sunflower or goldenrod flower, or a white variety of any flower that is normally yellow, orange, or red.  However, it’s not that uncommon to see white gayfeather, verbena, or spiderwort blossoms.  What’s up with that?

Dotted gayfeather (Liatris punctata), showing the the typical pink flowers on the left and a white variant on the right.

I’ve looked for information on this, and talked to a few friends with horticultural/botanical knowledge, but haven’t really learned what I want to know.  I’m interested in the mechanics of how these typically pink or bluish flowers turn out pink, but I’m actually more interested in why it seems not to happen with all species – especially those with yellow flowers.

Prairie gentian (Eustoma grandiflorum) might be the species with which I see this phenomenon most frequently.  It is an annual/biennial that is typically purplish in color, but whenever I find a big patch of them, I can usually find a few plants with white flowers.
Spiderwort (Tradescantia bracteata) sometimes has white flowers – I used to have some in my home garden.
Hoary vervain (Verbena stricta) can sometimes have white flowers as well.  I wonder if the white blossoms are any more or less attractive to pollinating insects?

In addition to wondering about how the white flowers occur and why it seems to happen mainly in bluish and purplish-flowered plants, I’m curious about a few other things.  Is the white color variant recognized differently by bees and other pollinators?  Are there other differences (nectar or pollen amounts, odor, or flavor) that correlate with those color differences?  If you harvest seed from the white flowers, do at least some of them grow into more white flowers?

Pitcher sage (Salvia azurea) and bumblebees.  Most pitcher sage plants are blue, but at least a few grow white blossoms now and then.

I’d sure appreciate any insight on these topics.   I was surprised not to find answers readily available online, but maybe I just wasn’t framing the questions correctly?  Thanks.