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.
The Prairie Ecologist 
What a great question. I have noticed this even in the ubiquitous patches of red clover near my house – once in a while, the plants churn out a white flower. It hadn’t occurred to me that there might be something larger going on. And then there are the Purple Prairie Clovers and White Prairie Clovers – separate species, but to my unscientific eye, pretty similar….perhaps the color variation played a role in one species eventually becoming two?
white prairie clover is Dalea candida, and purple prairie clover is Dalea purpurea. The white species is larger (and coarser in my appearance) than the purple.
I recall reading a long time back that pink, blue and purple flowers may be able to produce white flowers but for yellow flowers it was a rarity. Here’s a bit of history on white marigolds
“The first French marigold with really, really white flowers was created in 1975 by home gardener Alice Vonk, who won $10,000 for her efforts from the Burpee Seed Company. (To generate interest in French marigolds, Burpee had announced the competition in 1954; however, no one until Vonk produced a marigold with pure white—not ecru or ivory—flowers.)”p
We have the same phenomenon with our ceanothus here in the Sierra Nevada. Good question.
Interesting thought! Hardenbergia violacea (local to our region of Australia) is one that occasionally throws out a white form.
I am not a plant geneticist by any means, but perhaps something can be gleaned from this paper, or by snowballing down to some of the cited papers.
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0013230
Hope this helps a bit Chris!
I think you are talking about genetics here, reminds me of biology class with the different colors and their inheritance methods. Not sure what the initial reason for white variants in these particular colors would be though, but good investigative questions!
I have a white flowering Pitcher Sage plant in my garden. Every year (for 5 years) I collect the seeds from this plant and attempt to answer this same question. So far all of the plants I have started from these seeds have bloomed blue. I have also noticed that the germination rate isn’t as robust and the plants are slower to mature some times taking 2-3 years to bloom…. if they survive.
I’ve wondered if two plants with white flowers were isolated so they were only pollinated by each other what would happen.
I cant get the bees to help me out on this. Seems they have their own agenda.
It might help if you would pollinate some specific flowers on the plant (if you only have one plant you would be “selfing” the plant). It might not work, some plants refuse to accept their own pollen. Also you would have to protect the flowers you want to set seed from being pollinated by other sources (bees, etc) before and after you pollinate the plant.
I’ve found several species with white examples: the prairie gentian you mention (including some pure white), the meadow pink (Sabatia campestris), basket-flowers, and Texas’s beloved bluebonnet.
When I was trying to figure out the white prairie gentians, someone told me the dynamics are the same as with white bluebonnets. The white flowers result from a mutation in one of the genes responsible for producing their usual color, but the breeding isn’t true. In a field filled with colored flowers, white flowers most commonly are pollinated from the purple, masking the mutation in the next generation and producing more colored flowers.
Some white ones will surface occasionally since blue flowers can carry the mutant gene that causes white flowers. But to produce white flowers, an egg with the white mutant gene must be fertilized by pollen which also has the mutant gene. That’s apparently why white flowers sometimes will form small colonies; as their numbers increase, the white parent flowers have a better chance of being fertilized by pollen that carries the mutation.
Jerry Parsons at Texas A&M is the white bluebonnet guru.There’s an interesting article here. It’s a little old, but tucked in the middle is this:
“When attempting to locate and gather seed of the white bluebonnet population… people were told only to collect seed from whites in large groups so that natural selection had already bred some of the blue out of the white.”
“The genetics of the whites were not clearly understood and we did not know exactly how many white blooming plants would be produced when planting seed collected from white bluebonnets. Many skeptics indicated that it would take years to successfully complete the purification of a white strain. The first season that white seed were collected and planted, 75 percent of the plants produced bloomed white the following year. “
I think the reason is pollinators of pink/blue/lavender flowers are less specific on color or the plants are less specific on a pollinator (for example butterflies vs. moths). In contrast, the pollinators of yellow/orange/red flowers are in various degrees more specific on color. Many yellow/orange/red flowers do have white individuals. It is just much less common for yellow/orange/red flowers to be white because of this higher degree of selection against the trait.
FYI There is a white goldenrod in my area. It is Oligoneuron album. The USDA says this one makes it to every state around Nebraska and Kansas, but oddly enough it is not found in either of these states.
Chris,
Several years ago I found and photographed a solitary white variant of what I believe to be a purple prairie clover (Dalea purpurea) growing in a pure stand of the normal purple variety in a remnant prairie in southern Wisconsin. The anthers on the white specimen were all brilliant orange, but the flowers were otherwise all white. The anthers of the typical purple form of Dalea purpurea are bright orange, whereas the anthers of the white prairie clover (D. candida) are typically whitish to pale green. In a sedge meadow on my property here in southern Wisconsin I have also discovered a healthy stand of white variants of spotted Joe-Pye-weed (Eupatorium maculatum), growing amidst many plants of the typical pink form. The white Joe-Pye-weeds have persisted since at least 2011.
We always had one white tulip show up in our small bed of red tulips. I have a question for you. Do you see these at the same time? A colored flower by a white one?
I have encountered white cardinal lobelia and white Indian paintbrush, but they do seem quite rare, relative to how often I see white versions of pink to blue flowers.
Interesting anecdote: One nice spring day, I was observing insects and the odd hummingbird or two visiting a big population of Indian paintbrush that was about half red-orange-flowered and half pale yellow. Bumblebees (which don’t perceive red) seemed to be indiscriminate about which color morph they visited, simply flying to the next plant, whatever color its flowers (well actually, its bracts). Meanwhile, swallowtails and the birds showed a definite preference for the redder version, with hardly any visits to the pale yellow ones.
It was a very good year for Rocky Mountain Beeplant in my area and I noticed quite a few white variants of that plant this summer. I’ve seen a couple white variants of the other flowers you mention as well. I guess I’ve always assumed it was a bit like blue eyes or red hair in humans, just a recessive trait that sometimes pops up but I can’t say I’ve really thought much about it. However, I have seen before an annual sunflower growing in Rock county that wasn’t quite white, but a very pale cream. It was only one plant growing along a road and that’s the only individual I can recall ever seeing like that.
Could this be that somewhere in their genetics a gene is present and have a probability of expression?
I wonder if it could be just a defective enzyme in the individual plant due to some other developmental influence, and not related to genetics at all. Also, insects possibly see these flowers different then we do, so the “color” apparent to us may not influence their choice because they are using different triggers.
Here is something else to read:
https://www.scientificamerican.com/article/bring-science-home-flower-pigment/
At one of our preserves in Minnesota, we found a white milkweed. It was found in a patch of other milkweeds, but this was the only one that was white. One botanist told us it may be some sort of mutation where chloroplasts are lost during the process of vegetative spreading. The plant can still survive because the plants joined by rhizomes help keep it alive.
A colleague, Robert Wyatt, commented: “I think that plants with all white flowers in normally colored species usually represent mutants that have a block somewhere in the metabolic pathway that produces the pigment. And you may get the same effect, even if different mutations are involved. In most cases, I would guess that such plants might receive fewer flower visits from the normal pollinators than plants with colored flowers. They would then produce fewer seeds and, over time, be eliminated from the population. Now, as to yellow flowers not being subject to the same scenario, I am not sure. I do know that many mustards that normally have yellow flowers often have white-flowered individuals show up (such as wild radish in California, which has been much studied). It could be that these individuals are not at so great a fertility disadvantage as the pollinators may not really distinguish between the two morphs. It may also be that UV patterns are the same in white versus yellow flowers. Another group in which there is considerable variation in yellow versus white flowers is Leavenworthia, also a mustard (and a native to North America).”
I harvested some white Verbena stricta from our pasture this year and plan to seed it in Lincoln next year. I’ll let you know if it’s color is true. I have planted seed from a pink colored Verbena stricta and it bloomed pink in Lincoln (160 miles from collection site). I’d be happy to share some of these seeds if you’d like to experiment with them.
Thanks Alison – I’ll let you handle the experimentation, but I would definitely like to hear the results!