Sunday, June 23, 2024

Plant story-- Eriogonum alatum, winged wild buckwheat

This is a post about a plant almost nobody has ever seen, let alone noticed. Winged wild buckwheat, Eriogonum alatum (buckwheat family Polygonaceae) has its range at low elevations on both sides of the Rocky Mountains and into Utah. Lots of people live in that area, but nothing like the number who live on the East or West Coast, so the number of locals who could know it is limited.  

Winged wild buckwheat, Eriogonum alatum in flower
Winged wild buckwheat, Eriogonum alatum in flower
(yellowish, center)

Most of its life, winged wild buckwheat is a circle of leaves on the ground (rosette), easy to overlook or misidentify as some other plant. 

Eriogonum alatum rosette, starting to bolt (flower)
Large rosette, starting to bolt (send up a flower stalk)

Then, some June when it is 2, 3 or 4 years old, winged wild buckwheat sends up a flowering stalk (bolts).

Is it more visible when bolting?  

No. A single yellow-green stalk, the yellowish flowers 1/8" across and sparsely distributed across a the much-branched stalk, it is quite hard to see. Your eyes look past or through them, to more solid plants.

Winged wild buckwheat Eriogonum alatum, flowering
Winged wild buckwheat Eriogonum alatum, flowering
I walked into a place where I had studied winged wild buckwheat in the past, looking for them. I saw none. Then I walked smack into a flowering plant, three feet tall, before I saw it. They hide in plain sight.

The buckwheat that we eat (Fagopyrum esculentum) is a Middle Eastern relative of the wild buckwheats (Eriogonum) of North America. There are about 250 species of Eriogonum, 244 in North America. After Penstemon, Eriogonum has the most species of any genus native to North America. The name Eriogonum is from erion, wool, and gony, knee, in Greek, referring to the hairy nodes of the first Eriogonum species given a scientific name.

The species epithet alatum means winged. That refers to the seeds, which have three papery "wings" around them, presumably to let the wind carry them farther from the parent plant. 

Eriogonum alatum winged wild buckwheat seeds
Eriogonum alatum winged wild buckwheat seeds
seed surrounded by "wings" 

I have studied winged wild buckwheat off and on for more than 20 years and can fairly say I am the world expert on the plant. Not that anyone knows or cares.

Why do I care?

Because I am drawn to puzzling plants. The vast majority of plants flower multiple times, every year for 300 years for oak trees, for example, twenty years for a peony, a dozen times for a rosebush. Not winged wild buckwheat. It lives for several years but it only flowers once, and then it dies.

That life style, called monocarpic in plants, semelparous in animals, is not particularly common. Botanists find it most in environments where survival over the bad season (winter, or the dry season, for example) is poor, so plants that throw all their stored energy into seeds, rather than save some energy for next year, have more successful offspring. (Think of it this way: the stored energy could not save the parent plant, but it did make more seedlings, at least one of which survived.) 

Winged wild buckwheat grows in a region that has low rainfall and is prone to drought, but there are other wild buckwheats, for example Eriogonum umbellatum, called sulphurflower buckwheat, which are native to the same places but live normal, multiply flowering lives (called polycarpic in plants, interoparous in animals).

sulphurflower buckwheat, Eriogonum umbellatum
sulphurflower buckwheat, Eriogonum umbellatum,
a normal (polycarpic) perennial, it flowers every year after it reaches maturity

Flowering is about reproducing, making seeds. Monocarpic flowering seems perilous because the plant has a single chance to flower out of a several-year lifetime. What if other members of its species flowered the year before or the year after? I've always liked imagining it: you stake everything, the one flowering opportunity of a lifetime, on a particular year, but being a plant, have no way to know whether or not any other members of your species are flowering. Until pollen arrives on your stigma, ahhh!!!!, but that is weeks after you committed to flowering this year.

Eriogonum alatum, winged wild buckwheat
Throwing everything into one flower stalk.

Perhaps in most years, a few winged wild buckwheat plants will flower so the plant rarely makes a mistake and flowers alone. Also, it is likely that all the plants use the same, particular cues for flowering, so if one puts off flowering until next year, most others will do the same.

But wait, winged wild buckwheat isn't just monocarpic, it is dioecious. Each plant is only one sex, so no seeds will be set if a plant flowers alone. (Many weedy species self-pollinate so do not require a mate.) In winged wild buckwheat, some plants have flowers that lack pollen (are "female") others have flowers that have pollen but no ovary (are "male"). Structurally they are not suitable for wind pollination, so a pollinator--an insect--has to carry pollen between different plants scattered in the grassland. And only half of the plants flowering are suitable mates.

Most plants have perfect flowers (male and female parts within the same flower) or at least, like pine trees, both male and female flowers on the same plant. Not winged wild buckwheat.

So it must pick a "good year" to flower and also trust that others of the opposite sex will be there.

Eriogonum alatum winged wild buckwheat
winged wild buckwheat. These flowers are female (no anthers with pollen)
Note the insect visiting (pollinating?) the flowers near the bottom

I've counted and measured winged wild buckwheat plants and I will publish the data I collected. I have seen tiny insects visit the flowers. I can tell you that a rosette with 10 leaves is too small to flower, but that most rosettes with 30 leaves do flower, and that they are generally 1-2 years older than plants with 10 leaves. Populations have more female plants than male plants flowering, year after year, and despite most plants being unisexual, a few, say 10%, have both kinds of flowers, some that produce pollen and others that produce seed.

I don't get it. Why not be a normal plant, flowering every year, each flower both male and female? Winged wild buckwheat is doing ok. It can be quite common on the open gravelly slopes it prefers. I've  retired from experimental botany, but I'll put my studies into a publication so that, in the future, someone can fill in the missing pieces and tell the full story. What evolutionary edge does its curious reproductive cycle give winged wild buckwheat?

As a general conclusion, though, for everyone who doesn't live where this hard-to-notice plant is found, is that somenondescript little plant you've always walked by will be fascinating if you learn more about it.

(What might I find fascinating? Pollinated by beetles (red trillium). Too poisonous for all but one native bee to pollinate (death camas). Seeds dispersed by ants (violets). and more)

Comments and corrections welcome.

Eriogonum alatum, winged wild buckwheat

A few more photos. Sometimes I can get an angle which makes them obvious, or at least visible.

Eriogonum alatum, winged wild buckwheat
Eriogonum alatum, winged wild buckwheat
one in the center, two smaller others flowering on the right side of the photo

Eriogonum alatum, winged wild buckwheat
Eriogonum alatum, winged wild buckwheat flowering

Comments and corrections welcome.


Reveal, J. L. Eriogonum Michaux. Flora of North America link (accessed 6/22/24)

Kathy Keeler
A Wandering Botanist

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