When Nature Comes With Strings Attached

Pollen strands of a pink evening primrose ~ Oenothera speciosa
Bayou Bend State Park

The Oenothera genus contains about 125 species of flowering plants; pink evening primrose, beach evening primrose, and sundrops are especially common in Texas. Their flowers open primarily in the evening, and are pollinated by a variety of bees and moths.

Because the pollen grains of these flowers are loosely linked by threads of a substance called viscin, only bees with specialized pollen-transporting hairs can gather their pollen effectively. Viscin, a clear, tasteless, sticky substance not only holds the pollen grains together, it also helps attach the pollen to visiting insects.

Some botanists theorize the plants evolved in this way to allow the pollen to stick onto insects that aren’t necessarily designed to carry pollen—especially nearly hairless creatures such as beetles. Other plants in the Onagraceae also have viscin threads, although some—like those found in Fireweed (Epilobium angustifolium) — can only be seen with  magnification.

Pollen strands of a beach evening primrose ~ Oenothera drummondii
Galveston Island dunes

Beyond the viscous pollen strings Oenothera species have developed to aid their pollination, at least one of their kind has evolved another trick for tempting insects to stop by. Scientists have found that Oenothera drummondii, the pretty beach evening primrose, can increase the sugar content of its nectar within three minutes of its flowers being vibrated by visiting bees.

How the scientists figured that out I can’t say, but its very improbability makes me smile. It seems some flowers actively invite bees to drop by for a sip of nectar, as well as a little packet of pollen to go.

Comments always are welcome.

60 thoughts on “When Nature Comes With Strings Attached

    1. When I saw those pollen strings on the pink evening primrose, my first thought was of being ‘strung along,’ but a little thought turned it into the title I used, and I agree that it’s just right. I’m glad you enjoyed it.

    1. They do. When I came across the pink evening primrose at Brazos Bend, I was casually photographing it as a record of a late flowering until I noticed the neatly arranged strings of pollen. Those enticed me into spending even more time with it, and then doing some research about a phenomenon I’ve noticed in the past, but not explored.

  1. Isn’t nature inventive? The threads that don’t have hairs developed a stickiness, so it increases its chances of pollinating. Then, the primrose releasing a nice, tasty sweetness when it gets vibrated by bees. We ought to thank nature.

    1. There are mysteries galore out there — and when some of the mysteries are explained, they’re no less wonderful. I’ve found that knowing a bit of the science behind the beauty adds to my pleasure; it never subtracts.

  2. I do like the pale pink on that pink evening primrose. That feedback loop that is evolution works between bugs and blooms as well as it works between predators and prey. The more “likes” a flower has, the more likely it’s likely to come up in a random meadow search.

    1. I’ve been smiling at your comment since I found it. It’s not what you said that brought the smile, but what you didn’t say. My very first thought when I saw those primrose pollen strings stretched between the flower’s anthers was of holding a skein of yard for my mother while she rolled it into a ball. I’d bet reading a certain knitting blog helped that memory to surface so quickly.

    1. Clearly, those plants that surround us are up to more than we realize. I’ve known that things like resurrection fern can rehydrate almost immediately after a rain, and that some buds open so quickly they can be watched like a time lapse, but the thought of a flower increasing its sweetness is amazing. Of course, those flowers last for only a day, give or take, so they don’t have much time to cook up an inviting treat!

  3. The myriad strategies plants have evolved to succeed in their spread is amazing. Today I experienced, not for the first time, a little of that evolution while cleaning up around our wood chip pile. After picking up the debris the brush cutter left behind, my fleece pullover was covered with literally hundreds of tickseed travelers. Talk about prolific.

    All the evening primroses I see here are the yellow species. Pink would be a nice addition.

    1. The pink evening primrose is one of our earliest spring bloomers, and it can overspread roadsides and fields as dramatically as bluebonnets and Indian paintbrush. Your encounter with the tickseed reminded me of the day I ended up in the same situation. At the time, I was traveling in Kansas and couldn’t get back in the car carrying all those seeds, so I did the only reasonable thing and changed clothes in the Pawnee Rock parking lot: easy enough to do since there was no one else for miles.

      1. Next time, if there is an audience or not, a common fine tooth comb does an excellent job of removing the majority leaving only a few to pick off by hand. There were so many that it looked like I had an encounter with some sort of alien porcupine.

    1. Since starting this blog, I’m looking a lot more closely at the natural world, too. Most of the time, I’m doing at least a little research for each post, because I’m constantly looking at this or that and thinking, “Well, for goodness sakes. What is that?” or, “Why do you suppose that’s happening?” If I’d been this interested in such things when I was in high school, I probably would have gotten better grades in 10th grade biology!

    1. The good news is you don’t need to worry about pollen from these flowers; like goldenrod, they aren’t wind pollinated. The ragweed, sumpweed, and such? Those are demons, and in the spring there’s the tree pollen, but you could bury your nose in these and emerge unscathed.

    1. There sure are. Not only that, I’ve learned yet another way to identify members of the Onagraceae. Today, I found a non-primrose member of the family by looking for the telltale sign; I’ll be posting a photo of it before long.

  4. Wow. I was totally unaware of the pollen threads. I always thought that I was seeing spider webs woven by spiders hoping to catch the insects visiting the flowers. I’ll have to keep my eyes peeled for this feature of the primroses. And the research on upping the sugar content of nectar is fascinating. Thanks!

    1. When I first noticed the threads, I had no idea what they were. Eventually, I began seeing more of them, and went searching for information. I didn’t have to search long; it seemed that everyone in the world but me knew what they were! Well, at least a good number of botanists knew. When I finally came across the pink evening primrose with those wonderfully distinct threads, I knew it was time for a post!

    2. Me too – it’s fascinating to learn that these aren’t pieces of spider-web. I’d never heard of viscin before, now I’ll be on the lookout for it.

      1. From what I’ve read, viscin has a number of roles. For example, it’s what helps bees that carry packets of pollen hold those ‘packets’ together. So, it’s not just the strands; it’s the underlying substance that allows the pollen to accumulate in strands. I just was looking around a bit to confirm that, and look what I found! It’s visual proof of the strands’ utility.

  5. Isn’t evolution fascinating, Linda. More and more has been learned about how plants respond to insects, either an attractive way by adding sugar, or a negative way, increasing toxins in an amazingly short time. Either come hither or go away.
    On another note thanks for the information on the strands, I wasn’t aware of that and would have passed them off as spider webs. –Curt

    1. What’s even more fascinating is how long people have been observing and studying those plant/insect relationships. One of my favorite books is a 1900 edition of Nature’s Garden, written by Neltje Blanchan. The subtitle was “An Aid to Knowledge of Our Wild Flowers and Their Insect Visitors.” Of course she didn’t have all of the scientific techniques available to her that we have today, but she was a sharp observer, and that went a long way.

      Her books actually are very good, but she did have a bit of an “in” — she was married to publisher Frank Nelson Doubleday, who no doubt offered encouragement and tips.

  6. Such a great post, Linda–wonderful photos, as usual. That’s really interesting about the increase in sugar. Bees-n-flowers, they’re good companions!

    1. There are so many interesting things to learn. I finally found goldenrod in bloom today, and believe me: the bumblebees were having a feast! I came across multitudes of gaura at Galveston State Park today and thought of you. The flowers there clearly are coming to the end of their season, but there were plenty to enjoy. I don’t know why they seemed to have disappeared from Brazoria, but on the island they were plentiful.

    1. I did read that beetles and other insects could navigate among the strands quite well; the stickiness allows the pollen to cling to them so they can carry it off to other plants. The next time I find a flower with these strands, I’ll engage in a little experimentation, and see how easily they cling to a finger.

    1. I had no idea about all this until quite recently. I’d observed the strands, but it took a while for me to do the research to find out what they were. I was greatly surprised to find quite an online literature about pollen strands — including a good number of articles that were entirely above my pay grade!

  7. I for one didn’t know all this, Linda — thank you for helping educate me today. I never would’ve dreamed plants would “invite” pollinators to drop by for a take-out order!

    1. Isn’t that fun? And just think of how much work it must have taken the scientists to figure out what was happening. Thanks to the internet, we can profit from all that knowledge the specialists gain. Sometimes it takes a few tries to get where we want to go, but in this case, all I had to do was type “pollen strands primrose” into the search engine, and voila! Information!

    1. One thing I’ve noticed is that the freshest flowers don’t have these strands. It seems to take some time for them to develop. Of course, the various evening primroses only have a day or so to get pollinated, so they have to work quickly. The next time the pink evening primroses are in season and some are around for frequent checks, I’m going to watch a few and see how long it takes for the strands to develop. (If only I still were in school — it would make a great project!)

  8. The more we look the more we see. The more we see the more we learn. The more we learn the more we want to know.

    Thank goodness for a “Nature Detective” such as you to interpret clues and send us back outdoors to see and learn more.

    Yet another use for this macro lens!

    1. I do love my macro lens, especially when I remember that it’s good for more than flowers that are a foot away. Of course, I’m never without my telephoto lens, either. It’s not exactly a ‘birding lens,’ but it’s good to have when that bit of pink glimpsed through the reeds turns out to be a pair of foraging spoonbills rather than a hibiscus!

      And there’s this: sometimes, it’s hearing that piques interest rather than sight. When I was out on the salt marsh Sunday, I heard a bird whose sound I didn’t recognize. It wasn’t a song, but a repeated buzz. Another clue!

  9. I did not know about pollen strings. I always learn something here. And it doesn’t surprise me a bit that flowers react to the visits of bees. Everything is connected, everything is sentient and reacts to its environment and other life. Of course flowers would encourage bees.

    1. I can’t quite remember the details, but I do know that I’ve read about flowers that provide ultraviolet colors, too. Apparently they serve as ‘landing strips’ as the insects fly in. I suppose there aren’t teeny little helpers with those light sticks to direct the traffic, like at a real airport, but it’s fun to imagine.

    1. That’s true. The arts and sciences work hand in hand — any painter who’s mixed pigments understands that. And knowing that a flower’s pollen strands help out the pollinators makes the process more interesting, not less. Of course, when it comes to science amplifying beauty — think about the various space telescopes, and that they’ve shown us about the galaxies. Galileo would drool!

  10. I would have thought those strands were spider webs – learn something new. And it’s not even a spider plant.
    I wonder if spiders are considered spreaders of pollen? A lot of them have little hairs on their bodies too.

    1. As I understand it, spiders aid pollination indirectly. For example, crab spiders spend a lot of time lurking in flowers, waiting for prey, and in the process they pick up pollen and spread it around. Beyond that, various spiders consume other insects that prey on bees, and that helps the bees do their thing. There are a lot of interconnections!

    1. After I learned that viscin plays a role in pollen strings and in holding together the pollen ‘packets’ that other bees carry, I wondered what other functions it serves. As it turns out, it’s present in mistletoe berries; each berry can produce up to two metres of the gluey threads, allowing the seeds of the parasitic plant to stick to and infect host plants. There are scientists exploring biomedical uses of viscin; there’s an article here that’s relatively short, and might be of interest.

  11. Absolutely fascinating! Like Dave Ply, I’d have thought those strands were spider silk. I learn something new just about every time I read one of your posts. Thanks much for that!

    1. I just learned something else about viscin; it’s what allows the berries of the parasitic mistletoe plant to adhere to host plants. Beyond that, scientists are exploring biomedical uses of the substance. It is fascinating; I can’t wait to find some mistletoe berries and check out that stickiness.

    1. One of the fun things about teaching is that the teacher gets to learn, too! Since posting this, I’ve found something else interesting about this genus. Look at the second photo — see how the stigma is divided into four parts? That’s characteristic, and when I saw the same thing in gaura flowers, it made sense that that plant has been moved into the primrose family!

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