Monday, July 4, 2011

Night-flowering primrose

I recently made a few posts, HERE and HERE, about the suburban wildlife sanctuary that is my parent's yard. But there's more. One evening, I purposely hung out in the backyard as dusk passed into darkness to record the opening of a very special flower; a truly spectacular blooming.

Large-flowered evening-primrose, Oenothera glazioviana. This big, shrubby and showy cultivated primrose is commonly employed in captive plantings. My parent's yard has some pleasing snarls of the stuff, and this photo was taken just before dusk. We can see the long-cylindrical slightly reddish-tinged flower buds still closed tight as a drum. Older flowers, which opened the previous evening, can be seen at the lower left looking faded and brownish. Evening-primrose flowers only last for one evening.

This VIDEO shows the almost magical opening of the flowers. I set my camera on a tripod and let the video roll. Once a flower reaches critical mass, it only takes about two minutes, if that, for the structure to go from tightly rolled bud to fully open flower. You can easily see the whole process unravel before your eyes. No sooner has the flower popped fully open than a moth shoots in to investigate. The reason that evening-primrose flowers open at night is to lure their primary pollinators, moths. The plants' flowers are noctodorous; they release a subtle fragrance at night to lure the lepidopterans. Thanks to Chris Coulon for editing my video footage.

Over 15 minutes or so, the evening-primrose plant goes from no flowers to an incredibly showy shrublet heavily adorned with large lemon-yellow blossoms. By this stage, it is quite dark outside and numerous pollinating moths will be darting about the blossoms. It is very cool to just stand by the plant and watch as the blossoms POP open, for that's just what they do. Apparently specialized photoreceptor cells detect shifts in light, which then trigger rapid cell expansion in the flowers and their attendant sepals. This rush of fluid engorges the cells and causes the flowers to quickly explode to life.

Evening-primrose flowers are hermaphroditic; they contain both male and female parts and thus are self-compatible. Deep in the recesses of the corolla in the center of the flower are the nectaries; the sugary goodies sought by pollinating moths. The eight stamens tipped with their pollen-coated anthers project from the flower's center. Also jutting from the depths of the flower and projecting further outwards is the style, which is capped with a curious four-parted stigma. The style and its stigmas can be seen at the bottom of the flower, laying lax against the petals. It is the stigmas that must receive the pollen from the anthers in order for the plant to be successfully pollinated.

And here is one of the animals that the flower tries so hard to woo - a moth. As soon as the blossom opens, it begins to emit a subtle but distinct fragrance and the moths waste no time investigating. Moths are perfect for this task, and the beauty of evolution has wrought a harmonious relationship between two very different organisms.

Drawn by the flower's odor, the moth navigates to the center of the bloom and plunges its long threadlike tongue deep into its depths to reach the nectar. Well, as anyone who has ever observed a moth knows, they are somewhat clumsy and quite fluttery - hardly the exacting aerialists that hummingbirds are. So, in the process of nectar-diving, the somewhat oafish moth bumbles into that mini forest of stamens and their pollen-dusted anthers. Pollen then adheres to the insect's fuzzy body. Further bumbling by the moth is likely to cause it to glance off the dangling stigmas as it drops from the flower once it has sated itself with nectar. Thus, in the blink of an eye the unsuspecting moth transfers the pollen to the necessary receptors and that will eventually lead to fertile sed and new evening-primrose plants.


Lisa at Greenbow said...

It was fun watching the video of the primrose opening. It seems like if you watch yourself you blink your eye and you don't get to see it actually open. I have enjoyed the garden tour at your parents home. Their garden is fantastic.

Jim McCormac said...

Glad you like the "garden", Lisa - many neat and formal gardeners might turn up their noses, but they also wouldn't have all of those cool critters!

Scott said...

Great post I missed this in the lead up to the Midwest Native Plant Symposium.

Anonymous said...

We have an evening primrose with leaves with jagged edges about 1/2 inch wide by 6 inches long. The flowers are light yellow as yours.
We live in Ohio. We planted one last year but it didn't come back this year. Is this plant a perinneal or an annual. Or is it not in the right zone in Ohio to be a perrineal

Anonymous said...

I live in Ontario, which is not too far from Ohio. I was told that it might come back if protected from the weather. It was frozen over for a few weeks this winter however & still came back. The first year I had it I brought it inside to overwinter it. Not anymore!

Anonymous said...

Thank you for the information. I have a ton of these that just appeared in my garden a few years back. Each year they multiply. I am glad that I made the decision to leave them as they are beautiful!