Dandy Dandelions

by Dana Atkinson | May 1, 2024 | 0 comments

Yay, the dandelions are taking over! I thought as I glanced out the window one May day.

Actually, I’m not crazy; I’m just kidding. Seriously though, I do wonder, “Does, ‘In everything give thanks’ apply to dandelions?” In case it does, I might as well name some dandelion blessings one by one.

First, I’m amazed at the Creator’s ingenuity when I think about how those dandelions got to my yard in the first place. Most likely they came soaring like eagles from some neighbor’s yard. That neighbor could even have been enjoying blowing on a dandelion seed head like you might soon be doing in order to observe a dandelion seed’s incredible, precise, 100-bristle, vortex-enabled, seed-transporting flight system.

Each seed can come riding on the breeze because of an informed deployment of its whorl of bristles that causes an area of stalled, recirculating air called a separated vortex ring. This vortex’s area of low pressure causes drag (the force operating against the seed’s downward motion caused by gravity). In other words, the separated vortex ring acts like a parachute made of air. Also, and very importantly, the vortex provides stability to the seed so it can remain afloat for long distances, provided there are updrafts. (Riding updrafts is where soaring like an eagle becomes a comparison.)

dandelion bristles in candle smoke
Dandelion pappus in candle smoke. Photo © Dana Atkinson.

Here’s a picture of the separated vortex made visible by holding a dandelion pappus (the whorl of bristles) in rising candle smoke. I can imagine two areas of elongated circles of smoke particles circulating inside the “dead area” because I’ve seen more detailed photos researchers have taken of the phenomena using wind tunnels, laser beam splitters, and special camera equipment.

Now about those 100 bristles. Around 100 is the optimal number of bristles. More than that would make a dandelion seed’s flight unstable, and less would not create enough drag for flight.

The formation of the separated vortex ring also depends on the angle of the bristles, which is what the informed deployment is all about. When there is dew, high humidity, or rain, each pappus will close up somewhat like an inverted umbrella, resulting in very bedraggled-looking seed heads. The moisture-sensitive actuators have turned off the dandelion seed flight mechanism.

When the weather is dry, the moisture-sensitive actuators redeploy the pappi to catch breezes and updrafts to soar away and disperse seeds. Dry, sunny days are conducive to thermal updrafts. That’s when eagles soar and my dandelion seeds head for who knows where.

Dandelion seeds flying
Dandelion seeds flying. Photo © Dana Atkinson.

In order to see this totally amazing process on my timetable, I’ve gently misted the fully deployed, intact seed heads with a hand sprayer. In a matter of minutes the pappi began closing. The process of redeploying takes a while longer to open back up. This weather-dependent deployment system has been described as a ‘radial tubular actuator’. The actuator’s mechanism operates due to differential swelling of four different plant materials. Some parts of the seed head absorb moisture and swell outward. Other parts resist swelling and act as anchors to lever the attachment points of the bristles so that the bristles close up. All in all, the dandelion has a very ingenious passive flight system.

Secondly, dandelions display clocks which are a reminder that the Creator appointed the “sun to rule the day.” I see clockwork when hordes of dandelions take over our yard in late April and May. Also, like clockwork, they pepper the yard with yellow late in the morning. Their flowers display this daily clock by closing at night and reopening by mid-morning. So, one way I could be okay with a yard full of dandelions is to admire my green yard early in the morning and just ignore it after late morning.

Thirdly, when dandelions take over the yard, there are direct and indirect benefits to people. For instance, dandelions can take over meals. Have you ever had dandelion ‘coffee’? Dandelion greens in salad? Batter-dipped, fried dandelion flowers? Honey? Yes, dandelion nectar and pollen are part of the support system for honeybees. Check out the photo of the honeybee covered in pollen as it is nectaring on a dandelion—that’s honey in the making!

honeybee on dandelion
Honeybee on dandelion. Photo © Dana Atkinson.

Interestingly, the common dandelion produces seed without the need to be pollinated, but it still produces pollen. (Common dandelions are apomictic triploids, in case you want to look it up.) The dandelion probably receives little, if any, benefit from producing the nectar and pollen, but they have friends that surely do—friends like butterflies, solitary bees, and ants. Even birds benefit from dandelions. I’ve seen sparrows and finches hop onto dandelion stems, tip them down, and then commence to feed on the dandelion’s seeds.

Dandelions do have enemies. I have seen deer, other wildlife, and various farm animals browsing on dandelions. I’m using browsing in the sense of taking a nibble here and there; it’s not like they are feeding solely on dandelions. This can be attributed to the dandelion’s chemical defense, which is that milky white latex that oozes from their stems. That latex is the dandelion’s deterrence against herbivory. Some people champion the compounds and chemical properties in dandelions and their benefits in things like health foods, medicines, and rubber tires.

Anyway, there are more dandelion blessings, but I’ll stop here before you conclude I was seriously rejoicing about the dandelions taking over my yard. Oh, but in defense of those dandelions taking over the yard, I must say, “That weed is a dandy!”

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