Tag Archives: sunflower

Photo of the Week – January 23, 2015

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There are a few subjects I can’t seem to keep from photographing.  Milkweed seeds, for example.  Patterns of ice on frozen wetlands.  Dew-covered insects.  And sunflowers.

What flower is more distinctive?  Their bright yellow color and big round flowers stand out, even in the most showy of flowery prairies.  Insects seem to find stiff sunflower attractive too, based on the number of insects I’ve found and photographed on them.

Plains sunflower (Helianthus petiolaris) in restored sand prairie. The Nature Conservancy's Platte River Prairies, Nebraska.

Plains sunflower (Helianthus petiolaris) in restored sand prairie. The Nature Conservancy’s Platte River Prairies, Nebraska.

We’re fortunate to have seven different species of sunflower in our Platte River Prairies, five of which are perennials.  The above photo is of one of the two annuals, plains sunflower, which inhabits the drier sandy uplands of our sites and is very abundant in the Nebraska Sandhills to our north.

I have plenty of sunflower photos I like, but this is one of my favorites from last year.  I like the overall composition, but I also like that the sunflower in the foreground is atypical.  Something has prevented the petals (ray florets, for you botanists) from developing completely.  It’s interesting (and not unattractive), and also stimulates questions about what happened, and why.

I like mysteries…

Wanna Know What Really Makes A Sunflower Lose its Head?

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Nearly-decapitated sunflower heads, scattered across the prairie.  Oh, the devastation!  Who could be carrying out such an evil plan?

(Ok, more accurately, a weevil plan?)

Weevil damage

I found this sad-looking stiff sunflower (Helianthus pauciflorus) during a prairie hike back in August.

Maximilian

Stiff sunflower was not the only species being targeted.  Maximilian sunflowers (Helianthus maximiliani) were also dangling…   This photo was taken just a few minutes after the first.

The head-clipping weevil, aka the Silphium weevil (Haplorhynchites aeneus) is a small dark-colored weevil, less than a centimeter in length.  Females girdle the stems beneath sunflower heads – as well as other plants such as compass plant and rosinweed – so that the flower head falls over, but usually doesn’t drop completely off, at least not right away.  Once a flower has been knocked over, other weevils usually show up – male and female – to feed on pollen, mate, and lay eggs in the blossom.

Doing some research for this post, it was hard for me to confirm what happens next, but it seems the eggs usually don’t hatch until the flower eventually falls to the ground.  The larvae feed on the decomposing flower head and then burrow into the earth to overwinter.  It is thought that clipping the flower before laying eggs on it might make the flower a less attractive place for other insects to lay eggs, saving more food for the weevil larvae.

I have rarely seen the head-clipping weevil itself, and had never photographed it. On the day I photographed the sunflowers shown above, though, I finally saw one fly off a stem and managed to get a documentary photo of it. Look at all the sunflower pollen stuck to it!

Before that August hike, I hadrarely seen the head-clipping weevil itself, and had never photographed it. Not long after looking at the sunflowers shown above, I finally saw a weevil fly off and managed to get a documentary photo of it when it landed. Look at all the sunflower pollen stuck to it!

The clipping behavior by weevils can cause problems for those raising sunflowers commercially, but I’ve never seen it impact enough flowers to cause any serious issues in prairies.  I’m guessing that some of you readers will know much more about the head-clipping weevil than I do, and I hope you’ll contribute additional information in the comments section below.  Thanks in advance!

So, to summarize the weevil plan:  The weevil female nearly decapitates a flower and then mates with weevil males and lays weevil eggs right on the mortally wounded blossom.  The weevil babies eat the dying flower and then burrow into the ground until the next spring.  Then they make a triumphant return and hatch their weevil plans once again.  And who do we have to thank for finding out about all of this?

Weevil scientists, of course!