Category Archives: Prairie Plants

Goldenrod, Allergies, and Spitballs.

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Every year at this time, I find myself defending goldenrod from unfair attacks by sneezy, watery-eyed, congested people looking for something to blame for their discomfort.

Poor goldenrod; for a showy native wildflower (actually numerous species of wildflower), it sure has public relations issues.  Some species, particularly Canada goldenrod, tend to act pretty weedy – showing up quickly and abundantly in abandoned cropfields and chronically overgrazed pastures.  In some cases, it can look much like an invasive plant, causing some (including me) to wonder about whether it warrants some control efforts.

Canada goldenrod (Solidago canadensis). A very pretty flower with a spotty reputation.

Canada goldenrod (Solidago canadensis). A very pretty flower with a checkered reputation.

But it’s during allergy season that goldenrod’s reputation takes the biggest hit.  When people start to sneeze and wheeze in the late summer/early fall, they look around (through their red puffy eyes) for the culprit, and goldenrod is the tallest, showiest, weediest looking plant they see.  Ah ha!  That must be the problem plant!

Well, actually…

Allergic reactions to pollen are usually the result of breathing air that contains pollen grains.  Our bodies react to the chemicals in those pollen grains, causing symptoms that include sneezing, itchy and watery eyes, congestion, and others.  The pollen we breathe in comes from plant species that rely on the wind to transport their lightweight pollen from flower to flower.  Those wind-pollinated species make a tremendous amount of pollen to increase the chance that at least some of their pollen grains will get blown toward other plants of the same species.

Grasses, including indiangrass (Sorghastrum nutans) don't have showy flowers because they don't need to attract insects to carry their pollen. The wind does the job instead.

Grasses, including indiangrass (Sorghastrum nutans) don’t have showy flowers because they don’t need to attract insects to carry their pollen. The wind does the job instead.

In contrast to wind-pollinated plants, plants that are insect pollinated tend to create heavier, stickier, pollen grains that don’t get picked up by the wind.  Instead, those plants rely on bees and other insects to carry pollen from flower to flower.  To attract pollinators, insect-pollinated plants have to create big, showy, and colorful flowers.  Wind-pollinated plants such as grasses, pine trees, and ragweed don’t need to spend resources making big fancy flowers.  They just make lots of pollen and let it blow.

Now, consider goldenrod flowers.  Definitely showy and colorful, right?  That, and the numerous insects crawling around on the flowers make it pretty obvious that goldenrod is insect pollinated.  When you walk through a patch of blooming goldenrod, you’ll never see a big poof of pollen come off the flowers as you knock into them.  Instead the pollen sits tightly on the numerous little flowers, waiting to stick to a fuzzy bee or other insect.

A bumblebee gathering pollen from stiff goldenrod (Solidago rigidus) in a restored prairie near Sutton, Nebraska.

A bumblebee gathering pollen from stiff goldenrod (Solidago rigidus) in a restored prairie near Sutton, Nebraska.

When you look at the evidence, it seems obvious that goldenrod isn’t to blame for our itchy watery eyes and congested noses.  How, then, did it become such a hayfever scapegoat?

I think of goldenrod as the kid in class who’s generally a good student, but always dresses a little too flashy and laughs a little too loud.  Ragweed, on the other hand, is like the plain-dressed quiet kid who throws spitballs at the teacher when her back is turned.  When the teacher whips around to see who’s responsible for the spitball in her hair, who do you think she’s going to blame?  The loud kid who’s laughing uproariously, or the quiet kid pretending to read his lesson?

Exactly.

Poor goldenrod…

Western ragweed (Ambrosia psilostachya) has tiny non-descript flowers, but produces LOTS of pollen, which is released into the wind for transport.

Western ragweed (Ambrosia psilostachya) has tiny non-descript flowers, but produces LOTS of pollen, which is released into the wind for transport.  Ragweed species are a major contibutor to seasonal allergy attacks.

Well, now that you are in the know, maybe you can help me restore the good name of this much-slandered native plant.  Just think of the popularity you’ll gain when you walk up to your puffy-eyed friends and explain to them (between their sneezing attacks) the ecology of wind and insect-pollinated plants!  To really drive the point home, maybe you should grab a bouquet of goldenrod flowers and shake them in your friend’s face to prove that no pollen comes out.

Just be sure to check for bees first.

The Softer Side of Wasps

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A couple weeks ago, I posted a photo of a wasp (along with some other shots from a walk through one of our wetlands) and mentioned that I’d have a story about that wasp in an upcoming post.  Here you go…

As I was looking for something interesting to photograph on my wetland walk, I noticed this paper wasp (Polistes fuscatus) nectaring on swamp milkweed (Asclepias incarnata).  It was moving slowly enough – and was focused so strongly on nectar – that it was relatively easy to get some photos of it.  In fact, I ended up watching and photographing it for about 10 minutes.

A paper wasp (Polistes fuscatus) feeding on milkweed nectar.

A male paper wasp (Polistes fuscatus) feeding on milkweed nectar.

You may or may not know that most (all?) wasps in our prairies feed on nectar as adults, but feed invertebrates to their offspring.  Many wasps are parasitoids – they capture and paralyze their prey, stuff it into a burrow or other similar structure, and then lay an egg on it.  When the egg hatches, the wasp larva feeds on the paralyzed invertebrate.  Most wasp species specialize in capturing a particular kind of invertebrate; some attack spiders, others go after cicadas, bees, flies, etc.  Parasitoid wasps tend not to be aggressive toward humans, and are (at least most of them?) solitary – just a single female provisioning food for her nest.  The mud dauber is an example of a parasitoid that is often seen in yards.  Their mud tubes often show up on the sides of houses or inside garages.

A mud dauber wasp creates a ball of mud to build her nest.

A black and yellow mud dauber wasp creates a ball of mud she’ll use to build her nest – a mud tube – which she’ll then fill with paralyzed spiders and her eggs.  A second species of mud dauber (irridescent blue/black) doesn’t make her own nest, but instead opens up the mud tubes of the black and yellow dauber, takes out the original eggs, and replaces them with her own!

The paper wasp is a little different.  Paper wasps are social, and their familiar hanging nests are initiated each spring by a fertilized queen.  Often, the queen will be joined by other females who help build the nest and feed the young.  However, any eggs laid by those other females are eaten by the queen, ensuring her dominance.  As the nest grows, multiple generations of wasps are produced, some of which become aggressive defenders of the nest – and that’s when the trouble starts for those of us who host paper wasps on our front porches.

Another difference between paper wasps and parasitoid wasps is that paper wasps catch and kill their prey (often caterpillars) rather than just paralyzing it.  In fact, after they kill a caterpillar, they’ll feed chunks of it to their older larvae and then give prechewed pieces to younger larvae.  You can read much more about paper wasps at this wonderful site from the University of Michigan.  In addition, here is a link to a short YouTube video with fantastic footage of paper wasps.

Returning to the wasp I was photographing in our wetland…

As I watched the wasp, I noticed that his feet were starting to accumulate quite a few sticky pollinia from the milkweed flowers.  Some of you who have been reading this blog for a while might remember a previous post that detailed the unlikely, but fascinating process of milkweed pollination.  Essentially, the process relies on an insect accidentally sticking its foot into one flower, pulling out a pollinia (a sticky packet of pollen), and then stepping into another flower and losing the pollinia as it pulls its foot back out.  Everything has to work just right for pollination to occur, and it seems as if it would hardly ever work, but the number of milkweed pods each fall are evidence to the contrary…

The same wasp a few minutes later, with multiple pollinia attached to its feet.

The same wasp as above, with multiple pollinia attached to its feet.  The pollinia are the yellow globs at the tips of its legs.

After the wasp accumulated a number of pollinia, it stopped feeding and started trying to remove the pollinia by running its legs through its mouth.  I couldn’t tell if it was eating the pollinia or just removing them.  Either way, it worked at it for quite a while, and it still didn’t get them all of (a good thing for the milkweed plant!)

The wasp trying to remove the pollinia from its feet (to eat? because they're irritating? I don't know...)

The wasp trying to remove the pollinia from its feet (to eat? because they’re irritating? I don’t know…)

Wasps are common visitors to flowers, but in many cases are less effective pollinators than fuzzy bees that get coated with pollen. However, as I’ve been paying particular attention to bees and other pollinators during the last several weeks, I have seen numerous wasp species on milkweed flowers.  That probably works out pretty well for the milkweeds, since all they really need is a creature that steps into multiple flowers as it crawls around.

Paper wasps are not among most people’s favorite insects, and for good reason.  Many of us have been stung by the aggressive defenders of a paper wasp nest.  On the other hand, those stinging wasps are just defending their nest and queen – a noble and virtuous act, and something that’s hard to blame them too much for.  Regardless, it’s also nice to see a paper wasp doing something that contributes to the greater good, like pollinating a milkweed plant.  When I’m out taking photos of fluffy white milkweed seeds later this fall, I’ll be sure to mentally thank the paper wasp for a job well done.