How burs disperse seeds in fall

 
Posted10/27/2017 11:26 AM
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  • Woe is the naturalist who gets burdock in her hair.

    Woe is the naturalist who gets burdock in her hair. Courtesy of Valerie Blaine

  • In fall, burdock burs are menacing for passers-by.

    In fall, burdock burs are menacing for passers-by. Courtesy of Valerie Blaine

  • Burdock burs persist in to winter. Their hooks always ready to grab jackets, mittens and dog fur.

    Burdock burs persist in to winter. Their hooks always ready to grab jackets, mittens and dog fur. Courtesy of Valerie Blaine

  • Enchanter's nightshade uses the familiar hook and loop method of hitchhiking.

    Enchanter's nightshade uses the familiar hook and loop method of hitchhiking. Courtesy of Valerie Blaine

Picked up any hitchhikers lately? Chances are you've picked up more than a few if you've walked in the woods recently.

The hitchhikers in question are seeds -- or burs -- and there are lots of them looking for a ride into the next season.

Technically, burs are the fruit that contains the seed. There's an amazing array of designs for burs, as plants have evolved all kinds of different ways of catching rides.

What they have in common is that they're prickly and tenacious and irritating as all get-out.

Once they grab on to jeans, socks, sweatshirts, or fur they will not let go. They defiantly dig in deeper when you try to remove them.

They're the bane of anyone who walks with a longhair dog in the woods.

Burs are a big bother for us, but from a plant's point of view, the hitchhiker method of seed dispersal is brilliant.

It gets the job done. Seeds get a free ride from the parent plant to new fields and prairies and woods.

Eventually, the animal who has been carting a bur around rubs against a tree or wallows on the ground, and the bur releases the seed. A new home for a new plant.

Burdock, cocklebur

High on the list of plants with nasty burs is burdock.

This is a plant you don't want to run into.

Or, for that matter, you don't want to even brush lightly against it.

Burdock is a tall weed in the sunflower family. It grows throughout the United States, popping up in old fields, along the edges of woods and parking lots and other disturbed areas.

Its flowers are pretty, deep purple clusters that attract lots of pollinators in the summer. But from the flowers come the troublesome fruit. Round and green at first, the fruit turns brown come fall. Each one is a ball of wicked little hooks that are just waiting for some hapless mammal (like you) to walk by.

The hooks seem to jump out to catch on sleeves, jackets, fur -- and, if you're really unlucky, your hair.

It's close to impossible to extract burdock burs. The more you struggle with a bur, the deeper it digs in.

To extricate burdock from our English Springer's fur, I've had to apply oil and hair conditioner -- only to resort to scissors and a hair cut in the end.

Cocklebur is right up there with burdock on the list of worst-seeds-ever. In fact, they're relatives in the sunflower family and have similar flowers.

The prickly bracts of cocklebur flowers foreshadow the nettlesome fruit that is to come. The fruit is hard, woody, and well-armed -- the better to catch you with. Cockleburs readily entwine themselves in fur and work themselves into clothes.

As bothersome as they are, burdock and cocklebur have a plus side.

In the late 1940s, a Swiss engineer named George de Mestral was out walking his dog when both he and his canine got covered in burs. (There's some debate whether these were burdock or cockleburs.)

When Monsieur de Mestral got home, he tugged out the burs and put one on a piece of fabric.

Examining this under a microscope, de Mestral discovered the myriad hooks on each bur. He observed how each hook caught on to a loop of fabric.

This was his "ah-ha!" moment. De Mestral took the design to a textile manufacturer in France and voilà! Velcro was born. (Velour + crochet = Velcro.)

Beggars-ticks

Another notorious hitchhiker has a slightly different design.

Beggar's-ticks, or as some people call them, devil's beggar's-ticks, are plants with few fans. There are a few species of beggar's-ticks in Illinois, all in the sunflower family.

The flower turns into an arsenal of sharp, two-pronged seeds with a nasty habit of catching onto clothes. Like daggers, the prongs can poke right through most fabrics -- and they hurt.

Enchanter's nightshade and stick-tight

The sunflower family is not the only plant family with bur-bearing species. The primrose family contains a lovely little wildflower called enchanter's nightshade.

It's not such an enchanting plant when those flowers turn into spiny little balls. These are the dickens to remove from clothes.

Putting bur-ridden clothes in the washing machine and dryer only makes them worse.

I've had to throw out T-shirts that just weren't worth the time to de-bur.

The rose family also produces some aggravating bur-bearing plants.

Agrimony is a common wildflower with attractive, small yellow blossoms in summer. Unfortunately, these morph into small, bristly fruit.

Let's not forget stick-tight, in the forget-me-not family.

Stick-tights (also called stick seed or Hackelia virginiana) have summer blossoms lined up in an elegant arrangement on a stalk. Don't let their beauty fool you -- come fall, the resulting burs will inflict torture.

These tiny barbed fruits will eat up your clothes and ruin your dog's coat.

Should you get them in your hair, you might as well get the razor out and shave your head.

Does this mean that bur-bearing plants are bad? Not at all. They're doing their thing -- and quite well, at that.

Every plant mentioned has been used for either medicinal or nutritional purposes by indigenous people, early settlers and herbalists.

Hitchhikers are an occupational hazard for those of us who like to wander in the woods, but it shouldn't keep us indoors. There's a certain Zen of sitting in an easy chair after a long day in the field, plucking seeds out of your socks or de-burring your dog.

Burs are a small price to pay for enjoying the splendor of the autumn woods.

• Valerie Blaine is the nature programs manager for the Forest Preserve District of Kane County. You may reach her at blainevalerie@kaneforest.com.

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