November 4, 2012

Botanical Hitchhikers

Those of us who grew up roaming woods and meadows can remember often coming home with a variety of hitchhiking seeds attached to our clothing:



Kids that I hung around with called all of them "burs" but we had no idea what the parent plants looked like, since we didn't realize that they had hooked on to us till we were far away and had started picking them off, preferably before going into the house. 

That, of course, served the plants' interests extremely well, since our actions helped to spread their range, avoiding competition with the parent and other plants in their immediate area.

Recently I've started to learn to identify more plants and in the process have found out, in some cases for the first time, where some of these "burs" come from.

At the top of the sock are the hooked burdock burs which are supposedly the inspiration for Velcro®. Each bur contains the small seeds shown in the lower right: 

There are several species of burdock, all native to the old world and widely distributed. The plant's enormous leaves make it nearly unmistakable:



Here is a picture of burdock in bloom:


Next are some of the most common burs, from a plant called agrimony (accent on the second syllable) or groovebur. 



There are 7 species of agrimony that are native to North America and the plant is reported to have a variety of medicinal uses. A member of the rose family, it has small yellow flowers and compound leaves. Here is a picture of the plant showing the flower stalk bearing the burs after blooming:


Here is a close-up view, and notice how the burs are angled down, the better to snag on a passing mammal: 


Next is cocklebur, a member of the aster family.


It is found mostly along streams and in wet areas. Each football-shaped cocklebur fruit contains two seeds. 


It has large coarse leaves like burdock, but in general the plant is much smaller.

Last but not least are the seeds of beggarticks or sticktights.


These come from plants in the genus Bidens and have a wide variety of common names. There are about 200 species of Bidens, and they occur all over the world. Some common members of the genus are not at all showy, with no petals or ray flowers:


Another one in this area is the very showy Nodding Bur Marigold, generally a plant of wet areas:


If you have ever had to cut any of these burs out of your dog's hair or tried to pick one out of your carpet you can really appreciate their tenacity. Plants whose seeds stick to clothing, fur or feathers are termed zoochorous and they have managed to exploit this characteristic to spread all over the world. 

A few posts back I wrote about the huge Pleistocene mammals that roamed Ohio just 13,000 years ago, and postulated that they probably had lice and fleas. Just think about what else they were carrying around in all that fur!





2 comments:

  1. I remember acquiring all manner of burs at Girl Scout camp Happy Hollow in west central Ohio. I never learned anything about all those annoying hitchikers until now. Thank you! Very interesting!

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  2. Loved your sock illustration. :)

    Deb

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