BURDOCKS AND COCKLEBURS

      Seed dispersal is important to every species of plant that produces seeds.  Many, like dandelions and milkweeds have small seeds on "parachutes" that float away on the wind.  Seeds in berries pass through birds' digestive tracts and are passed later.  And prickly seed pods hitch rides on mammal fur.  Plant species that have their seeds spread into proper habitats, far and wide, and away from parent plants, have a good chance of thriving, as a species, indefinitely.  

     Common burdocks and common cockleburs have burs in their names, and for good reason.  These  plants have characteristics in common, particularly in how their seeds are dispersed over the countryside and away from the parent plants.  Burdocks and cockleburs have bristly seed capsules that, not only protect the seeds inside them until they mature, but those pods break off and hitch rides in the fur of mammals, including foxes, rabbits, deer, chucks and others that pass by these plants during autumn.  Those mammals become irritated by those thorny seed capsules in their fur and stop to pull them out with their claws and teeth, often away from the parent plants.  Eventually those seed protectors decay and their seeds fall out onto the ground, where some of them sprout the next spring, if not eaten by mice and small, seed-eating birds through fall and winter.    

     Burdocks and cockleburs, or clotburs, have other traits in common that help make them interesting.  They both flourish in moist pastures, waste ground and roadsides, all sunny habitats, where soil had been disturbed, through much of the United States.  Both kinds bloom from July to October.  Both often have burs in clumps.    

     Aliens from Europe, common burdocks have a two-year cycle.  Their first year of life they have a rosette of small leaves close to the ground.  But during their second, and final, year they are about five feet tall, have large leaves near the ground and are bushy.  Each plant has several pinkish-lavender flowers, which are pollinated by bees, butterflies and other kinds of insects, which add to this plant's intrigue.  And painted lady butterfly caterpillars eat the foliage of these plants.  Their seeds form in rounded, green capsules that later turn light-brown and bristly.

     Common cockleburs are native, annual plants that grow only a couple of feet tall.  Their one-inch seed pods are oval and very bristly, each one with innumerable strong, sharp spines that are the shape of tiny fish hooks.  Those seed capsules are green in summer, but turn brown in fall.  And each pod has two seeds in it.           

     The bristly seed pods of these plants that stick to the fur of mammals for seed dispersal is the most outstanding trait they share.  Seed dispersal is important to plants because they can't get around on their own.  And the method of seed dispersal in these plants is interesting to experience.      

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