Hitching a Ride
In the late 1940s a Swiss engineer was taking a nature walk with his dog when he noticed cockleburs sticking to his pants. The engineer was curious about these "sticky seeds" and took a closer look at them using a microscope. He found something that gripped him: the burs were covered with hooks that stuck in the fibers of his clothes. He was fascinated by this finding, began experimenting and, a few years later, he patented a product called Velcro®.
Why would cockleburs go for a ride on a Swiss engineer? If we want to go somewhere, we have lots of choices. We can walk, bike or go by car. Plants, if you'll pardon the pun, are more rooted. When a plant needs to move it has to do so vegetatively, such as when strawberry plants send out runners, or go by seed. The movement of a seed from its parent to another place is called seed dispersal.
There are many different types of "sticky seeds" in Missouri, some of which are seeds and others that are actually fruits. Some common ones are beggars' ticks, Spanish needles, tick trefoil, cheatgrass, needlegrass, burdock and cocklebur. Seeds of broad-leaved plantain are about as small as the head of a pin, while the fruits of cockleburs can be as wide as a nickel. The fruits of burdock are shaped like a top and others, such as beggars' ticks' fruits, are long and flat.
Whatever their shape, fruit and seed hitchhikers have one thing in common: they all can latch onto passing animals, including you and me. Sometimes, the fruits seem to leap out and attach themselves. And how the hitchhikers attach themselves is another story. Some use hooks or barbs while others use sticky fluids.
You can find sticky fruits and seeds throughout Missouri, from the prairies of the southwest and north to the forests and glades of the Ozarks, maybe even in your own backyard. Some of the common ones are in a group of plants called tick trefoils. Tick trefoils belong to the same family as the garden pea and string bean and have small purple to white, pealike flowers.
Some tick trefoils sprawl across the ground, while others grow waist-high or taller. A whole tick trefoil fruit looks like a flattened string bean pod with a narrow waist between each seed. Tick trefoil fruits are covered with hooked hairs. They grow in many types of places