Have seeds, will travel

By Steve Roark | The Winchester Sun

Plant life is absolute­ly lush in our part of the world. If the ground is not paved or has a build­ing on it, it usu­al­ly has plants grow­ing on it or at least try­ing to get a toe hold. Which begs the ques­tion: how
do plants spread if they are lit­er­al­ly root­ed to the ground? The answer is in seed design, and sev­er­al inge­nious mech­a­nisms are used to allow plant embryos (seeds) to move away from the shad­ows of the moth­er plant. 

Seed dis­per­sal can be rough­ly divid­ed into sev­er­al broad cat­e­gories: wind, ani­mal, pro­pelled, and dropped. Wind is known to all who have picked up a mature dan­de­lion seed head and blown on it to watch the lit­tle para­chutes (each with a seed pas­sen­ger) float off on the wind. There are lots of plants that use wind for seed trans­porta­tion. Milkweeds and this­tle also use the para­chute tech­nique, and sev­er­al use a sin­gle wing that spins around like a heli­copter, used by maples, yel­low poplar, and ash. There are many oth­er wind-borne seeds around.

Animal trans­port­ed seeds fall into two cat­e­gories: the cling­ing types are the sticky ones that attach them­selves to fur or cloth­ing. Many of you have cursed seeds like beg­gar lice, stick-tights, seed ticks,
cock­le­bur, and oth­ers that cov­er your pant legs when walk­ing in weedy places. The oth­er ani­mal trans­port mech­a­nism is bribery. The plant pro­duces a tasty fruit to entice an ani­mal to eat it. The enclosed seed pass­es through the gut unharmed and is pooped out some­where away from the moth­er plant with fer­til­iz­er to boot. 

Propelled is where the seed has a mech­a­nism that phys­i­cal­ly throws it away from the moth­er plant. Touch me-nots are a good exam­ple, hav­ing seed pods that are spring loaded, and when mature will explode and throw the seeds all over the place. Witch-hazel, wis­te­ria, and win­ter-cress all use this method.

I’ve seen grav­i­ty list­ed as a seed trans port mech­a­nism, and heavy round seeds like acorns, hick­o­ry nuts, and wal­nuts could drop off the tree and roll down the hill. But with most of our nut seeds, anoth­er ani­mal trans porter more like­ly comes into play. The squir­rel, and to some extent blue jays, eat­ing many nuts but also stock­pile them for win­ter use, hid­ing them in the ground in var­i­ous places. Thankfully, they don’t remem­ber them all, and some get to sprout and grow a new tree some dis­tance away from the moth­er tree.

Observe seeds out in the wild and see if you can fig­ure out the trans­porta­tion method they use. They are fur­ther proof that nature does all things with a purpose.