Seeds of Change
Today John and George were so busy putting the finishing touches on our upcoming Native Plants MOOC (yea, it’ll be mobbed). We didn’t take much field time, except to look at something you see every day but ponder once a decade—native woody plants coming up seemingly isolated where you don’t expect to see them.
That led to some thought on why plants wind up growing where they do. Oh, I know the answer! The wind, or a bird, or a bear in the woods drop a seed, and the seed grows. Got it, but events aplenty happen between the bird ingesting the seed and a tree grows in Brooklyn. Nature does not work in a human time and space.
For starters, that seed had to arrive from somewhere. Maybe merely across the creek, or then again, perhaps from across the sea. There are plenty of transoceanic examples, and the Bottle Gourd stands out. The species has an archaeological history widespread in the Americas dating back 10,000 years and in Asia almost that long. Botanists have debated for decades how this species could seem to be native around the ancient world so long ago. It did not originate twice, on both sides of the Pacific. Did very very ancient people move it thousands of miles? One notion is that Easter Islanders took it westward to the Old World. Another idea is that the first Native Americans brought it from Asia. Or maybe it floated a few thousand miles. To test the bobber theory, researchers floated some for about a year in sea water, and let them sit another six years; the seeds sprouted like new. Take home lesson: seeds get around.
So then, the seeds arrived from somewhere near or far, and now they can grow. Hold on, not so fast. How long a delay between arrival and growth? Maybe the season is not right this month. Maybe conditions aren’t right this century. How about another thousand years? Seeds can be patient, and can await environmental cues, such as disinterrment. In 1879 Professor William Beal at Michigan State University buried in glass jars seeds of several wild species, leaving a time capsule experiment that remains running. The seeds are tested at intervals, and some remain willing despite attrition. Going back farther, barley seeds from King Tut’s tomb reportedly sprouted in modern times, although the claim is disputed.
Free of dispute, Canna seeds 600 years old from an Argentinian grave spawned pretty new Cannas. And their circumstances were weird. The Canna seeds from the grave were inside walnuts. Ancient biotechnicians understood how to insert Canna seeds into immature living walnuts, allowing the nuts to mature into rattles. In 2012 30,000-year-old seeds of a Carnation relative buried (by squirrels) in Russia grew like Rip Van Winkle awakening. That’s probably the all-time seed nap record.
Right, so the seeds came from places unknown, then they waited patiently in the soil seed bank. Now it is time to boogie! The seed sprouts dutifully, and hello world! Hello drought, hello shade, hello sun, hello frost, hello competition, hello drowning, hello bugs, hello fungi, hello hungry bunnies. The perils facing a tender green sprout remind me of leaving home at age 18!
Obviously the conditions must be suitable—that goes without saying doesn’t it? Probably, but even that boring observation gains interest if the seedling’s establishment requires relationships with other species. (We’ll come back to this next week.) It also becomes more interesting if the overall conditions are changing…oh for example, let’s say by Global Warming. Just this year the Sunshine State figured in an eye-opening example. In the Proceedings of the National Academy of Science, January 2014, biologist Kyle Cavanaugh and collaborators applied 28 years of satellite imagery to discern, as they say in their own title, “poleward expansion of mangroves is a threshold response to decreased frequency of extreme cold events.” Where a mangrove might sprout has shifted in just 28 years. That’s not my lifetime, but that of my son.
Today we looked at a lonesome Gumbo Limbo sapling with its secret history, a single Pineland Pinweed 10 miles from any known others, and where did that baby Hercules Club come from? A little imagination beyond “bird dropping” makes it more fun. Maybe the guilty birds were the last flock of Carolina Parakeets in 1920. Who can say it ain’t so?