My Mom (1935) and Dad (1929) were born on the same date, six years apart. Shortly after moving into their Tennessee home in 1964, Dad dug a small oak seedling up from somewhere on the property and planted it in the new construction debris that made up our front yard (Despite the impoverished site, it became a majestic tree; until a truck rumbled through a few years ago and cut it in half lengthwise to keep it out of the power lines. But hope springs eternal — as we shall see). Upon Dad’s passing in 2000, Mom put a small plaque on the tree and sprinkled his ashes around. Apart from beauty and shade, the tree was now . . . important. With this newly christened treasure, I set about to preserve it for all time.
So how does one immortalize an oak tree? Why, collect the acorns, of course. Plant ’em. Help ’em grow.
So I did. The result is three young trees in Ankeny, IA , the largest of which is a strapping thirty-foot teenager. Despite its Tennessee provenance it has thrived through Iowa’s extreme winters with no trouble at all. Dad would be proud.
As we proceed further into a changing climate, these offspring oaks, in Iowa ground and of Tennessee provenance, may have more to give. Iowa may become progressively more like Tennessee. Some plant species adapted to Iowa’s past and current climate will struggle or fade away. Indeed, the very notion of “native” species will be turned on its head: what does “native” mean when the “native” environment is repeatedly swept away on timescales of a single human lifespan? The assumption (by some) that “native” plants and plant communities are always the most suitable for urban and home landscapes becomes more uncertain.
“Resilient” and “functional” will come to more accurately describe plant specimens, species, and communities that are most suitable for a rapidly changing climate. And the clearest path to resilience is diversity. The notion of planning and planting diverse tree communities for resilience to change has precedent. In reaction to the devastating effects of diseases and pests that destroyed virtually every American elm and American chestnut (and other species), a rule of thumb called the 10/20/30 rule has long been suggested: no more than 10% of plantings should be within a single species, no more than 20% within a single genus; and no more than 30% within a single family. The risk of a disease or pest wiping out every tree is greatly reduced.
To hedge against the new “pest” of climate change perhaps we can sprinkle a mindfulness of provenance into our genetically diverse plantings. That is, (in the Northern Hemisphere) let’s deliberately move some plants from South to North. So, my oak tree may indeed have more to give. And maybe my bald cypress, which seems to thrive as well on a well-drained Iowa hillside as in a Louisiana swamp. Or my Osage Orange, ‘White Shield,’ plucked from arid western Oklahoma, but from a species which achieves its highest densities in repeatedly flooded “bodark swamps.”
I’m looking for more. Mindful of provenance. Plant Resilient.
July 21st, 2015