So many interesting answers to Friday’s puzzle – thanks to all of you for putting out the effort! It most certainly is an abiotic problem – but was it temperature, suggested by Deb? Water, suggested by Foy, Gayle and Ed? Light, suggested by Nancy? My plan was to have an extensive soil test run to address the possibility of pollution (suggested by Jim, Heather and Paul), except we discovered the source of the problem last summer when we finished digging our pond:
As you can see in this photo, we have solid clay about 12″ below the surface. (And I do mean solid. I’ve kept lumps of the stuff to take to seminars, so when people say “I have clay soil” I pull this out and ask if this is what they mean. Usually not.)
So in this area of our yard we have a perched water table: the water percolates through the topsoil, hits the clay, and spreads horizontally. When we had turf in place, it tended to keep the upper few inches relatively dry, which allowed the dogwood roots to survive. When we took out the turf and covered it with wood chips (to conserve water!), the soil became saturated nearly year round. We dug out the tree a few weeks ago, and this is all that remains of the root system; the rest of the major roots had rotted away:
We’ve replanted the tree in another area of the yard with much better drainage, and we’ll keep track of its establishment and leaf size. I think it will recover, as new roots will emerge from the main root mass.
(Paul, thanks for the kudos on the fence design! My husband built this, and he’ll be pleased to see your comment.)