Those good seed trees

Rod Croskery (he of the only site currently on my blogroll) wrote to me recently posing a question that I suspect many would like to ask:

[About the tree in Westport] planted in 1937 by Dr. Ford Goodfellow, the parent tree has very little trunk but an enormous canopy. [The owner] assures me that it has borne heavily every year for the last twenty. If the nuts are well-filled, the parent might meet your criteria for a good orchard tree.

This is a bit of a challenge, because it is growing in a site distinct from the farm. I responded to Rod that currently I was only interested in selecting from the population that I had on the farm. Many rural Ontario communities have populations of black walnut trees, many of which (I am separately informed) would be descendents of the original parent stock brought up by United Empire Loyalists a couple of hundred years ago. This ignores the other common knowledge that First Nations’ peoples also spread the black walnut eastwards from southern Ontario.

These populations I have observed to be regularly productive, so here is my suspicion: that the environment in many of these communities reduces the risk of early spring frost damage to the trees’ flowering, mainly, I believe, through low-level mixing of exhaust gases from heating systems. Most of these trees are within or just moderately above the mean roof line of the community, where such effects could be expected.

How could we test this? If you have a potential seed tree in such a community that you are interested in, I suggest you hang a max-min thermometer on the trunk at breast height (1.35m) on the north side, inside some sort of shield to protect it from the elements, and compare the readings with Environment Canada’s values at the nearest observation site on those nights when spring frosts occur. Do the readings match or not? Remember to reset the thermometer daily.

Because my fields are frost prone, I believe my good seed trees must be relatively later flowering than the rest of the on-farm population. Alternatively, my non-seed bearers are too early for my site, something I must quantify this coming spring. More on this later.