A bit more about cultivars

I should probably qualify my last remarks, because there are undoubtedly some mid-Westerners getting a bit hot under the collar right now. What I think it is important to add is ‘especially at the northern fringe of the species range’, i.e. where I am, where graft unions are very prone to winter damage, ultimately leaving one with an expensive tree growing from the rootstock (which, by the way, will have been a common black walnut seedling grown from a nut, sacrificed for the greater good of the scion). This, also by the way, is the Third Law of Nut Production: Rootstocks Make Very Expensive Nut Trees. The following are the First and Second Laws: Use Selected and Named Varieties, and, Grafted Trees Don’t Like Marginal Conditions. If you read them in order, there is a modicum of sense to them. So, no matter how good your soils are, if you live in the same climate zone as we do, you can take the conditions as marginal.

Now let’s address the energetics of nut production. A grafted tree will produce nuts at a very young age, because it grows from a scion which is already mature wood. A common black walnut will take some years to reach physiological maturity, and the only way to speed that up is to create the best growing conditions possible so that the tree grows as fast as it can. Still you will not know when to expect nutting, but my goal is to minimize this period (more on this later). But we must still deal with the issue of the tree’s ability to fill all those nuts it is going to produce, which will be related to the canopy size for the number of nutting sites within it. A young grafted tree will still not produce an ‘economic’ yield, because it will be too small to do so. Pushing a tree to nut at an early age creates the risk that too much energy will go into multiple shell production, leaving insufficient resources for the kernels to fill them. Cumulative solar energy incident on the canopy declines with increasing latitude, so, once again, there is a risk that a tree genetically driven to produce large quantities of nuts, will, at our latitude, leave those shells empty. The tree’s root system grows in tandem with its above-ground structure. Resource capture by the roots is also important here, as the tree requires nutrients to produce fruit. Small root systems will not sustain heavy nut loads.

So, all in all, my original post was fair even if it wasn’t fully explanatory. Just remember the three Laws of Nut Production, and make your choice.