The Problem with Counting Pawpaw Trees, in Utah or Anywhere

In August I got the idea that it would be possible to count all of the pawpaw trees in Utah. That idea set us on a course to visit the feeble BYU pawpaw orchard, a humbling experience because BYU owns so many more pawpaw trees than I do. But not completely humbling, because BYU's trees have been growing for about as long as mine have. And while the tallest of BYU's trees is about up to my knee, all my trees are about a foot taller than I am.

It wasn't more than a few days after we visited the BYU orchard that I notice the efforts that were being undertaken by the rootstock of the Wells cultivar. The rootstock, which is technically a different pawpaw tree than the Wells branches that it nourishes, decided to send up its own branches. And so, out of the mulch have grown two little "trees" (one of them bigger than most of the trees in the BYU orchard), native to the rootstock and genetically distinct from the Wells branches. 

And so, how to "count" the number of pawpaw trees in my own yard? On one hand, I might say that because they new sprouts come from the roots of the wells, they are still the same tree, genetically identical. That would work, except they're not genetically identical with the Wells branches. So, it would seem that there are two trees. To drive this home: Pawpaws are almost always self-incompatible (which means they can't cause themselves to bear fruit but they need a genetically distinct fellow pawpaw to do the job); and if I were to let the rootstock's new sprouts grow up and flower, their flowers would be able to fertilize the flowers of the Wells, and produce fruit. 

This leads to a second option for how to count pawpaw trees. This second option would be to count each grafted tree as two trees, given that its rootstock and its branches are genetically distinct. This would mean that I have seven pawpaw trees in my yard:

1. the rootstock that nourishes the Shenandoah branches

2. the Shenandoah branches

3. the rootstock that nourishes the Wells branches

4. the Well branches

5. the rootstock that nourishes the KSU-Atwood branches

6. the KSU-Atwood branches

7. the unimproved tree, whose rootstock didn't do a good enough job of nournishing the Sunflower cultivar branches (which died), and then the rootstock put up its own branches

This approach would work okay, but if I'm using as a litmus test the question of being genetically identical, then consider a scenario in which I were to have two Shenandoah cultivars and two KSU-Atwood cultivars growing in my yard. The two Shenandoahs would be the same tree (because they are genetically identical) and the two KSU-Atwoods would be the same tree (because they are also genetically identical). So that would be a total of four genetically distinct rootstocks and two genetically distinct branches, for a total of six trees (which isn't the eight trees I would have if I took the easier approach of counting each grafted tree (rootstock-branch combo) as two trees.

In some ways, then, the most accurate way to count all of the trees in Utah would be to count the number of rootstocks, and then to count the number of cultivars, and then add that number together. That would mean that if twenty-six people in Utah owned the Shenandoah cultivar, I would count twenty-six rootstocks but just one Shenadoah cultivar for a total of twenty-seven pawpaw trees. 

But none of this seems very intuitive, and all of it seems much more complicated than counting trees should be. And the definition of "tree" becomes more complicated that most people would be willing to tolerate. So what to do? 

For right now, just look at some pictures, below.

The larger of the two sprouts from the Wells cultivar's rootstock.

Another picture of the same sprout.

The smaller sprout

The biggest pawpaw on the Wells branches

The second biggest pawpaw on the Wells

The two smaller pawpaws on the Wells

Just in closing, I'll mention that the largest pawpaw on the Wells is starting to feel soft, so I imagine it won't be many more days before we have a very humble, but first annual, Utah Pawpaw Festival.