how do you know it's not juglans californica? what are the keys to tell them apart?
Juglans californica only grows in southern California, and is a large shrub or small tree. This was a large tree. I'm not sure if J. californica even could survive in Davis, so far from its native range. However... part of your confusion may lie in taxonomy, hindsii used to be a subspecies of californica: http://www.calflora.org/cgi-bin/species_query.cgi?where-taxon=Juglans+californica+var.+hindsii so if you are using an older reference they may show as the same.
you can also use leaf shape and hairs to distinguish: http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?key=9146 .
i do remember seeing a lot of giant walnut tree in sacramento, bc of the huge size, and height, we can assume its juglans hindsii, but what if it is a younger tree? what if some one purposely planted it there. There have to be useful keys to help identify the specie. I know jepson manual have some describtion on the leaves to help differentiate the northern and southern species, but if you look on calflora, their pictures is all over the place, they have what look like acute, and some acuminate under juglans hindsii, the same goes for their pictures of juglans californica.
so basictly we're only using size, and location to identify a specie, which i do not agree is a good way to identify any species at all. Someone could just bring some seeds to any locations. Though hind walnut is described to be more robust than california, and i hope thats true.
Well, it isn't ideal, but the fact is if we decided to identify every plant species in existence based only on global keys considering every species on the planet, most things would be very difficult to identify. I know you aren't proposing quite that... but it's just a balance. I've never, ever heard of a southern California walnut tree in northern California (though there may be hindsii planted around southern CA). On the other hand. people like you on iNaturalist might be the first one to find it. And you are right, if I were shown a sapling and was told it was either of the two species, I could probably not tell it apart. I will say thought that once they get a bit bigger J. californica is almost always multi stemmed and never looks like it will be a big tree.
In truth the issue probably isn't the lack of good keys... but instead that these species look almost identical except for size. That is probably why they used to be considered the same species. Maybe they still should be subspecies and should not have been split. Most likely if they shared a range they would also produce hybrids.
Good questions by the way! I don't really disagree with you, it's just that I don't know any other way to identify it when small. Very similar species, probably very recently diverged evolutionarily. There is also evidence that J. hindsii was grown extensively by Native Americans who possibly selected for its size and nut production, which would mean J. hindsii is not a entirely 'natural' species and instead one of the ones the Native Americans had in their vast areas of 'native ecosystem permaculture' but the same is true for many plants, probably, and that's another entirely fascinating discussion.
Anyhow, if you had tons of money and time you could use the genetic barcode to identify each species :)
lol, i'll leave it for the moment. I am moving on to the other species to id ^^
Here's to the day when genetic barcoding has become as affordable and ubiquitous as digital sounds and images have!
i will both love and hate that day. Trichorders!
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