About a couple of years ago, a volunteer plant started growing next to the back fence line, inside the retaining wall. By the time I noticed it, it was looking interesting so I let it grow, pruning it occasionally so it grows flat against the fence, not quite an espalier, more two-dimensional for privacy screening between the two yards.

I suspected it to be a Chinese Pistache (Pistacia chinensis), a common landscape tree that requires little to no water and is resistant to oak root fungus. It has good fall color that turns luminous orange to red (sometimes a shade of yellow). The summer leaves sure look like it.

Unfortunately, I don't recall what it looks like in the fall, nor could I find pictures of it in the fall.

I decided to do some research online. I used various websites,

The Arbor Day Foundation -  https://www.arborday.org/trees/whatTree/;

The Sacramento Tree Foundation - https://www.sactree.com/pages/251 and a host of others. But none of them identify my tree as a Chinese Pistache, even though the plant is in their database.

I recall my brother showing me a free app that does plant identification. It's called “Picture This.” I downloaded the app and started taking pictures around my garden to test the app.

I tested it on 12 plants. It accurately identified 8 plants, there were 2 plants that were within the same plant family. I have tree collard and it identified it as a cabbage. My holy basil is supposed to be sweet basil. It incorrectly identified the Tagetes lemonii as a Chaste tree (Vitex agnus-castus) without the yellow flowers, maybe it could not tell the difference.

Last, but not least, the app says I have a California black walnut (Juglans californica), which requires no irrigation and is resistant to oak root fungus. I'm disappointed that I was wrong about its identity, but excited at the same time because it works perfectly with my food forest garden.

For now, I will let the plant keep growing and “reveal” itself. If it is a Chinese Pistache, I will get nice foliage color in the fall. If it's a California black walnut, I will eventually get walnuts from it.

Either way, it's good.

As for the app, I'll have to play with it some more, it's a nice and fun app to have, but I wouldn't rely on it as a primary tool, especially for people with a lot of “specialty” (or obscure) plants.