California Tree Identification: Urban Tree Key

Urban Tree Key is a useful resource for identifying commonly encountered trees in the state of California. The best part is that you don't need to be an expert or even vaguely familiar with dendrological vocabulary to use it. The photo examples for each characteristic make it easy to navigate.

I'm a long way from California and couldn't use the Urban Key Tree in the practical sense. I also wanted to determine the site's accuracy, so I decided to keep a particular species in mind when I got started to see if the app would lead me to it. Here was my experience.

Blue Gum (Eucalyptus globulus)

I selected the option for leaves and it gave me two choices: tiny leaves or normal sized. Of course, size is purely relative. The great thing about the photo feature is that it can help nudge you in the right direction. For instance, the leaves of a coast live oak are much smaller than those of a maple, but they would still be considered normal sized when compared to the "tiny leaves" in the image the site provides.

Once I selected "normal sized" I was given a choice between compound and simple. If you're not already familiar with the classification of leaves, this is a good way to learn. Selecting simple gave me three more options:

After comparing to my initial photos, I went with alternate. This gave me two more choices: "Leaf edges completely smooth, without teeth or lobes" OR "Leaf edges are toothed, spiny, scalloped, or lobed". I chose the former and was given four more choices (the fourth was titled "All Others"): 

This is where things got tricky, as I could only distinguish so much from my initial images. I couldn't smell the leaves or hold them up to the light. If I didn't already know the species and had been using this app as intended (out in the field), I would have been able to conduct a physical examination and would have ultimately selected the third option. 

Doing so gave me two more choices: "leaves are lighter green on the underside" OR "leaves are the same color on both sides". The color appeared relatively uniform in my pictures, so I went with option two. This led me to tree bark (rough or smooth) and I went with smooth. The next options were for leaf length: greater or less than 6". The leaves appear quite long in my initial photos, so I picked the first option. Believe it or not, the site took me straight to the Blue Gum tree!

It didn't end there. Clicking "Select Tree" routed me to the Urban Forest Ecosystems Institute site. It gave me loads of general information like common names, specific tree characteristics, tree site conditions and constraints, pests and disease information, and health and safety concerns. It also provides an interactive location map. 

The Urban Key Tree is made possible through a partnership between Cal Poly Urban Forest Ecosystems Institute, the California Department of Forestry and Fire Protection, and Urban Ecos. It's easy to use, informative, and although I used it on a desktop, it's mobile friendly. The only limitations of this app that I can discern are that certain options are seasonal. In fact, starting with leaves would make it tough to determine a deciduous species if you're out in the winter months. This could possibly be overcome by examining leaf litter, but could still be limiting in terms of color and scent. Also, some of the options are related to each species' flowers which obviously are not present year-round. Despite those drawbacks, the Urban Tree Key is a solid resource for species identification in California.

Resource Link: https://selectree.calpoly.edu