This is a tree that I have been growing. I'm wondering if this is a mulberry, and if so, what kind? Location is Arizona.
It is a mulberry. What isn't clear from the photos, and may not be clear without a DNA analysis, is whether it's a hybrid of the native red mulberry and the white mulberry imported from Asia in the hopes of starting a silk trade in North America (white mulberry is the main food source for silk caterpillars), or whether it's distinctly a red or white. The berries won't always indicate this, and the leaves won't always indicate this. At this point, our red mulberry has seen sufficient habitat loss that most new mulberry trees are hybrids.
I am sure it is a Mulberry (Morus sp.). I have two of them growing in my garden. The bark, leaves and flowers look exactly like my trees. Note that the Mulberry has different male and female flowers (and off course only the female produce fruit). To be 100% sure I looked it up in Blameys' "Mediterranean wild flowers".
Looking at the landscape in your area (which suggests somewhere between west Texas and southern Oregon) it might also be a black mulberry.
Here is a snippet on black mulberries