Riparian flora

The most visible tree growing along the creek margins is the cottonwood, of which there are two local species: (Populus fremontii) whose leave is heart shaped, wider than long, with a brillant yellowish green color; and (Populus angustifolia), with narrower leaves.

We can also see locally growing the ash tree (Fraxinus velutina). Today, this tree is more common in the municipality than the walnut (from which the municipality takes it's name). The ash has a rounded crown and extended branches. It has composite pinnate leaves, usually 5 to 9 pieces in pairs with the exception of the final one. The color of the folliage is brilliant green above, and paler below (Click on the image at the right, to see it better)

The willow (Salix gooddingii) grows along the banks of the creeks. It has a very narros and lanceolate leave (Click on the image at the left to see it better)

The Arizona sycamore (Platanus wrightii), is a large tree also growing along the creeks. It is very easy to identify, as it's bark has a camouflaged apearance, with rounded brown areas over a whitish bark. It's leaves are in the form of stars, divided in 3 or 5 (sometimes even 7) large lobes.

Also, along the Nogales creek, years ago there were many walnuts (Juglans major) from which the Municipality and the city inherited their names. First the indians, and later the ranchers, collected the nuts as food. We can still see some specimens in the canyons near Nogales. It has a pinnated composite leave, with leaves between 7 and 15 inches long, with a yellowish green color, with 9 to 13 leaves (Click on the image at the right to see it better).

The walnut must not be confused with other trees that have similar leaves. One of these last ones is the ailantus (Ailantus altissima), introduced from China, whose main difference from the walnut is that it has glands with an unpleasant smell. There is also the Chinaberrytree (Melia Azedarach), a plant native to Asia, whose leave is darker than the walnut, and also has an unpleasant smell, as well as taste, and it's fruit, a wrinkled yellow berry, is somewhat poisonous.

We also have the Mexican elder or Tapiro (Sambucus mexicana), which is a tree with bunches of characteristic yellow flowers, and of whose fruit a missionary during Colonial times said: 'The Pimas Altos make from it's fruit a beverage that gets drunk anybody and in three or four days he won't recover; this is the reason that the Jesuit missionaries have tried to extinguish it"