Life Zones: Upper Sonoran – Plains

In the Zone

The Upper Sonoran Plains Zone is relatively flat compared to higher zones. Clay soils are still the rule, but the hills and valleys were carved from granite. Rainfall is a little more plentiful than the desert below. These conditions limit the native vegetation throughout this zone to species which can tolerate long periods of drought, and thrive on sunshine with the heat in summer and cold in winter. Originally native grasses covered these zones with a fairly tight sod. Over time the grass islands have been broken into windblown patches and cut by streams. Trees on many Upper Sonoran streams are similar in the Lower Sonoran zone: the alder, willow and cottonwoods are common along permanent streams, cactus and manzanita survive in the dry gullies.



Cactuses (or cacti) are the Western Hemisphere’s succulents and they are abundant. They are recognized by their fleshy, leafless green stems, often covered with clusters of spines, which can be nasty to extract from your skin. Two hundred species of cacti are native to the US. We saw Saguaro, Ocotillo, Prickly Pear, Cholla and many other species. The closest related common garden and house plants to cacti are violets and begonias.


Most cactus flowers are large and colorful, making them attractive to pollinating insects and dry-scape gardeners.


Prickly Pear Fruit – “tuna” of the Cactus realm

Native tribes prize the fruit of the Prickly-Pear Cactus, which they can boil and mash, and some animals feed on the fruit as well. The stem cells of the cactus store water after rains and the plants organs are designed to preserve water (prevent moisture loss), especially in the hot and dry seasons. Some cactus varieties can withstand up to two years of drought.


Sacred Datura

Datura is a member of the potato family. This conspicuous plant has a large trumpet-sized and shaped bloom. The flower is bright and   white. It opens at night and wilts or closes in the bright morning sunlight. A single plant can have up to 100 blossoms at a time. The plant has several names including Jimsonweed, Sacred Thorn-apple, Indian Apple  and Angel Trumpet.

The plant is poisonous to eat, especially the seeds, and it has been used by some cults and Native tribes to induce a stupor and hallucinogenic dreams. The plant must be handled with caution because it contains a deadly narcotic akin to atropine.


Yellow Evening Primrose

You will find this plant most commonly in the road cuts and in places where the soil has been disturbed. The species has showy yellow flowers with four heart-shaped petals.

How to Grow and Care for Evening Primrose

They are prolific bloomers and generally bloom at night.


Golden Rod

One of the pretty yellow flowers that gives people the most allergies might be Golden Rod. It grows and blooms the same time of the season as ragweed, but it is bothersome to people with allergies nonetheless. It grows along roadsides and makes a pretty sight, when the windows are shut.



This plant grows to over 6 feet tall and is sometimes thought of as a golden rod, but it is a plant that flowers every other year and is a traveler from other parts of the world to the western US. Originally from Europe and Northern Africa, it was introduced to the States and Australia, so it grows on all but Antarctica. The leaves are soft and serve as a good substitute for toilet paper, when you are in a pinch.