Life Zones: Upper Sonoran – Plains

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 on 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.

Cholla Cactus

Throughout the zone, 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, Elephant Ear, Barrel Cactus, Organ Pipe, Cholla and many other unique species.

While many of us have Christmas cacti and Moon cacti, that we enjoy indoors, the closest plant relatives to the cactus that you may find among your garden flowers are violets and begonias.

Prickly-Pear Cactus

Native American tribes prize the fruit of the Prickly-Pear Cactus, which they can boil and mash. 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.

Ocotillo

This spindley looking cactus is indigenous to the Mojave, Sonoran, Chihuahuan and Colorado deserts in the Southwestern United States. While ocotillos look dry and nearly desiccated on the outside, but they are semi-succulent; it is actually more closely related to the tea plant and blueberries than to cactuses. It regenerates leaves after rainfall. The name ocotillo comes from the Nahuatl word ocotl meaning “torch.” This cactus is also known as buggywhip, coachwhip, candlewood, slimwood, desert coral, Jacob cactus and vine cactus.

Saguaro Cactus

Most cactus flowers are large and colorful, making them attractive to pollinating insects and dry-scape gardeners. The Saguaro is known and prized for its size and outstretched branches that look like “arms.” They are also known for their cavities, where birds (cactus wren, for example) make nests and avoid the land preditors below them.

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. It is also called Sundrop, Evening Star, German Rampion, Hog Weed, and even Fever-Plant.

Golden Rod

One of the prettiest yellow flowers, this plant gives many people nasal fits. It is among the most allergy inducing headaches. We love the Golden Rod for its color. It blooms during the same season as ragweed, another allergen, but it is bothersome to many people with allergies nonetheless. It grows in profusion along roadsides and makes for a lovely sight, when the windows are shut.

Mullein

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