Arizonensis --> Sonoran Desert Naturalist --> Sonoran Desert Places --> Estrella Mountain Park --> Estrella Mountain Wilderness

Estrella Mountain Wilderness
Maricopa County, Arizona


One of four wilderness areas within a short driving distance of Metropolitan Phoenix, the Estrella Wilderness is perhaps the least visited and the most difficult to reach. For sure, during much of the summer this is an inhospitable desert location with extreme temperatures, little shade and no water. Yet as Edward Abbey said, there is 'there is something about the desert'. The word ‘estrella’ means star in Spanish and indeed the highest peaks in this range reach for the stars above the low surrounding deserts. The name could also refer to the abundant, sparkling flakes of mica present in the Precambrian schist. The eastern half of the range is part of the Gila River Indian Community and access there is restricted. The northwest quarter of the range lies within Estrella Mtn. Regional Park and is now bordered by housing developments and has been incorporated into the city of Goodyear.

Access to the Wilderness Trailhead is at the east end of the broad Rainbow Valley south of Goodyear, Arizona. Various agricultural, livestock and housing schemes have disrupted the desert soils in the valley allowing for erosion, patches of weeds, and piles of junk. Prevailing winds from the west have deposited a thick layer of sand and silt along the windward side of the north-south oriented Estrella Mountains range. This low desert against the mountains is the closest sandy desert to the Phoenix area and luckily it is protected from development by wilderness designation. Few other flat areas in this area are left in such a pristine condition. Caution: Deep sand in the roads requires four wheel drive.

From Phoenix drive west on I-10 and exit at Estrella Parkway. Turn south and drive to Elliott Road in the Estrella Ranch development. Drive west on Elliot about 2.6 miles to Rainbow Valley Road. Rainbow Valley Road runs south through the valley - after 9 miles turn east on Riggs Road. Now 5.3 miles east on Riggs Road, with the last several miles narrow and sandy, ending at the power lines. Two miles south through deep sand along the power lines, and then another two miles east through more sand to the BLM Trail Head and kiosk. Be sure to sign the trail register if you hike.

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Field Trip Reports:
March 29, 2009

More than 50 days have passed since the last measurable rainfall and so virtually all of the spring annuals have dried and gone to seed. Arriving at the Trail Head I found just two other vehicles parked and as I hiked I didn't see any other hikers; this was the solitude I was hoping for. I found the trail up Quartz Peak steep and slippery in spots but it was well graded and marked all the way despite the warning at the kiosk that the trail was hard to follow. Just a kilometer up the trail I found the first of the Elephant Trees (Bursera microphylla). So called because their trunks are very large in diameter as compared to the remaining branches. The dark evergreen leaves are pungently aromatic, just like its close cousin, frankinsence. Some of the ocotillos were still leafed out, while others were dropping their leaves as drought deciduous shrubs.

The cacti were in glorious blooming state, especially Buckhorn Cholla (Cylindropuntia acanthocarpa) and Engelmann Hedgehog Cactus (Echinocereus engelmannii). I was looking for blooming Rock Hibiscus (Hibiscus denudatus) and found many plants with developing seeds before finding just one with an open flower. Several huge nests made from spiny cholla segments belonging to Whitethroat Woodrat (Neotoma albigula) were seen along trail. Birds were scarce except for plenty of Rock Wrens (Salpinctes obsoletus) and a couple of Ash-throated Flycatchers (Myiarchus cinerascens).

Two kinds of ants were out foraging. Most conspicuous were Desert Harvester Ant (Messor pergandei). They were busy gathering seeds from the spring annuals and carrying them undergound. The other abundant ant this day were Honey Pot Ants, Myrmecocystus, so called because some workers are delegated to serve as storage vessels in underground chambers. The delegated workers are fed enormous quantities of sugar water until their bodies extend into huge blobs containing essentially honey and leaving the ant immobile. Dale Ward has some great photos of Honey Pot Ants. Up the trail a number of California Checkerspot (Chlosyne californica) were visiting Trixis flowers and sunning on boulders.

Rock Hibiscus

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California Checkerspot

photo © M.J.Plagens

Sonoran Collared Lizard (Crotaphytus nebrius) - Photo by Mike Plagens.


In order of Abundance:

  1. Side-blotched Lizard (Uta stansburiana) -- most active lizard during cooler parts of year. Dark patch behind forelegs; bluish throat.
  2. Western Whiptail -- Cnemidophorus tigris
  3. Sonoran Collared Lizard -- Crotaphytus nebrius


More common species first ...

  1. Buckhorn Cholla -- Cylindropuntia acanthocarpa
  2. Teddy Bear Cholla/Jumping Cholla -- Cylindropuntia bigelovii
  3. Saguaro Cactus -- Carnegiea gigantea --
  4. Engelmann Hedgehog Cactus -- Echinocereus engelmannii
  5. Graham′s Pincushion Cactus -- Mammillaria grahamii --
  6. Compass Barrel -- Ferocactus cylindraceus

Buckhorn Cholla

Shrubs and Trees

In order of Abundance:
The more common species are listed first.

  1. White Bursage -- Ambrosia dumosa -- The most common bursage on flats near mountain.
  2. Creosote Bush -- Larrea tridentata
  3. Foothills Palo Verde -- Parkinsonia microphylla
  4. Desert Mistletoe -- Phoradendron californicum
  5. Brittlebush -- Encelia farinosa -
  6. Desert Trumpet -- Eriogonum inflatum
  7. Desert Ironwood -- Olneya tesota
  8. Desert Globe Mallow -- Sphaeralcia ambigua
  9. Lance-leaf Ditaxis -- Argythamnia lanceolata
  10. Ocotillo -- Fouquieria splendens --
  11. Triangle-leaf Bursage -- Ambrosia deltoidea -
  12. Elephant Tree -- Bursera microphylla
  13. Desert Lavender -- Hyptis emoryi
  14. San Felipe Marigold -- Adenophyllum porophylloides
  15. White Ratany -- Krameria erecta -
  16. Big Galeta -- Pleuraphis rigida - on sandy flats
  17. Desert Wishbone Bush -- Mirabilis laevis
  18. Trixis -- Trixis californica
  19. Chuparosa -- Justicia californica
  20. Janusia Vine -- Janusia gracilis
  21. Ragged Rock Flower -- Crossosoma bigelovii
  22. Rock Hibiscus -- Hibiscus denudatus
  23. Shrubby Bedstraw -- Galium stellatum
  24. Spiny Haplopappus;Lacy Tansy Aster -- Machaeranthera pinnatifida
  25. Odora -- Porophyllum gracile
  26. Desert Agave -- Agave deserti

Lance-leaf Ditaxis

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White Flowers

  1. Emory Rock Daisy -- Perityle emoryi
  2. Shrubby Bedstraw -- Galium stellatum

Pink/Lavender Flowers

  1. Engelmann Hedgehog Cactus -- Echinocereus engelmannii
  2. Desert Lavender -- Hyptis emoryi
  3. Rock Hibiscus -- Hibiscus denudatus

Orange Flowers

  1. Desert Globe Mallow -- Sphaeralcia ambigua
  2. San Felipe Marigold -- Adenophyllum porophylloides
  3. Desert Globe Mallow -- Sphaeralcia ambigua

Yellow Flowers

  1. Buckhorn Cholla -- Cylindropuntia acanthocarpa
  2. Blue Palo Verde -- Parkinsonia florida
  3. Creosote Bush -- Larrea tridentata
  4. Desert Trumpet -- Eriogonum inflatum
  5. Brittlebush -- Encelia farinosa
  6. Trixis -- Trixis californica
  7. Lacy Tansy Aster -- Machaeranthera pinnatifida
  8. Sweet Bush -- Bebbia juncea
Lacy Tansy Aster

Red Flowers

  1. Ocotillo;Coachwhip -- Fouquieria splendens

Blue/Purple Flowers

  1. Odora -- Porophyllum gracile

Greenish Flowers

  1. Lance-leaf Ditaxis -- Argythamnia lanceolata
  2. Brittle Spine Flower -- Chorizanthe brevicornu
  3. Big Galeta -- Pleuraphis rigida

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