Depending on rainfall, the desert can be ablaze with color in the spring. Rainfall varies from 9 inches on the east to 3 inches on the west, with the valleys receiving less than the mountains. The driest period is between April and June when ninety consecutive days of 100 degrees Fahrenheit are common. Daytime winter temperatures are in the 70s.

One always marvels at the desert cactus plants, their beautiful flower displays, and ability to grow and thrive on such meager amounts of rainfall. Both the chain-fruit and teddy-bear cholla grow in the form of large shrubs with joint connections that are so brittle they easily break off as if to jump at the animal or person who brushes it. Fruits of the chain-fruit cacti are a major source of water for pronghorns. Although at its western limit, giant saguaro cacti in the refuge are more than just a trademark of the southwest. Insects feeding on nectar will attract flycatchers, their fruits are eaten by birds and those that drop are consumed by various earthbound animals. Gila woodpeckers setup housekeeping in the tall, fat stems of the saguaros.

Creosote bush, commonly called greasewood, and bur-sage are the most common plants in the desert. Creosote bushes are conspicuous by their even spacing, with root systems reaching out and competing with all but annual desert wildflowers. Bur-sage, the hay-fever plant of the desert, is highly effective in stabilizing the loose soils in the alluvial washes called bajadas at the base of mountain slopes. What might surprise people unfamiliar with desert environments, however, is that 420 plant species representing 65 families have been thus far documented in the refuge. No endangered plant species have been identified, but several rare plants including blue sand lily and senita cactus are present.

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