• Native vegetation around metropolitan Tucson includes saguaro cactus.Comstock Images/Comstock/Getty Images
  
  In Tucson, chilly and occasionally frosty winter mornings and excessive summer heat limit the number of shade trees that grow well and survive for decades. According to "Sunset Western Garden Book," often summer rains provide more reliable soil moisture than in winter and from March to May, expect lots of wind. Tucson lies in Sunset Climate Zone 12 and U.S. Department of Agriculture Hardiness Zone 9.
  
  

Mesquite

• According to the Tucson's Clean & Beautiful program, the Chilean mesquite (Prosopis chilensis) from South America is the most widely used shade tree in Tucson. If it is occasionally irrigated, the Chilean mesquite grows into a dense-shade tree about 25 feet tall and equally wide.
  
  In the winter when temperatures dip below freezing, the leaves start to drop, but the tree does not become completely bare.
  
  

Blue Palo Verde

• The blue palo verde (Cercidium floridum) is the second most common Tucson shade tree according to Tucson Clean & Beautiful. Tolerant of dry southern Arizona native soils but growing much faster with irrigation, blue palo verde matures up to 35 feet tall and 30 feet wide. Bright yellow flowers rich in pollen fill the entire canopy in spring; this is a primary source of hayfever for locals. It dense branching casts shade even in winter when leaves are gone.
  
  

Willow Acacia

• The willow acacia or Australian willow (Acacia saligna) grows best in soils not overly irrigated or kept dry on the whole. This fast-growing tree for Tucson matures 25 to 30 feet tall and 20 feet wide. If winters are unusually chilly, leaves drop off but quickly regrow in spring's warmth.
  
  

Desert Willow

• Native to the Tucson area, desert willow (Chilopsis linearis) grows 20 feet tall and wide only if it is irrigated according to the Tucson Clean & Beautiful website. Otherwise it remains more a wispy shrub, so irrigate and prune lowest branches to create a tree with canopy to walk under.
  
  

Pistache

• Pistache (Pistacia chinensis) is the only tree in the Tucson desert to turn its foliage scarlet in autumn before dropping away according to "Sunset Western Garden Book." Slow-growing but tolerating a wide range of soil in southern Arizona, pistache reaches about 20 feet tall with equal spread, perhaps a bit larger with irrigation.
  
  

Desert Ironwood

• Native to the Sonoran Desert, desert ironwood (Olneya tesota) trees densely line their branches with thorns. Nonetheless, these extremely long-lived trees make a low-maintenance shade tree for hot areas within Tucson eventually maturing 15 to 45 feet tall with an equal spread regardless of height. The gray-green leaves briefly drop in spring as the fragrant pink flowers appear.