Introduction
Edible trees produce fruits, nuts, seeds and pods that suit human tastes. The trees selected in this booklet thrive in Tucson. Choose trees thoughtfully. Trees need water; the right soil; enough sun, shade and/or chill hours; pollination; space to grow, and care throughout their lifespans.
Tree water needs are key to choosing how many and what type of edible trees to plant. Tucson receives an average of 12 inches of rain per year. Hardy native edible trees can grow just on rainfall once established. Nonnative fruit and nut trees need supplemental water. To save drinking water, use on-site water sources, such as harvested rainwater from basins and rainwater collected in tanks. Harvesting graywater and air conditioning condensate water increase the on-site water supply. Be prepared to use tap water to supplement on-site sources. If you are using drip irrigation, adjust water seasonally according to the needs of the trees.
Soil conditions affect water retention, oxygen and nutrients available to tree roots, and the health of soil microbes. Arizona soils have low organic matter. Native trees can tolerate lower organic matter and higher salt, sand or clay content than nonnative fruit and nut trees. Most fruit and nut trees need well-drained soil around three feet deep. Trees grow best in a mixture of sand, silt, clay and organic material.
Microclimates are small, localized climatic conditions formed by sun, shade, wind, soil and water flow interacting with vegetation and structures in the land-scape. These patterns can affect sunlight intensity, accu-mulated heat, wind and moisture. When choosing and placing trees, select microclimates they prefer. Then har-ness and/or modify microclimates using tree placement, structure placement, irrigation, mulch, sun and frost protection and many other strategies. In Tucson, winter sun and warmth shine on the south side of buildings and trees, with deep shade on the north side of buildings. In summer, it is hot and sunny everywhere. Hot, dry winds tend to blow from the west and southwest.
Chill hours are the number of hours wintering trees must spend between 32°F and 45°F to stimulate fruit development. For trees that have chill requirements, placing them on the north side of houses provides beneficial deep shade in winter.
Pollination is the transfer of pollen from the male to the female part of a flower, resulting in fruits, nuts, berries, seeds or pods. Know how your tree is pollinated.
•Self pollinated: blossoms pollinated by their own pollen or pollen from another flower on the same tree. Only one tree is needed.
•Cross pollinated: blossoms pollinated by another tree of the same variety or another variety of the same species. At least two trees are needed.
•Animal and insect pollinated: trees need moths, bats, birds or insects to pollinate flowers. Be careful with pesticides that could hurt pollinators.
•Wind pollinated: Pollen is transferred by the wind. At least two trees of the same species should be with-in 50 feet of each other.
Heights and widths of trees vary with tree age, planting environment, water supply and pruning. Knowing a tree’s full potential size helps you determine spacing and quantity of trees for your site.
Plant Your Trees
Improve soil, harvest water and create microclimates to provide the water, sun, shade and “chill” conditions your trees need to be healthy and productive in the desert.
Always find out and mark where utility lines are located. Do not plant trees over buried utility lines or under overhead utility lines. Use extreme caution if you are digging near buried utility lines.
Plant the Water. Create passive water harvesting depressions for the mature size of trees and construct a smaller water harvesting basins for new trees. Plant the tree slightly high in the planting hole with a basin along the drip edge of the tree. Keep water and mulch away from the tree trunk.
In Tucson, the best time to plant trees is during October and November. Native desert trees can also be planted in winter and during monsoons when humidity and soil moisture are high. Because extreme heat requires excessive watering, don’t plant between late April and July.
Plant the Tree: Dig a hole twice as wide as the spread of the tree’s roots but only as deep as the root ball. Widen the top few inches of the hole to create a shallow sunken basin about 3 feet in diameter. This will help catch water and allow moisture to filter in slowly to the tree’s roots.
Place the tree in the planting hole with the root ball resting on the bottom. Gently fill soil around the tree and gently compress it to avoid air pockets around the roots. Water trees right after planting so the soil settles firmly.
Top basins with a layer of organic mulch 3 to 6 inches deep; leaves, wood chips, straw, etc. conserves soil moisture, suppresses weeds, reduces soil erosion and compaction, and provides nutrients. Keep organic mulch from piling up against the tree trunk. Add mulch over time to maintain a thick layer.
Watering. Keep newly planted trees well watered until the roots grow into adjacent soil. Water needs are highest in April through June and decrease during July to September monsoons. Water mature trees at, and slightly beyond, the tree’s drip line. Check watering depth by pushing a metal rod or stick into the soil—the rod will stop at dry soil. Periodic deep watering, at least 6 inches down into the soil, encourages deep root growth and more resilient trees.
Feeding. Native trees are good at using nutrients from poor soils and may not need additional inputs. Fruit and nut trees have good root systems to extract water and minerals, but soil nutrients can be used up producing large fruit yields if the soil has insufficient organic matter. Periodically fertilize fruit and nut trees with compost and fresh mulch to encourage new growth and higher yields.
Pruning. While native trees do not need extensive pruning, proper shaping—especially of thorny trees—is important in public spaces. Pruning young fruit and nut trees can promote sturdy branches, distribute sunlight, create more airspace, control size and make trees easier to harvest. Prune within the first few years of growth to promote correct tree structure and early fruiting.
Extreme conditions. Tucson experiences extreme heat, drought, cold and storms. Plant cold-sensitive trees in warm microclimates away from cold air pockets. If freezing is forecasted, wrap sensitive trees in sheets, blankets, cardboard or fiberglass. Most fruit and nut trees prefer full sun, but intense sunlight can burn exposed bark, leaves and fruits. Plant sensitive trees on the east side of hardy native trees or buildings. Hang shade cloth over sensitive trees in direct sun. Mulch to conserve soil moisture.
Tree Problems. To avoid diseases, grow edible trees in diverse systems and keep trees well irrigated, fertilized and harvested. Prune dead and diseased branches and burn or destroy diseased or pest-infested branches. Rake, chip and compost fallen leaves and branches. Plant understory species that attract beneficial insects to prey on any damaging insects. If rabbits, squirrels, or packrats are a problem, harvest fruits early, keep fruit and debris off the ground, hang bright lights at night and keep woodpiles away from trees. Harvest soft fruits early, place bags over fruits and hang shiny objects to deter birds. Interplant with bird-friendly trees to satisfy birds and people alike.
Safety first when harvesting edible trees! Look up for power lines, roofs and overhead obstacles. Look down for holes, tools, cactus, rattlesnakes and other hazards. Sturdy gloves, eye coverings, long-sleeve shirts, long pants and closed-toed shoes can protect you from scratches, pokes and insects. If you manage a group harvest, pay extra attention to ladder and tool safety. Be aware that bacteria, mold, fungus, bird droppings and other materials can contaminate fruits, nuts, seeds and pods, so do not collect off the ground and do not harvest food with dark spots, mold or other problems. This is especially important for mesquite pods.
Harvest times. Harvest times vary with weather, sun and wind exposure, slope, elevation, variety and other factors. Keep your eyes on the trees to judge when to harvest. Mature soft fruits should be harvested right away to avoid decay and beat the birds to them.
Prepare and Preserve. Enjoying the produce from your trees is the fun part! To increase local health and food security, share surplus with family, neighbors. Celebrate the delicious bounty, history, culture and stories of your community’s edible trees.
Apple, Malus xdomestica……………………….. 8
Apricot, Prunus armemiaca…………………. 10
Bay Laurel, Laurus nobilis……………………. 12
Carob, Ceratonia siliqua……………………..14
Kumquat, Fortunella margarita…………….16
Elderberry, Sambucus nigra…………………. 18
Fig, Ficus carica…………………………………… 20
Netleaf Hackberry, Celtis reticulata……… 22
Ironwood, Olneya tesota……………………… 24
Jujube, Ziziphus jujuba………………………… 26
Loquat, Eriobotrya japonica…………………. 28
Mesquite, Prosopis velutina………………….. 30
Mulberry, Morus nigra/rubra………………. 32
Olive, Olea europaea……………………………. 34
Palo Verde, Parkinsonia florida……………. 36
Pomegranate, Punica granatum…………… 38
Quince, Cydonia oblonga…………………….. 40
Saguaro, Carnegiea gigantea………………… 42
Arizona Walnut, Juglans major……………. 44
Understory Plants………………………….. 46-53
Agave, Barrel Cactus, Chiltepin, Cholla, Desert Hackberry, Sonoran Desert Oregeno, Wild Grape, Wild Mulberry, Wolfberry, Yucca, Blackberry, Gogi Berry, Grape, Passionfruit, Pineapple Guava, Spineless Prickly Pear.
