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Scientific: Persea species [Guatemalan (Persea nubigena var. guatamalensis L. Wms.), Mexican (P. americana var. drymifolia Blake), West Indian (P. americana Mill. var. americana). Hybrid forms exist between all three types] 
Common: avocado
Family: Lauraceae
Origin: The avocado probably originated in southern Mexico but was cultivated from the Rio Grande to central Peru before the arrival of Europeans.

Pronounciation: Per-SEE-a SPEE-sheez

Hardiness zones
Sunset 13 (with protection), 15-24
USDA 9 (with ample protection from sun and heat), 10-11

Landscape Use: In Phoenix, protected edible fruit gardens, large accent tree. One cultivar even makes a good espalier.

Form & Character: Variably upright, large and spreading depending on cultivar, dense, mesic, tropical. Some cultivars are columnar, others selected for nearly prostrate form. Clean in appearance, but oh, what a litter producer!

Growth Habit: The avocado is a dense, evergreen, soft-wooded perennial tree, shedding many leaves in early spring. It is fast growing and can with age reach 80 feet, although usually much less in Phoenix. Growth is in frequent flushes during warm weather in southern regions with only one long flush per year in cooler areas.

Foliage/Texture: Opposite, thick, glabrous, lanceolate dark green leaves to 6 inches long, sessile, prominent veins, brittle twigs and small branches; medium fine texture.

Flowers: Flowers are in terminal panicles of 200 to 300, and are small and yellow-green. The flowers are perfect, but are either receptive to pollen in the morning and shed pollen the following afternoon (type A), or are receptive to pollen in the afternoon, and shed pollen the following morning (type B). About 5% of flowers are defective in form, are sterile and abort immediately. Production is best with cross-pollination between types A and B. The flowers attract bees and hoverflies and pollination usually good except during cool weather. Each panicle will produce only one to three fruits. Off-season blooms may appear during the year and often set fruit. Some cultivars bloom and set fruit in alternate years.

Fruits:  West Indian type avocados produce large (weighing up to 2 pounds), smooth round, glossy green fruits that are low in oil content. Guatemalan types produce medium ovoid or pear-shaped, pebbled green fruits that turn blackish-green when ripe. The fruit of Mexican varieties are small (only 6 to 10 ounces) with paper-thin skins that turn glossy green or black when ripe. The flesh of avocados is deep green near the skin, becoming yellowish nearer the single large, inedible ovoid seed. The flesh is hard when harvested but softens to a buttery texture. Wind-caused abrasion can scar the skin, forming cracks which extend into the flesh. "Cukes" are seedless, pickle-shaped fruits. Off-season fruit should not be harvested with the main crop, but left on the tree to mature. Seeds may sprout within an avocado when it is over-mature, causing internal molds and breakdown.

Seasonal Color: None, though the reddish-bronze coloration of new foliage in the spring can be a subtle accent.

Temperature: Intolerant of frost or temperatures in excess of 115oF.

Light: Full to partial sun, no western exposures of sites with reflected radiation. Trunks highly prone to sunscald injury, and are also (like citrus) painted white with a dilute mixture of 50% water and 50% white latex paint to increase albedo.

Soil: Avocado trees grow best in a sandy loam soil. They will not survive in locations with poor drainage due to their sensitivity to root rot pathogens. Zinc deficiency symptoms (interveinal chlorosis) are common in alkaline soil.

Watering: Regular irrigations in desert areas is required.

Pruning: Rarely needs pruning nor should be pruned. The foliar canopy of an avocado tree offers great protection against trunk sunscald injury and should be allowed to extend to the ground if possible. If not, as mentioned above paint trunks with using mixture of 50% latex paint and 50% water.

A special note: Because of its soft-wooded nature, avocado prunage can be difficult to chip and shred.

Propagation: Mostly asexually by cutting, budding or grafting. Seed propagation, though not difficult, is generally not practiced professionally.

Disease and Pests: Avocados are highly prone to pathogenic attack; principally two fungal and one viral species cause more damage than any pest problems. Dothiorella (Botryosphaeria ribis) canker infects the trunk, causing dead patches that spreads to maturing fruit, causing darkened, rancid smelling spots in the flesh. Flesh injury begins after harvest and is impossible to detect on outside. Mexican types are immune to trunk cankers but the fruit is not. The disease is rampant near the California coast and has control measures that are economically viable. Root rot (Phytophthora cinnamomi) is a soil-borne fungus that easily infects avocado roots in sites with poor drainage. Sun blotch is a viral disease that causes yellowed streaking of young stems, mottling and crinkling of new leaves and occasional deformation of the fruit. It also causes rectangular cracking and checking of the trunk, as if sunburned. It has no insect vector but is spread by use of infected scions, contaminated tools and roots grafted with adjacent trees. It is important to use virus-free propagating wood.

Urban herbivory: Squirrels, rats, racoons, birds and all manner of urban critters love to eat the avocado fruits.

Additional comments: The avocado is not suitable for planting in hedgerows, but one can plant two or three trees into a single large hole to save garden space and enhance fertile pollination. For young transplant trees at the beach, in windy inland canyons, or on hilltops one should provide a windbreak of some sort as leaves tatter easily and young branches are soft and weak. Once established however the avocado tree is a fairly tough. Indoor avocado trees need low night temperatures to induce bloom. Container plants should be moved outdoors with care. The roots of avocado trees are highly competitive and in combination with the intense leaf litter will do a nice job of keeping away other vegetation from the base of the tree.

Biomedical notes: The oil content of avocado fruits is rich in oleic acid, a monounsaturated omega-9 fatty acid (also the main component of olive oil). Clinical feeding studies in humans have shown that avocado oil can alter blood cholesterol levels. Leaf and seed extracts have been used for a variety of medical applications including treatment of cancer, blood pressure, vision, depression, inflammation, diarrhea and dysentery, and as an antibiotic.

Some popular avocado cultivars include: