Avocado – Persea americana (over 1000 cultivars)
To the untrained eye, the foliage of this tree might be mistaken for any number of species bearing glossy, succulent, smooth-margined evergreen leaves. I have to confess, back in 1998 when I walked San Diego utility lines for potential hazard trees, I initially confused this tree with the beautiful Southern Magnolia. However, the dead giveaway usually lurked under the heavy drooping branches, where one-of-a-kind, pendulous fruits appeared in abundance. Indeed, the Avocado could be one of Southern California’s most underestimated trees.
True to its name “Persea americana”, the Avocado is a Native American tree, originating in sub-tropical Latin America, and later bred to survive the cooler Mexican highlands. Although it didn’t land in California until the 1850’s, it had been revered by ancient cultures for millennia. In fact, the etymology of the word “avocado” is said to be derived from the Aztec/Nahuatl word “ahuacatl”, meaning “testicle”; ostensibly named for the shape of the fruit, which botanically is considered a berry. It was even rumored to be an aphrodisiac, and therefore shunned by respectable European society of the time. 
Unique in the plant world, avocado flowers are bi-sexual. In A varieties, the female organ opens in the morning, then closes and reopens the following afternoon as male. In B types, the reverse occurs. Fruit set can be limited unless inter-planted for cross pollination, although temperature also plays a role. In frost free zones, there are now 100’s of distinct cultivars. They provide a nearly year-round rich source of mono-saturated fat, higher fiber content than other fruit, and are sodium and cholesterol free.
With heights ranging from 15-60 feet, they become fine ornamental landscape specimens in zones 9-10, holding their own in a climate of nearly infinite choice. Despite notoriously shallow roots and a need for perfect drainage, they adapt to inhospitably rugged slopes as they mature into bountiful wonders. Once fully grown, their dense canopies hold moisture throughout the year; in fact avocados are noted as a fire-resistant species. With year round air quality issues, two mature avocado trees can remove the amount of carbon dioxide the family car produces in over four years time.  Perhaps as the American diet yearns for better nutrition and sustainable environment, we should all pick some fruit on the way in the door.
- Robin Y. Rivet, ISA Certified Arborist, San Diego Regional Urban Forestry Council