THE AVOCADO: AN INTERESTING PLANT

Avocado fruit (a.k.a. as the “alligator pear”) is well known to grocery-store shoppers. The earliest known fossil record of this fruit is Persea umbrellularia, an early or middle Eocene avocado species found in California (Schroeder, 1968)! This occurrence is a relic of a Caribbean flora because the avocado is native to Mexico and Central America. Thus, if the avocado had a pre-Eocene history (when exactly, however, is yet to be determined).  

The avocado plant likely diversified during the Pleistocene, sometime between 1.3 million and 430,000 years ago. Its fruit was undoubtedly eaten by now-extinct prehistoric mammals, such as ground sloths, glyptodonts, and gomphotheres (see my previous posts on these prehistoric animals). The fruit was probably (and still is) also a food source for bears.

The avocado was first “domesticated” by farmers, about 5,000 years  ago, when it became prized for its large and healthy fruit. It grows as a berry tree, with a single very large nut, per fruit. 

The avocado is high in fiber and rich in the vitamins C, E, and K. It is a foliate plant, and is healthy for promoting red-blood cells in the human body. It also contains magnesium and potassium which help to maintain blood-sugar and blood pressure levels. If you are interested in the modern history and/or medicinal aspects of avocados, there are many online videos readily available. 

The classification of an avocado plant is:

Kingdom Plantae

Order Laurales

Family Lauraceae

Genus Persea

Species P. americana

Avocado trees do best in tropical and subtropical climates. [note: many years ago, while doing field work, I came across a sizeable avocado orchard atop the Simi Hills (immediately west of the San Fernando Valley) = a Mediterranean climate in the Los Angeles area of southern California. There were hundreds of trees in that orchard. I think that the orchard has been replaced by new homesites.

From a seed, it takes 5 to 13 years for the avocado to grow into its mature-tree form. These trees can live for 200 to 400 years, but their fruit is only produced in the first 20 to 30 years or so. These trees like to grow in full-sun conditions.

1. Exterior of a “Hass” avocado from Mexico. This avocado” is 3.5 inches (95 mm long) and 2 inches wide (50 mm). Its “skin” is thin (0.5 mm thick) but strong.

2. Interior of the same avocado, with its “meat” present, surrounding the interior nut.

3. Interior of the same avocado, but with the “meat” extracted and the nut fully exposed. The meat occupied about 40 percent of the interior volume of this avocado.

4. Cross-section of a nut extracted from the inside a different avocado. A paper-thin sheath cover around the nut fell apart. This nut is 1.25 inches (28 mm) long and 1.25 inches (28 mm) in diameter. The small seed (5.5 mm length) can be readily seen in the upper part of the image.

Reference Cited:

Schroeder, C.A. 1968. Prehistoric avocados in California. California Avocado Society Yearbook 52:20–34. [online pdf free).