Persea americana  Mill. 1768

pronounced: PER-see-uh uh-meh-rick-AH-nuh

(Lauraceae —  the laurel family)

common names: Avocado, Avocado Pear, Alligator Pear

persea americanaavocado tree Persea is an old name for a tree in the genus (possibly Greek), once sacred to the Egyptians; americana needs no explanation. ‘Avocado’ comes from the Aztec word āhuacatl meaning ‘testicle’, a reference to the shape of the fruit. Historically, avocados had a long-standing stigma as a sexual stimulant, and were not purchased or eaten by anybody wishing to preserve a chaste image! The word ‘pear’ commonly associated with this fruit is also due to the shape, and ‘alligator’ due to the rough skin of some of the cultivars. Avocados are native to Mexico, Central America and South America.

Avocado trees grow up to 20 m in height, depending on the variety. The leaves are alternately arranged, 12–25 cm long. The flowers are inconspicuous, greenish-yellow, 5–10 mm wide. The fruit can be anything from 7 to 20 cm long, weighs between 100 and 1000 g, and has a large central seed 5 or 6 cm long. The fruit is not a drupe, but is technically a berry.

The species is only partially able to self-pollinate, because of the differences in the timing of pollen dispersal from the anthers, and the stigma receptivity of the flowers (known as dichogamy). The timing of the male and female flower phases differs among the various cultivars. They are categorized into two groups, known as A and B. ‘A’ cultivar flowers open as female on the morning of the first day and close in late morning or early afternoon. They then open as male in the afternoon of the second day. ‘B’ varieties open as female on the afternoon of the first day, close in late afternoon and reopen as male the following morning. A variety from one group will usually produce enough fruit in a home garden, but when grown commercially it is found that much greater harvests are obtained by planting trees from both groups.

persea americana fruitfruit persea americana fruitavocados‘A’ cultivars: Hass, Gwen, Lamb Hass, Pinkerton, Reed.

‘B’ cultivars: Fuerte, Sharwil, Zutano, Bacon, Ettinger, Sir Prize, Walter Hole.

Due to the difficulty of pollination and a long juvenile period before avocados fruit, and the fact that plants grown from seed are seldom true to type, most avocados are propagated by grafting on to root stock. Like the banana, the fruit of the avocado matures on the tree, but ripens off the tree. Fruits should be allowed to reach maturity before being picked. They can be kept chilled for quite a long period, and rapidly ripen when brought to room temperature – within a few days, or even more quickly if kept with bananas.

The tree pictured is the Hass cultivar, which ripens with a dark purplish black skin. This is the most important avocado in the commercial market worldwide, accounting for about 80% of all avocados grown. All Hass trees are descended from a single mother tree planted by Rudolph Hass in California in 1926. This tree died at the age of 76 years, being cut down on September 11th, 2002, after a 10 year battle with root rot. Hass trees, like some other cultivars, have the tendency to bear well only in alternate years. After a season with a low yield, such as colder than usual weather that avocados do not tolerate well, the trees tend to produce abundantly the next season. This heavy crop depletes stored carbohydrates in the tree, resulting in a reduced yield the following season, and thus the alternate bearing pattern becomes established.

As the avocado tree is grown for its fruit, its timber is not widely used; but quite a lot of avocado wood is available when groves are thinned out or when tall trees are topped. The sapwood is cream-coloured or beige; the heartwood is a pale red-brown, mottled, and dotted with small drops of gummy red sap. It is a fine-grained wood, moderately soft but brittle. It is not very durable, being susceptible to termites and fungi.

The wood has been used for house building (especially posts), furniture-making, agricultural implements, carving, sculptures, and musical instruments. It also yields quite a good-quality veneer and plywood. It turns reasonably well, is easy to work, dresses and polishes well. It must, however, be carefully seasoned before being worked, as otherwise articles made from it will crack.

The larvae of several Lepidoptera species feed on the avocado plant, including:

• the Ivy Leafroller Cryptoptila immersana;
• the Avocado Leafroller Homona spargotis;
• the Orange Fruit Borer Isotenes miserana; and
• the Sinister Moth Pholodes sinistraria.

 Photographs taken at Picnic Bay 2009

Page last updated 2nd February 2018







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