My own research into the avocado some years ago alerted me to the fact that there are issues with fertility, and suggest that you may nead to get more than one plant to sync fertility or at least get the 'boys and girls' opening at the same time.
Check this link:
http://en.wikipedia.org/wiki/Avocado
which gives you more scientific detail.
The humble Hass avocado has a wonderful history and was a chance seedling that was originally discarded by the grower (along with several others), only to be bought by Hass. The next time you buy a Hass avocado, you can quietly thank Hass's children for having a good palate and the presence of mind to stop their father cutting down the ugly looking fruited Hass avocado tree which now supports an industry worth over a billion dollars worldwide. Amazing effort for just a single plant! The Granny Smith apple is yet another of those classic fruits that nearly didn't gain fame. Back to the avocado, here is some useful history:
"All Hass avocado trees have been grown from seeds (or were grafted from the cuttings) of a single tree which was grown from a seed purchased in 1926 from A. R. Rideout of Whittier, California. At the time, Rideout was getting seeds from any source he could find, even food scraps from restaurants. Meanwhile, Hass would plant three seeds at a time in one spot and later keep only the strongest seedling which grew there.[1] In 1926 a planting of three seeds at his 1.5-acre grove at 430 West Road, La Habra Heights, California yielded one strong seedling.[1] After trying and failing at least twice to graft the seedling with branches from Fuerte trees (which were then the predominant commercial cultivar), Hass thought of cutting down the tree but his children liked the taste of its bumpy, odd fruit and he let it be. The Guatemalen subspecies of the original seed from which the tree sprang is not known and the seed may have already been cross-pollinated when Hass bought it.
Hass patented the tree in 1935 (the first US patent on a tree) and made a contract with Whittier nurseryman Harold Brokaw to grow and sell trees produced from its seeds, with Brokaw getting 75% of the proceeds. Brokaw then specialized in the Hass and often sold out of the trees since the Hass yields year-round (unlike the Fuerte) and has more and bigger fruit with a longer shelf life and richer flavor. The Hass avocado had one of its first commercial successes at the Model Grocery Store on Colorado Street in Pasadena, California, where chefs working for some of the town's wealthy residents bought the new cultivar's big, nutty-tasting fruit for $1 each, a very high price at the time (more than US$15.00 of inflation adjusted value by 2007). However, Hass made a profit of less than US$5,000 from the patent because other growers would use single trees bought from Brokaw to graft entire orchards.
Rudolph Hass carried on as a postman throughout his life and died of a heart attack at Fallbrook Hospital in Fallbrook, California in 1952, the same year his patent expired and not long after he had established a new 80-acre (320,000 m2) orchard.
By the early 21st century the US avocado industry took in over $1 billion a year from the heavy-bearing, high quality Hass cultivar, which accounted for around 80% of all avocados grown worldwide.
Fate of mother tree
Owing to later suburban sprawl in Southern California, the mother tree stood for many years in front of a residence in La Habra Heights. The tree died when it was 76 years old and was cut down on 11 September 2002 after a ten-year fight with phytophthora (root rot). Two plaques by the private residence at 426 West Road mark the spot where it grew. Keepsakes, jewelry and other gifts have been made from the tree's wood by a nephew of Rudolph Hass. Each year in mid-May the city of La Habra Heights celebrates the Hass avocado at its Annual La Habra Heights Avocado Festival."
