This grafted avocado tree grows in front of my house in Kuala Lumpur. It was planted in June 1997 and first flowered in Mar 2002 but did not produce fruits. It next flowered in May 2003 and produced 55 fruits. Since then it has fruited at unpredictable intervals, roughly once a year, the last time producing 156 fruits. This picture was taken today, 9 Oct 2011. The tree has been kept small by pruning. It is about 12 ft tall and 12 ft in diameter. Without pruning it would have grown to over 30 ft tall and the fruits would have been out of reach. By keeping the tree small, I was able to harvest all the fruits by hand or with a long-handled fruit-picker.
The flowering month varies from year to year: in this case the sequence was Mar 02, Dec 02, Mar 04, Aug 06, Mar 07, Nov 07, Jan 09, Jan 10, Feb 11.
In modern fruit orchards, trees are kept small by pruning so that fruits can be harvested carefully. Any fruit that hits the ground is effectively damaged because the tissues will be bruised at the point of impact.