By Erica Faber – Technical Manager
Understanding avocado flowering can be confusing and can have a significant impact on your orchard’s production. For our newer growers, as well as our seasoned growers, I thought I would use this opportunity to revisit and feature a topic that is arguably one of the most important stages of growing avocados –
flowering, pollination, fruit set and ultimately orchard productivity.
Pruning, moisture management and nutrition are also important at this critical time. It is also the time of year we are harvesting and planting out new orchards so I have included links to plenty to read up on below to support your actions.
A mature avocado tree can produce more than one million flowers with fruit set ranging from 0.3-0.5%. The avocado flower is very unique in that each flower has a distinct male and female phase which is nature’s way of encouraging cross pollination between different cultivars and ensuring species diversity. This however does not preclude self and close pollination within the same cultivar as is demonstrated in orchards of only one cultivar or individual trees in home gardens.
Briefly explained, avocado cultivars can be divided into either A or B flowering cultivars.
For A-flowering cultivars e.g. Hass, the flower will open for the first time (day one) functioning in the female phase with only the female parts being receptive. The flower then closes after two to six hours and reopens in the afternoon of day two in the male phase, with the male flower parts now being functional and shedding pollen.
The flower remains open and finally closes for the last time the next morning. If pollination and fertilisation was successful, the flower will remain on the tree and begin to form a fruit. If fertilisation was not successful, ethylene will be produced at the base of the ovule and the flower will abscise (fall off).
For B-flowering cultivars e.g. Zutano, the flower opens on the afternoon of day one in the female phase, closes and reopens from the morning to afternoon of day two in the male phase, synchronising with the opening of the A-cultivar in its female phase. Pollen transfer from the B cultivar to the A cultivar can then take place.