Tropical and subtropical fruits (2+1)

Flowering and pollination

Grape vines, like many other fruit types, are self-pollinated where the female and male parts needed for pollination are present on the same plant. If you can recall your biology lessons from school, you will remember that there are certain things that need to be present for a flower to be a perfect flower.
Female part (pistillate)

This is the central part of the flower and consist of basically 3 things

• The stigma – the soft tissue at the end of the pistillate, where pollen is accumulated
• The style – a tube where through the pollen will move to reach the ovary
• The ovary – the place where the fertilisation takes place
When you look at the a grape flower, you will notice the pollen-carriers (stamina), these are the male parts of the flower.

Male part (stamen)

This is the outer part of the flower, just underneath the petal and consist of basically 2 things

• The anther – the place where pollen is produced
• The filament – a long stem that supports the anther at it’s tip
For your grape vine to pollinate, all of these parts must be present in a grape flower. Certain wild grape varieties, do not have male or female parts on their flowers and is called dioecian plants. Cross pollination needs to take place for these grape vines to bear fruit. Most of the commercial grape varieties used these day are self-pollinated and do not need cross-pollination in order to bear fruit.
During pollination, the pollen from the anther of the male part of the flower, falls on the stigma of the female part, and grows down the style until it reaches the ovary, where it will penetrate the wall of the ovary so fertilisation can take place.
Dramatic climate conditions (wind, rain, and extreme cold and extreme heat) can have a negative influence on how well pollination will take place. Mild, sunny weather is ideal.
During poor pollination weather, you will notice that grape clusters will be straggly and very loose, with not many berries on the clusters and the opposite happens with too good pollination weather – the grape clusters is too compact, deforming and damaging nearby berries. This is often the starting point for secondary infection (botrytis or grey rot).
There isn’t much you can do about to straggling grape clusters, but in the case of compact bunches, you can thin out the bunches by removing berries by hand or blunt scissors. DO NOT work with scissors in a bunch after the berries softened – you will damage the surrounding berries and this will be were infection can start. Try to thin out the bunches when berries are still green (the size of small peas)