WANT MORE MANGOES NEXT YEAR?

(One of a series of articles about growing fruit trees in Samoa, written by Digby Gotts and published in the 'Samoa Observer' between December 2000 and April 2001)

So the mango season is over for another year. How many fruit did your tree give you? For many of the mango trees in Samoa, the answer would be few or none. The rain, heat and humidity produce perfect conditions for the growth of various fungal diseases that kill the flowers and force fruit to drop early. There is not much the grower can do to change the weather, but there are a few things that you can do to help your tree fight off the diseases without chemicals and the time for action is almost over for the year.

Rain on flowers is the main killer so the aim in this exercise is to get the tree to make flowers during the dry season in August or September when they have the greatest chance of staying dry and disease free. On mango trees, flowers develop on the ends of new leafy growth after those leaves have grown then rested for 4 months or so. Fruit will be formed if the flower is pollinated successfully, (bees help), and fungi do not develop in the dying flower. I’m sure you’ve seen how when mango trees have branches cut or broken, they characteristically grow many new shoots along the remains of the branch. If you can force the tree to make new shoots before March, they will be around 5 months old and ready to flower for the dry season. So chop off the branches!

Radical? Yes, but what have you got to lose?

Take out the centre of the tree at whatever height you are comfortable to work. (For me that’s about 2 m from the ground). Leave the tree with the centre open to the sky. This will allow air movement helping the tree to dry out and kill off growing fungi. Now move around the tree cutting off every vertical branch, limiting the final height to about 3-4 meters, and taking the leafy ends off every spreading branch. You should now have a spreading leafless skeleton of a tree, not much good for shade for a while, but it will repair itself. New shoots will appear within two weeks and when these are about 2 months old you may need to go through and thin them. Remember that the goal is an open spreading tree. So remove the shoots growing towards the centre, and where they appear to be too close together. Leave the strongest and the outward spreading shoots.

So if you can cut back your mango before the end of February, the new growth can be 6 months old by July/August and the flowers will appear for the drier time. If you leave the pruning until March, the new growth may not have enough rest time to flower during the dry. But it might. And that’s what makes this an art form.