NEW MANGOES FOR QUEENSLAND
Topworking your backyard mango

SCIENTIFIC NAME: Mangifera indica
FAMILY: Anacardiaceae

Probably several members are faced with the same problem as I had - one or two mango trees in the back yard that were of inferior varieties. I decided to have a go at topworking two trees in my yard that were producing large quantities of fruit of indifferent quality.

The first step is to skeletonise the tree, that is, to cut off all the branches 30 to 60 cm from the main trunk. It is vital to do this at the correct time, i.e. immediately after the tree has fruited, so that the new growth that springs up from the ends of the stumps of the branches will be mature enough to be grafted onto well before the end of the wet season.

Some experts on grafting suggest that topworking should be done by inserting the graftwood into slits in the bark on the stumps of the branches on the rootstock tree, but I have had no success with this method. I believe the chances of success are much higher if you allow the stumps to send out shoots, which they will do in profusion, and then graft onto the shoots when they are about one centimetre in diameter.

The shoots on the rootstock should be ready for grafting by about the end of February. About a week before you intend to do the grafting, the scions should be prepared on the trees from which you intend to take the graftwood. This is done by selecting tips of branches which are showing clear signs of being about to send out a new flush from the centre of the tip, or to send out one or more buds round its periphery, but from which the new flush or buds have not already actually erupted. On the selected branch tips, all the leaves should be snipped off over a length of about 15 centimetres from the tip, leaving about two centimetres at each leaf petiole (the leaf stem) still attached. After about a week, these stumps of the leaf petioles should either fall off themselves or be easily detachable. When the petioles have dropped off, the 15cm lengths of graftwood can be cut off, placed in a polythene bag and kept cool until you are ready to graft them. They should not be kept in a refrigerator and should preferably be used for grafting within 24 hours.

It is quite feasible to topwork scionwood of three or four varieties onto a single tree, but, if you do this, make sure that the varieties of scion that you select are of approximately equal vigour. It is useless to mix vigorous varieties, such as Kensington or Haden, with dwarf or semi-dwarf varieties like Nam Dok Mai or Irwin, since branches onto which you graft the vigorous varieties will take over and crowd out the less vigorous ones. I grafted three varieties, Haden, Strawberry and Irwin, onto one of my trees, and am finding that the branch with the Irwin graft is being crowded out by branches onto which the other two more vigorous varieties were grafted.

I used the ordinary wedge-grafting technique to graft onto the shoots on the branch stumps of the rootstock tree, and found I had about a 50% success rate. So do not cut off the shoots that you do not use in your first attempt at grafting. You may need them for a second or third attempt. Make sure that you place a polythene bag over the grafted shoots to maintain the humidity until the graft has definitely taken, i. e. for about two weeks. One or more leaves from just below the graft should be pulled up into the bag to help keep the humidity level up, and to shade as much as possible of the scionwood from the sun.

All being well, your renovated mango should produce fruit of the grafted varieties after three years.

David Dundas

DATE: September 1990

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