DURIANS IN DARWIN 1990
SCIENTIFIC NAME: Durio zibethinus
FAMILY: Bombacaceae
To my knowledge, 2 durian trees fruited in Darwin in 1990, probably a first time in the N.T. A stressed tree in the Kaissis orchard in Humpty Doo also flowered very heavily but set no fruit.
The two fruit produced were harvested between Christmas and New Year and had flowered around early to mid-September. The first picked was variety 'Mon Tong', now known to be 'Gumpun' - a tree in the orchard at Berrimah Farm.
It was a well-formed fruit, fully filled in all segments and had very small seeds. Its flavour was definitely durian, the texture and creaminess were particularly good for a first fruit. The tree was planted in 1984, and unfortunately, is now dead. This may have been the reason that the tree fruited. It was found looking a little parched as the mini-sprinkler had been blocked for some time. This probably induced flowering, and the tree survived long enough to see the fruit fully-ripened, but died shortly afterwards.
I performed a similar trick on one of my own grafted trees by blocking off the sprayers for 10- 12 days. This succeeded in mid-dry in causing a massive leaf drop, I estimated at well over 80%. The tree was well-watered afterwards and the tree recovered fully within 6 months, however there was no sign of flowers on this tree, a D123.
My fruiting tree was a younger 'CHANEE' now thought to be a 'GOB'. There were a large number of flowers produced but only one fruit set. I am also unsure whether it was produced naturally or the result of me fiddling a little with the pollination. I was told how to do it later on, by collecting pollen in the morning and then brushing on the pollen with a fine paintbrush early next evening. My pollination occurred at collection time at night. The fruit was not fully-filled. In two segments only was there any flesh, the rest of them empty. One segment of the 5 had one seed, and this seed was approximately 80 mm long and approximately 25 mm in diameter, the largest durian seed I have ever seen.
The fruit itself weighed in at over 3 kg.
Members tasted the flesh at the February indoor meeting this year. It was a little on the firm side, but this is apparently not uncommon in the first fruitings.
Even three layers of plastic failed to prevent the odour of the flesh from permeating the freezer compartment of the fridge.
I had two problems with this fruit. Firstly, a tanny-brown-coloured rat took a liking to the fruit and used to spend many nights chewing off a few more of the sharp spines of the fruit. I finally tempted him to a meal of rat block left on top of the fruit. There were no more rat visits, but it certainly ruined the visual appeal of the fruit.
Another problem, which may have been due to the rat chewings, was just before ripening; the fruit developed a black spot on the surface which slowly enlarged. When the fruit finally dropped (I had a piece of baler twine to keep it suspended to its branch), this black mark had penetrated to the flesh and was starting to cause discolouration of the flesh nearest the mark and this had to be discarded.
I have also had one tree which began to lose leaves and die back on one side of the tree and then progress rapidly upwards. This tree I injected with phosphorous acid (the treatment for phytophthora in avocadoes) and reversal of symptoms was noted within 3 weeks of trunk injection.
Another problem, which can be disastrous if not found early, is a trunk-boring larva which can eventually ringbark a tree. Always keep an eye out for their trails. Considerable damage can be done under the bark before it is noticed. This same borer I have found working Marang, River red gum, African mahogany etc. They can leave a trail up to 20 mm wide as they feed around under the bark. A pocket knife is useful to pare away the affected area and to find the offending creature, which can be up to 40 mm in length and 8 mm in diameter. It is usually just under the bark, but sometimes it will burrow into the sapwood. A piece of wire pushed into this hole will effect a speedy end to this destructive beast.
There are several pitfalls in growing durians, but I feel the most common is drought. They must have regular watering, and the soil should never be allowed to dry out, particularly on the surface. A hay mulch for the first 5 years is an excellent investment. I use Nitrophoska plus trace elements as a fertiliser, usually about 4 applications per year, mostly during the wet season.
DATE: September 1991
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