MURPHY'S LAW OF BOTANY - for every good rule there is always a good exception.

Expect young trees on planting out into the orchard to need some shading (particularly the trunk) until they have a useful leaf canopy of their own to protect the trunk and shade (cool) the soil around the root system. If needed, it is a job to be done within a day or two of planting out. The source of the 'sunburn' may be direct sun or in hot weather it may be heat reflecting from bare ground Sunburn is often severe before it is noticed Bark death may have occurred well before obvious signs show up. I have seen in some orchards young trees with only a sparse canopy, and 1-1.5 metres of stem fully exposed to summer sun. The trees are surviving. It is my belief that some form of trunk shading would markedly improve the growth of these trees.

The same situation applies if a mature tree is cut back to a stump ready for grafting. Yes the tree will survive, but it would be a lot happier if the trunk had some sun protection.

Sun on developing fruit will not usually burn the fruit You can however expect sunburnt fruit in situations like having a branch removed and suddenly letting full sun onto the fruit Pineapple fruit stalks will often bend over as the fruit is in the last month or two of maturity. Some form of shading eg shredded paper will be needed promptly before the fruit has a chance to burn eg a couple of hours of summer sun.

This is a job that fits into the day before yesterday category of priority.

Monocots (short for Monocotyledons) are the grassy-type plants. Grasses, Bamboo, Palms, Onions. Sedges, Orchids, Bananas. Heliconias, Philodendrons, Caladiums and Dracaenas to name a few, are all monocots. Trees, most vegetables, and all those not fitting the above, excluding pine trees, are all dicots (dicotyledons). Pines are neither monocots or dicots.

In the monocot group, stem thickening occurs only in the terminal meristematic areas. ie the growing point and the area just behind the obvious growing point. Thickening is a combination of sufficient sunlight for the species X adequate nutrient X stem movement. There is little if any stem thickening further back along the stem. So in crops like palms, a good level of nutrition is needed to grow a thick stem (all relative for the species concerned) at the time when the growing point is being developed In most cases skinny palm trees remain skinny for the rest of their life. ie a skinny palm tree planted can not be made into a fat palm tree. A fat palm tree has had good and adequate nutrition all its life.

So what about those tall bamboos? The first stem is relatively short. The growth of the next stem will be boosted by nutrient from the mother plant (albeit small). And so the bamboo stems go on getting larger and longer with each new trunk, and the mass of mother material behind increases. But still all that stem thickness is laid down sometime in the past, when the piece being inspected was the growing point, ie, the meristematic area.

There is no secondary thickening going on. Grasses grow in the same way as bamboo with each new stem being larger than the previous one until the mature height is reached. In the nursery industry, this principle is very important in the propagation phase where 'thick' vigorous sections make the best propagation pieces.(Some of the Dracaenas eg D. draco, the Dragons Blood tree of the Canary Islands and D. fragrans (Happy plants) and a few others do have secondary stem thickening.)

With dicots, stem thickening is occurring all through the life of the plant A weak stem can, with good nutrition and water be grown into a thick stem. In spite of this example, good nursery practice demands thick vigorous plants from when growth start.

COMPOUND FRUITS - Their ripening
Pineapples, Monsteras, the Annona/Rollinia species and the jakfruit-Breadfruit complex are all compound fruits, ie, each of those segments is a separate fruit which, over evolutionary time, has fused to the adjacent segment (fruit). The way these fruit ripen depends on the sequence that the flower buds mature and open.

Pineapple and Monstera flowers mature and open over a period of 7-14 days. The effect of this spread of flower maturity continues throughout the development of the fruit accounting for the range of ripeness from bottom to top at maturity.

The Jakfruit-Breadfruit and the Annona-Rollinia groups flower over a few days and consequently the fruit ripens totally over a few days.

In tropical coastal areas particularly those high rainfall areas grapes are not really a well adapted crop. Selected varieties are worthwhile considering for home garden usage in the lower rainfall coastal areas. The gene source of the common grape varieties for the drier sunny areas is Vitis vinifera. Vitus labrusca, the fox grape of eastern USA has some genes which give it a better wet tolerance than V. vinifera. Why fox grape? well it is said to have a foxy flavour but I have never been a fox-eater to now, but I have eaten and enjoyed some V. labrusca varieties, eg. Concord.

As the bunches start to fill, walk along the trellis and pull off about one leaf in ten of those lower leaves that are protecting the fruit. Repeat at about weekly intervals. The increase of sunlight onto the developing fruit gives it SlUl tolerance and the fruit ripen with increased colour and sweetness but no sunburn. The increased sunlight on the developing fruit will add extra colour and sugar as the fruit matures. This extra TLC is only suitable (cost factor) for the home garden situation or for special high quality fruit for special high $/Kg sales.

Ethylene is a natural compound found in most plants where it performs a number of important plant functions such as fruit ripening and stem thickening. In floriculture it induces petal and leaf fall when flowers are carried in mixed consignments that contain apples or bananas which release ethylene as they ripen It is the same chemical compound that is bought in cylinders from industrial gas suppliers to be used in ripening bananas, tomatoes etc.

As of common language usage when we talk about fruit ripening, most of us think that we can pick fruit almost mature and bring it inside and put it on the shelf and wait for it to ripen. Here it is protected from fruit-eating birds and bats but not necessarily from fruit sucking moths (in old Queenslanders). Ripening in this context is that final maturity which will bring the fruit up to full flavour and texture. However not all fruit will ripen after picking. So how do we know which will, and which will not, ripen after harvest, either of their own accord or with a bit of help.

For 'after harvest' ripening to occur, the fruit must have at least some starch in the flesh. In the ripening process the starch is converted into sugars, and at the same time the flesh softens. This is the reverse process to what is happening in the developing fruit where sugars are formed and further converted to starch and laid down in the flesh of the developing fruit to await the ripening signal. Bananas are the best known starch-rich fruit, but also the 'bread fruit' complex, mangoes, rockmelons all have at least some starch and some potential after-harvest ripening.

There are also a lot of fruit with no stored starch. Here we have the pineapples, citrus fruit, water melons, grapes, jaboticaba, carambola etc. How you pick them is how you get them. These fruit store their carbohydrates as sugar. So what's there at the time of picking is what you get But I hear some of you say "but they all change skin colour and it may soften". Yes they change skin colour. They may look more attractive but the flavour has not improved The softening may be there either by natural maturity changes, or if picked very green, by withering.

It is important that all fruit have good sunlight hours in the weeks leading up to harvest It is most important that those "non-starch" fruit get good preharvest sunshine hours to build up the fruit sugars before harvest. Rainy, or cloudy weather gives poor sugar formation, read poor flavour and sweetness. (Carbohydrates = sugars and starches).

A well-drained soil has two components: a gentle slope to run off surface water, and a deep open structure to allow soil moisture to drain freely through the soil profile, giving good aeration. On our wet coastal areas, there are only a few areas that meet these criteria. On the Kairi - Atherton area of the Atherton Tableland, the free-draining red basaltic soils may be up to 24 metres deep, which is very good for avocado growing.

At the height of our wet season with 0.5 metres of rain per month, good drainage and good soil aeration are very hard to come by.

In the wetter coastal areas of Queensland three different fungal rots may infect branches/stems of citrus. These are Pink disease, Fusarium branch rot and Trunk and Root rot. Descriptions of these diseases and suggested control measures can be found in the booklet Citrus in the Home Garden. All three should have preventative measures applied before the onset of the wet season.

a/ Pink disease, when established, often requires infected branches to be pruned out.

b/Fusarium branch rot of the main branches and trunk may kill the tree in one wet season. The infection was probably carried over from a light infection in the previous years wet season.

c/ Trunk Rot can be fairly successfully treated, extending the tree's life.

d/ Root rot should be treated by preventative measures at planting time by using a well-drained soil, or by hilling to give increased drainage. See Citrus in the Home Garden.

A well-drained soil is like the toss of a coin, you either have it in the garden or you don't. Hilling before planting may help overcome this soil-drainage problem.

Literally, insect-eating fungus. In high rainfall areas these fungi can virtually replace the spray program for Beale insect control in citrus. In the high rainfall Daintree valley, the citrus trees only showed small amounts of scale infestation at the end of the dry season. In most years, the fungus was sufficient control. These fungi, when first seen, bring the reaction 'Another fungus to control.' Closer inspection reveals the scale insects with the red (miniature staghorn-like) fungus growing on them. The fungus stands 1-2 mm high. Definitely one of natures goodies.

This statement is a concept only and applies to those Equatorial lowland fruit tree species such as rambutan, durian, mangosteen, breadfruit, cacao. At 16°C, these trees are beginning to show cold damage and at 8°C they are at or very close to severe cold damage - frosting - or death. (Yes, in spite of the heading, frost is still at 0°C.)

Zinc deficiency symptoms show as small leaves - particularly in Hibiscus rosa sinensis cv Snowflake. A foliar spray of zinc sulphate at the rate of 2 grams per litre of water once per year in either early autumn or spring should overcome this problem. Recovery will be seen in the new leaves which form after the treatment. These new leaves may be two to four times as large as the old foliage depending on the level of deficiency.

Zinc deficiency is common in Lychee, Longan, Custard Apples, Rollinia, Sour Sop, Papaw, Cashew, Citrus (all), Cashew, Avocado, and ornamentals such as Hibiscus, Croton, Calliandra (powder puff), Hippeastrum (bent flower stems). Foliar spray with Zinc sulphate at 2 grams per litre of water preferably in spring. Spring - young foliage has better uptake than old foliage. Autumn will do in the first year of treatment. Some uptake is better than none at all. Needs 3-4 days of fine weather after spraying to get full uptake.

Severe deficiency in Custard apples Rollinia, etc. gives very small leaves and terminal stem dieback. In citrus there are small leaves and leaf mottle. In Calliandra there are small leaves and terminal (top outer canopy) stem dieback.

It is generally conceded that banana stains in clothes will not come out. This is not so. Thoroughly wet the stained garment. Then pour on enough KEMDEX (denture stain powder) to put a layer of powder over the stained area and lightly rub in to the cloth. Then roll up the garment and leave for 3-4 days. You may need to pour on some more water to keep the garment wet. If the stain is persistent, you may need to rewet and sprinkle on some more powder and leave for a few more days. When stain has gone, rinse well and hang garment out to dry. Don't use the pink denture powder as it may stain. Useful on other stains, eg Biro.

Leaf and fruit cooling depends on water picked up by the roots and translocated to the leaves/fruit. Any particular segment of the canopy receives its water from the roots under that segment of canopy. Symptoms are brown scalded areas in those leaf parts that face directly into the early afternoon sun. Not really much of a problem when the tree is only carrying leaves. It is, however, very important in summer when the tree is carrying fruit, particularly young fruit. May cause fruit drop.

Control is to set the sprinklers so as to fully irrigate the northwest quadrant of the root system to out past the dripline. If there is to be a rain shadow, let it be in the south east quadrant of the root system.

A.J. (Jim) Wait

DATE: August 1999

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