Environmental conditions play an important role in determining the flowering and fruiting of guava. In particular, periods of water stress are critical to enhance flowering. Also, full sunlight is required for efficient flowering and fruiting. Often under favourable conditions many white flowers either solitary or in groups of two or three arising from the leaf axils of young shoots and abundant fruits can be seen on guava trees. The guava bears solitary flowers or in a cyme of two to three flowers on the current season's growth, in the axils of the leaves. Normally, the bearing twigs grow a few centimetres long, putting our 4 or 5 leaves. If the flower sets, the terminal bud ceases to grow until the next growing season. The flowering bud is a mixed type and the flowering shoots bear the flower laterally. The axillary buds are not produced all over the shoot and may appear scattered. The flowering or blooming period varies from 25 to 45 days depending on the variety , season and region of growing.
Guavas are primarily self-pollinated, although some strains seem to produce more fruits when cross-pollinated with another variety . The chief pollinator of guavas is the honeybee. The initial fruit set in nature is quite high, 80-86% of the flowers set fruit. However, due to severe fruit drop, only 34 to 56 % of the fruits reach maturity. In seedless clones, the final retention is as low as 6%. The fruit drop may be due to different physiological and environmental factors. The formation of fruit is first noticed 12 days after flowering. Normally the guava fruit takes about 15 to 17 weeks from fruit set to harvest.
Fruit set and yield increases with the treatment of Gibberellic Acid (GA) at 15 or 30 ppm. Treating guava trees with GA at 200 ppm retains 90% of fruit. The fruits produced will be less susceptible to fruit drop, bigger, have less seeds and improved quality characters such as TSS and ascorbic acid. When still unopened, the flower buds are weakened and the styles cut off. A GA-lanolin mixture is applied to the cut surface and seedless fruit will be produced. Fruit obtained by this treatment are larger than untreated fruit but do have 6 to 8 prominent ridges and swelling at the calyx end.
Guava trees that are propagated by budding or grafting will normally bear fruits in 1 to 2 years while trees grown from seeds may take up to 2 or 3 years before reaching bearing stage. The maturity period may also vary substantially among different seeded varieties. For example, the Taiwan variety takes 20 weeks from fruit-set to full maturity while the Kampuchea variety takes 16 weeks to mature. In general, yield in the first year of bearing is low but this increases rapidly to reach up to 40 to 50 t/ha within 4 to 5 years of planting. |
Fruits produced during the rainy season are rather bland and watery and do not keep well.To get good yields, withhold water and remove the soil around the upper roots and cover with an oil and organic mixture. Two light irrigations are also recommended rather than one heavy one.
Growth regulators have been found to be very effective in thinning flowers and manipulating the cropping season. Chemicals found to be effective chemicals are NAA (1-Naphthaleneacetic Acid), NAD (1-Naphthaleneacetamide) and 2,4-D. Spraying with NAA at 100 ppm reduces the cropping season considerably, but the best results are obtained by hand-thinning the flowers. This reduces the rainy season crop by 80% and increases the following crops by over 180%.
NAA at 80 or 100 ppm greatly reduces the fruit set of guava when sprayed in certain months and is recommended as an alternative to the conventional method of withholding water before flowering.
The most effective thinning the flowers is by the use of NAD at 50 ppm or 2,4-D at 30 ppm. By thinning the flowers, an increase in yield by 200-300% can be obtained. |
