LITCHI AND LONGAN - Tropical Fruits - page 224

Litchi

Temperature > 25 ° C Temperature < 25 ° C Temperature 15 ° C

Infloresence
with flowers
only

High water, high N Low water and N Temperature < 25 ° C 10 weeks

Floral Induction
and development

Harvest Leaf Growth Rest

Infloresences
with one or more
leaves or revision
to vegetative shoot

Pruning
old panicle removal
fertilize and Irrigate

Girdling
Remove vegetative shoots

Irrigate Temperature > 15 ° C

or < 10 weeks

Longan

Temperature 15-22 ° C

Temperature > 25 ° C Temperature C

Low water and N, or sodium chlorate

< 25 °

High water, high N 8-10 weeks

Flowering

Floral Induction
and development

Harvest Leaf growth Rest

No flowering

Fertilize
Irrigate

Irrigate Temperature > 22 ° C

or < 8 weeks

Fig. 9.1. Fruiting cycle of litchi (after Menzel and Simpson, 1994) and longan as
affected by temperature, nitrogen fertilization and water availability. Litchi leaf low
nitrogen levels need to be in the range of 1.75-1.8%. There can be more than one
fl ush of leaf growth during the year. Longan can be induced to fl ower with a sodium
chlorate treatment.

fl owering (Fig. 9.1), even though the tree fl owers profusely in areas with high
water tables. Both crops require adequate moisture, from rainfall or irrigation,
during fruit set and growth.

Temperature
Young litchi and longan trees are severely damaged or even killed at − 2
to − 3°C, with dormant and mature trees having more tolerance to low
temperatures. Periodic cold is required for fl owering, though in Guangzhou,
air temperatures rarely drop below 0°C. The total duration of relatively low
temperatures rather than the frequency or time of occurrence during a critical
period seems to be the determining factor (Fig. 9.1). When trees are deeply
rooted, low air temperature is more important than soil moisture (Menzel et
al. , 1989). There is considerable cultivar dif erence in response to temperature
(Menzel et al. , 1989). In a test involving seven cultivars, all cultivars showed
panicle emergence after 6 weeks at 15/10°C or at 20/15°C; however, there
are dif erences in the degrees of fl owering between the cultivars at 20/15°C
(Table 9.1). There is no fl owering at 25/20°C or 30/25°C. Temperature also
infl uences the time from emergence to anthesis: 14-16 weeks at 20/15°C,
versus 6-8 weeks at 15/10°C. The greatest number of infl orescences
per branch occurs if low temperatures are maintained until anthesis. If
temperatures are increased from varying the period at 15/10°C to 30/25°C
after emergence and before anthesis, there is a reduced number of female
fl owers and some fl oral buds revert to vegetative growth (Fig. 9.2). Pollination
is optimum at about 19-22°C and occurs in 5-7 days. At lower temperatures,