Flowering Habits of
in the Tropics
Story and Photos by Pairat Songpanich,
Edited and Translated by Dr. Slearmlarp Wasuwat, Thailand
Graphic illustration in Figure 2 demonstrates an outstanding
performance in flowering by Nymphaea 'Gloriosa' at 163
blooms per year. Next were N. 'Charles de Meurville',
N. 'Sirius' and N. 'Peachglow' produced 127, 116
and 114 blooms respectively. The lowest were N. 'Perry's
Fire Opal', N. 'Sanguinea', N. 'Sunrise', N.
'Gonnère', N. 'Yuh Ling', and N. 'Colorado'
which bloomed 28, 28, 30, 33 and 36 respectively. It should be
noted here that N. 'Gloriosa' produced flowers nine times
more than N. 'Perry's Fire Opal'.
Average number of flowers produced by 21 cultivars was 73
blooms/cultivar/year. Nine cultivars produced blooms at higher
than average value; the other 12 cultivars were lower.
< N. 'Perry's Fire Opal'
Figure 2. One year flowering
performance of hardy waterlily in the tropics
Graphic illustration in Figure 3 shows that the pattern of
flower production of all cultivars varied in similar directions.
Each year and on the average, flower production was only a little
early in the year and gradually increased until April. They increased
slightly during April and May, then increased to their peak in
July. The flowering then gradually dropped to their lowest at
the end of the year.
Figure 3. Flower production
in 2001-2003 and their averages
Graphics presented in Figure 4 indicate a positive correlation
of flowering production and day length (number of hours between
sunrise and sunset). Even though the latitude at the studied
location area was 13° 51' 40" North, the longest day
in June was 12.80 hours and the shortest day length in December
was 11.20 hours. The difference was only 1.60 hours. Note the
highest flower production of 266 in July compared to the lowest
of 18 flowers in January. Both results were about one month after
the highest and lowest of day length peak. It can be confirmed
that day length is one of the major factors influencing flowering
production of hardy waterlilies when grown in the tropics.
Figure 4. Correlation
of day length and flower production of hardy waterlilies in the
Looking back at Table 1, one may notice some cultivars
were very sensitive, some partially sensitive to short day length.
1. Very sensitive to short day length at the early and the
end of the year such as N. 'Gonnère', N.
'Perry's Fire Opal', N. 'Pink Sensation, and N.
2. Partially sensitive such as N. 'Gloriosa', N.
'Gypsy' and N. 'Colorado'
Temperature was the second factor affecting flowering of hardy
waterlilies, next to day length. Extreme hot or cold climate
would reduce flower production.
The monthly temperature averages over three years during the
studies and average of monthly flowering in Figure 5 shows the
influence of temperature. Rate of flower production was reduced
for one to two months from May to June after very hot temperatures
in April. Also, flowers were few, even more so, during very cold
[for Thailand] weather in December and January. Some cultivars
rested and dropped their floating leaves. Thus, one can conclude
that day length and temperature are two factors influencing flower
production of hardy waterlilies grown in the tropics.
Figure 5. Influence of temperature
on flowering of hardy waterlilies grown in the tropics
There were no outstanding effects of daily duration of sunlight
(Figure 6), and relative humidity (Figure 7).
Figure 6. Relation of sunlight
and flowering of hardy waterlilies in the tropics
Figure 7. Relation of relative
humidity and flowering of hardy waterlilies in the tropics
Besides good care and maintenance of hardy waterlilies in
a tropical climate, for best production of flowers, day length
and temperature are two major factors. Long day length increases
flowering and vise-versa. Cold climate that affects growth of
most plants makes a more pronounced effect on hardy waterlilies
when grown in tropical areas.
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