The mandarin orange, Citrus reticulata, is in greatest demand during the Chinese New Year when they are served to guests and given away as presents. This custom is particularly strong among ethnic Chinese in Malaysia and Singapore. Mandarin oranges are imported from China. They grow in Malaysia but fruit irregularly and local fruits are considered inferior. In China, they fruit at the right time. Since the date for the Chinese New Year follows the lunar calendar and is out of synch with the solar calendar, and since plant behaviour is believed to follow the solar calendar, I have never understood how mandarin oranges in China 'know' when it is time to ripen.
Another Citrus associated with Chinese New Year in Malaysia and Singapore is the locally grown Citrus microcarpa (known as limau kasturi in Malay and calamondin in the Philippines). The plants flower and fruits irregularly throughout the year, but nurserymen have learnt to manage them so that they flower before the festival and fruits ripen just at the right time. The plants, heavily laden with fruits, are used to as decorations. Most years, the growers get the timing right, but this year is disastrous. I hear that the price for plants has doubled compared to last year because of very poor fruiting. This is blamed on the exceptionally wet weather. It has been raining every day for over a month and there has been serious flooding in many parts of the region.
I have a plant that is growing vigorously in my garden, flowering and fruiting profusely and totally unaffected by the wet weather. It grows in a pot of horticultural carbon. All the excess water simply drains off. Improved drainage may be what the plants need most in wet weather.