Flower development and factors affecting the blooming time of Tabebuia rosea (Bertol.) DC.

Pink trumpet tree (Tabebuia rosea (Bertol.) DC.) is a native Central American tropical tree. The full bloom period is from late January to April. Their blooming pattern gives a spectacular pink scenery resembling the cherry blossom in the temperate region. A forecast for blooming period is important for the tourism industry. However, climate change has made it difficult to predict the blooming time. By using meteorological data and photographic evidence of the past nine years, it was found that flower buds were already formed at the beginning of the dry season. The blooming of T. rosea depended on the time of in-season rainfall ended. It also required a certain continuous dry period, believed to be approximately 60 days, depending on the rate of water evaporation. The blooming time counting from the last in-season rainfall would be early when the rainy season ended early and also when the dry period had a high evaporation rate. If the first 60 days of the dry period was interrupted by off-season rainfall of at least 10 mm, the blooming time would be delayed. But if the rain was after 60 days, the spectacular mass blooming in leafless trees could be expected in 23 days. To prove the effect of dry period interruption on blooming time, irrigation of 30 mm to the tree was conducted. The result showed that the blooming time could be delayed or enhanced, depending on the stage of the flower buds during the raining or irrigating period. Based on these results, to predict the blooming date, one must consider the time of rainy season ending, the time of the off-season rainfall of at least 10 mm in combination with the evaporation rate during the dry period, and the stage of the flower bud development at the prediction time.