Abstract
This pape, reports some observations on flowering of Tabebuia pentaphylla (L.) Hemsl. in four difierent localities of the Central Valley of Costa Rica.
Flowering began earlier at the lowest site (Villa Colón, 800 m) and here also reached its highest percentage. On the other hand, flowe,ing was late and relatively scanty in San Pedro de Montes de Oca (1220 ID), a site where trees kept a high percentage of the foliage. Shading and a high level of soil moisture seem te be local factors affecting flowering adversely, whereas temperature is apparently responsible for differences along an altitudinal gradient. It is very likely Ihat high temperatures increase substantially the rate of evapotranspiration in lower sites, reducing soil moisture to a level that favors leaf fall and the development of water stress in the plants, factors that promote flowering. It is also possible, that relatively low temperatures at higher localities reduce the rate of photosynthesis. This would explain, partially, the lower percentage of flowering at San Pedro de Montes de Oca.
The breaking of dormancy of vegetative buds started also first at the lowest site, but here and at the other places, it took place in or after March, the month that disphys the greatest diurnal temperature oscillation of the flowering period.