Abstract

For the first time, natural seed germination in cultivated population of Cassia fistula Linn. is reported in this paper. Natural seed germination occurred under many mother trees at Covenant University, Ota, Ogun State, Nigeria; while no germination occurred under some other mother trees. Random soil samples were taken in representative areas and analysed. Seedling dynamics were also investigated by fencing the seedlings around five mother trees, mapping and following their survival with time. Soil samples obtained where there was germination are loose, black soils with high moisture and humus contents and mean pH of 7.2 while soil samples obtained where there was no germination are hard, red lateritic clay soils with significantly lower moisture and humus contents and mean pH of 6.4. The seedlings study showed that some seedlings were more or less in a straight line from broken and rotted pods buried in the soil or covered in debris. Other seedlings were single, in pairs or in groups of three or four. A seed germinated within a pod and grew out of a small hole in the pod, with the radicle coming out first and by the next day, the cotyledons emerged. In the first few weeks of study, the number of seedlings in each fenced area increased with time, thereafter the number decreased accompanied by yellowing of leaves. There was also increased growth of surrounding weeds mainly grasses, as well as about 60% reduction in light intensity on the seedling floor due to the development of new foliage on the mother trees. The reduced number of seedlings under the mother trees was attributed to increased inter specific competition as well as reduced light intensity reaching the seedlings since C. fistula is not shade tolerant. Consequently, cultivated C. fistula like the natural population may not regenerate well in nature and its continued existence may depend on artificial conservation through its use as ornamental and medicinal plant.

Key words: Natural germination, seedling dynamics, cultivated population, Cassia fistula, Nigeria.