Promotion of Terminalia brownii in Reforestation by Development of Appropriate Dormancy Breaking and Germination Methods in Drylands; Kenya



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Terminalia brownii Fresen in the Combretaceae family, is one of the indigenous tree species used in agroforestry, afforestation and reforestation programmes in drylands of Kenya. It is widely distributed in the semi-arid lands of East, Central and West Africa. It is an important drought tolerant and multipurpose agroforestry species whose potential is underutilized due to poor seed germination. Its products such as timbers, posts, charcoal and curving wood among others are not available in required quantities for domestic and industrial use. Exploitation of T. brownii is on the increase, but efforts to promote its planting are thwarted by lack of seedlings attributed to poor seed germination. This study investigated dormancy and germination of T. brownii seeds. Mature T. brownii fruits were harvested from Ikanga, Mbumbuni, Kabururu and Kimose sites; in Kitui, Makueni, Tharaka Nithi and Baringo counties of Kenya respectively. Flowering and fruiting was monitored and mature fruits harvested for dormancy and germination tests. To conduct germination tests, one hundred fruits and extracted seeds were subjected to each of the following treatments: mature whole fruits (control), dewinged fruits, fruits nipped at the distal and proximal ends and extracted seeds in four replicates. Extracted seeds started germinating after incubation for 7 days, while fruits nipped at the distal end took 21 days. The control and all other treatments from all sites failed to germinate after an incubation period of 60 days. Extracted T. brownii seeds recorded the highest germination with the best at 76% from Ikanga, while those nipped at the distal ends recorded a mean germination of 13% across all sites. There is evidence suggesting that T. brownii fruits recorded poor germination due physiological seed dormancy probably imposed by the hard samara fruit. These findings suggest that T. brownii fruits from Kimose should be nipped at the distal end, while those from Eastern Kenya (Kitui and Makueni Counties) should be extracted completely by removing the seed from the fruit to enhance germination. These results will inform choice of propagation of T. brownii seeds and enhance its planting in various agroforestry practices and afforestation programmes.