Rooting and vegetative propagation in Laguncularia racemosa

Reproduction and dispersal in mangrove species occurs mainly through propagules. Vegetative propagation is considered to be insignificant by many researchers, however, for restoration projects, it could be an important advantage. Therefore, we carried out experiments with shoot cuttings of Laguncularia racemosa and Rhizophora mangle under controlled conditions as well as in the field to prove the feasibility of vegetative propagation in these mangrove species. None of 110 planted R. mangle cuttings survived the experiments, but the results with L. racemosa were promising. We observed that the single most important factor for survival of L. racemosa cuttings was rooting of the shoots prior to cutting from the parent trees. This is a common feature in the study area, the Cienaga Grande de Santa Marta, Colombia. Seasonal floodings of lower branches induce secondary root growth and can even lead to natural vegetative propagation. Other factors that have favorable effects on the survival of the cuttings are a large shoot diameter, manual defoliation to reduce transpiration, and direct sun irradiation. Additionally, burying a small part of the roots in a way that allows some roots to freely float in the surface water, improves the survival rate to 95%. However, the watering with rooting agents shows slightly negative effects. The surviving shoots grow rapidly and fruit set can be observed within six months after planting in the field. In restoration attempts with L. racemosa it is, therefore, possible to bypass the very sensitive seedling phase by planting shoot cuttings. The value of this method is linked to quicker establishment and reproduction of the cuttings as well as the possibility to plant them in flooded areas, where establishment of propagules and survival of seedlings of L. racemosa is very difficult to achieve. (C) 1999 Elsevier Science B.V. All rights reserved.