Rooting and vegetative propagation in Laguncularia racemosa

Reproduction and dispersal in mangrove species occurs mainly through propag ules. Vegetative propagation is considered to be insignificant by many rese archers, however, for restoration projects, it could be an important advant age. Therefore, we carried out experiments with shoot cuttings of Laguncula ria racemosa and Rhizophora mangle under controlled conditions as well as i n the field to prove the feasibility of vegetative propagation in these man grove species. None of 110 planted R. mangle cuttings survived the experiments, but the re sults with L. racemosa were promising. We observed that the single most imp ortant factor for survival of L. racemosa cuttings was rooting of the shoot s prior to cutting from the parent trees. This is a common feature in the s tudy 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 s urvival of the cuttings are a large shoot diameter, manual defoliation to r educe transpiration, and direct sun irradiation. Additionally, burying a sm all part of the roots in a way that allows some roots to freely float in th e surface water, improves the survival rate to 95%. However, the watering w ith rooting agents shows slightly negative effects. The surviving shoots gr ow rapidly and fruit set can be observed within six months after planting i n the field. In restoration attempts with L. racemosa it is, therefore, possible to bypa ss the very sensitive seedling phase by planting shoot cuttings. The value of this method is linked to quicker establishment and reproduction of the c uttings as well as the possibility to plant them in flooded areas, where es tablishment of propagules and survival of seedlings of L. racemosa is very difficult to achieve. (C) 1999 Elsevier Science B.V. All rights reserved.