Use of rock dust in Verbena × hybrida propagation for landscape use

Contemporary landscaping requires the use of sustainable techniques which do not pollute the urban environment. Basalt is a local rock abundant in the south of Brazil. Moreover, since it provides for slow release, it may be used as a soil conditioner in landscaping projects or in the mixture of local substrates used in ornamental plant propagation. Verbena × hybrida is a perennial and ruderal plant, which is widely used in landscaping resulting in low care needs such as fertilization, irrigation and pruning. This study deals with current questions in regard to the qualities of this material and its application in landscaping illustrated through a test of propagation of cuttings of Verbena × hybrida in hand-crafted organic substrates with the addition of basaltic rock powder (65 mesh particle size at 6% of the volume of the substrate). In the first evaluation, 54 days after setting up the test, no significant effect was observed in the use of basalt rock dust in the process of root formation, but sprouting was enhanced. This may be explained in this short period through the fact of this rock dust releasing nutrients slowly, and the process of using cuttings requires immediate physiological changes in the cells which give rise to adventitious roots. Even though results were not significant, the use of rock dust reduced the survival of the cuttings and improved some aerial morphological parameters.