Cuttings of Aloysia citriodora Palau: greenhouse trials under different rooting conditions

Abstract

Aloysia citriodora Palau, Verbenaceae, known as lemon verbena, is one of the most cultivated and marketed medicinal and aromatic plants in Portugal. Biomass quality and uniformity of the plant material according to stakeholders standards are market criteria requiring important amounts of biomass supplied by producers organic fields. However, in order to satisfy such biomass needs, horticulturists should provide vegetative propagated plant material to install new fields or to regenerate the existing ones. Producing cuttings depends on the availability of plant material throughout the year and on rooting processes which could not be easy to induce.

Woody and softwood stem cuttings were prepared from plants grown in the field. Different substrates, thickness of propagated material and exogenous application of auxin were compared in their capability to induce root and shoot formation. In other experiment, the rhizogenic ability of plant material was monthly assessed for a year from plants grown in a greenhouse.

Cuttings placed in perlite presented higher percentages of rooting than those in organic substrate, although in both cases values of root formation were always below 20%. Organic substrate combined with thick cuttings and absence of nebulization had a better performance than thin cuttings with nebulization. Throughout the year, the rooting percentages were highest in May, with values greater than 70%. The softwood cuttings from summer period originated particularly low rooting percentages