Vegetative propagation of Colutea arborescens L., a multipurpose leguminous shrub of semiarid climates

The vegetative propagation of the multipurpose leguminous shrub Colutea arb orescens from leafless hardwood cuttings was examined. Specific attention w as paid to the factors: 1) cutting origin (apical, medial or basal); 2) ind ole-3-butyric acid (IBA) treatment (0, 50 or 200 ppm); and 3) relative humi dity of the propagation environment (high or low humidity). After 120 days, 67.6% of the C. arborescens cuttings had rooted. The rooting ability of th e cuttings was significantly influenced by the cutting origin and hormonal treatment. No effects on rooting percentage were shown by the relative humi dity of the propagation environment. The best rooting response (95%) was sh own by basal cuttings treated with 200 ppm IBA. Cutting origin, IBA treatme nt and relative humidity were significantly related to the root number, lon gest root length and the fresh/dry biomass of roots and leaves. Under condi tions of high humidity, basal cuttings treated with 200 ppm IBA gave rise t o the most highly developed plants. The positive relationship between sprou ting and rooting suggests that successful propagation is related to the sho ot formation potential of the cutting's food reserves. These findings were used to propose an efficient method for the vegetative propagation of C. ar borescens plants.