Grafting between species of the genus Handroanthus for the production of multi-colored flower canopies

Urban afforestation is done with trees with adequate size for streets, squares and avenues, as well as those with showy canopies. Trees of the genus Handroanthus and belonging to the family Bignoniaceae are widely used due to their canopies flowering in different colors used for landscape purposes. The use of techniques such as grafting, which assist in early flowering and the possibility of canopies producing flowers of different colors can be of importance. This study aimed to analyze the grafting compatibility in bifurcated seedlings of the genus Handroanthus for the production of multi-colored flowering canopies. The experiment was constituted by 10 treatments, with different scion/rootstock combinations. The studied species were Handroanthus heptaphyllus (Hh), Handroanthus impetiginosus (Hi), Handroanthus chrysotrichus (Hc), and Handronthus roseo-albus (Hr-a), using Hi as the only rootstock species (via seeds), and the remaining species, including Hi from adult plants as scions. Single-stem wedge grafting on a bifurcated seedling was adopted for the following combinations: 1. Hc/Hi; 2. Hr-a/Hi; 3. Hh/Hi; 4. Hi/Hi, whereas double-stem wedge grafting was adopted for: 5. Hi/Hi and Hc/Hi; 6. Hi/Hi and Hr-a/Hi; 7. Hi/Hi and Hh/Hi; 8. Hc/Hi and Hr-a/Hi; 9. Hc/Hi and Hh/Hi; and 10. Hr-a/Hi and Hh/Hi), with three replications of five seedlings. The take percentage and vigor were evaluated 50 days after grafting. The highest establishment rates for the single-stem wedge grafting were obtained by the same species grafts Hi/Hi (80%) and by the Hr-a/Hi (86.6%) combination; whereas for the double-stem grafting the following percentages of combinations were obtained: Hc/Hi (93.3%) and Hr-a/Hi (93.3%); Hc/Hi (73.3%) and Hh/Hi (86.6%); and Hr-a/Hi (86.6%) and Hh/Hi (86.6%).