Cutting propagation of foliage crops using a foliar application of auxin

Abstract

Rooting and initial shoot growth was evaluated on stem cuttings of four tropical ornamentals receiving no auxin treatment, a basal quick-dip in auxin (4920 μM IBA + 2685 μM NAA) prior to insertion into the rooting substrate, or a spray-to-drip foliar application of auxin (ranging from 4.9 μM IBA + 2.7 μM NAA to 492 μM IBA + 269 μM NAA) after insertion into the rooting substrate. Terminal cuttings of Aglaonema modestum Schott ex Engler treated with the basal quick-dip produced 9.5 roots per cutting and total root length of 386 mm, while untreated cuttings produced 6.1 roots per cutting and total root length of 270 mm; auxin spray treatments gave intermediate results. Two-node cuttings of Gardenia augusta (L.) Merrill ‘Radicans’ ( Gardenia jasminoides Ellis ‘Radicans’) treated with the basal quick-dip produced 9.1 roots per cutting and total root length of 311 mm, untreated and sprayed cuttings produced similar or lesser results (as low as 5.2 roots per cutting and total root length of 66 mm for untreated cuttings). Total root length on terminal cuttings of Ficus benjamina L. was 332 mm when untreated, 400 mm when treated with a basal quick-dip, and 280–355 mm when sprayed with auxin at rates of 49.2 μM IBA + 26.9 μM NAA or higher; auxin sprays at lower rates produced lesser total root length (189–218 mm) than the basal quick-dip. Medial cuttings of Hedera helix L. ‘Ivalace’ treated with the basal quick-dip produced 8.3 roots per cutting and total root length of 257 mm; untreated cuttings and sprayed cuttings produced similar results. Subsequent shoot or foliage development on cuttings of all species receiving the spray treatments was similar in most cases to cuttings receiving no auxin treatment or a basal quick-dip treatment.