The recent study, carried out in 2022 in Bismayah City, Baghdad, Iraq, aimed to investigate the influence of humic and salicylic acids on the growth traits of different trees. The first factor was humic acid (H) with three levels – water spray (H₀ control), 5 g L^-1 (H₁), and 10 g L^-1 (H₂). The second factor was salicylic acid with three levels, i.e., water spray (S₀ control), 250 mg L^-1 (S₁), and 500 mg L^-1 (S₂). The third factor was four tree types, namely, Eucalyptus camaldulensis L. (T₁), Albizia lebbeck L. (T₂), Ficus carica L. (T₃), and Morus nigra L. (T₄). The study comprised a randomized complete block design with three replications. The results showed that humic acid, 10 g L^-1 (H₂), significantly increased the stem diameter (28.20 mm), plant height (36.50 cm), shoot length (37.64 cm), and leaf chlorophyll content (29.45 mg g^-1). The salicylic acid spray of 500 mg L^-1 (S₂) significantly enhanced the plant height (32.59 cm), shoot length (36.82 cm), and leaf chlorophyll content (28.22 mg g^-1). Albizia lebbeck L. (T₂) excelled with an enhanced stem diameter (34.54 mm) and plant height (46.77 cm). Eucalyptus camaldulensis L. (T₁) was superior with an extended shoot length (43.64 cm). However, Ficus carica L. (T₃) was superb in the leaf chlorophyll content (29.51 mg g-1). The interactions among the study factors significantly affected all the studied vegetative growth traits.

Keywords: Humic acid, salicylic acid, phytoremediation, transplants, plant height, foliar application

Key findings: The studied traits significantly increased especially when sprayed with humic acid at 10 g L^-1 and salicylic acid at 500 mg L^-1. Moreover, the transplants varied among themselves in vegetative growth characteristics.