Abstract

The aqueous extract of Salix spp contains many compounds which may act as root-promoting agents in cuttings. S. alba is a deciduous tree, phytochemicals and hormones in deciduous trees are variable throughout the year. So, in this study, one- and two-year-old shoots of S. alba were collected on the 15^th of each month in the year 2022, extracted in 2% ethanol at 9 g.L^-1, and placed in a water bath at 35 °C, then they applied to thornless blackberry cuttings for 1.5 h. The results explained that the highest rooting percentage (66.66%) was obtained in the cuttings soaked in the extract of willow shoots collected on 15^th of January. They were not significantly different from control cuttings, but they were different from the cuttings soaked in the extract of willow shoots collected on 15^th of August and October (33.33%). The majority of other shoot and root traits were high in the cuttings soaked in the extract of willow shoots collected on 15^th of December. The willow shoots collected on 15^th of January contained the lowest total phenols (51.4 µg. mL^-1) and total flavonoids (29.07 µg. mL^-1).  Moreover, the highest total phenols (57 µg. mL^-1), SA (492.61 µg. mL^-1), and IAA (365.17 µg. mL^-1) were recorded in the willow shoots collected on 15^th of March, and total flavonoids were the highest (44.96 µg. mL^-1) in the willow shoots collected on 15^th of April. Generally, based on rooting percentage, it is advisable to collect willow shoots on 15^th of January and February for extract and application to the thornless blackberry cuttings.