Response of vegetative and flowering growth indicators to planting distances and spraying with plant extracts in Solidago Canadensis

Abstract

A field experiment was conducted at Research Station A, College of Agricultural Engineering Sciences, University of Baghdad, during the 2024–2025 growing
season to evaluate the effects of plant density and foliar application of coconut and lemongrass extracts on the vegetative growth and flowering performance of
Solidago sp. Uniform saplings, each approximately 10 cm in height, were obtained from a private nursery in Wasit Governorate on 12 February 2025 and
transplanted to the permanent field on 15 February 2025. The experiment was arranged as a factorial trial within a randomized complete block design using a splitplot arrangement, with three replicates and six plants per experimental unit, resulting in a total of 45 experimental units. The main plots consisted of three planting
distances: 50, 75, and 100 cm. The subplots included five foliar treatments: coconut extract at 100 and 50 ml L-1
, lemongrass extract at 50 and 25 ml L-1
, and an
untreated control. The results revealed that planting distance significantly affected most vegetative and flowering characteristics. The 100 cm spacing produced
the highest leaf area and improved Fe and Mn contents, whereas the 75 cm spacing enhanced Zn concentration. With respect to flowering traits, the widest spacing
increased flower number, flower stalk diameter, and flower retention period, while the intermediate spacing improved flower stalk length, reduced the time to
flowering, and extended flowering life. Among the foliar treatments, lemongrass extract was the most effective in enhancing most vegetative and flowering
parameters, including leaf area, micronutrient content, flower number, flower stalk length, retention period, and flowering life. Coconut extract was superior in
improving flower stalk diameter. The interaction between planting distance and plant extracts significantly enhanced most measured traits.