Stock Plant Management of Lavandula angustifolia ‘Wee One' Using Plant Growth Regulators

Abstract

Lavandula angustifolia ‘Wee One' is a drought-tolerant perennial being used in landscapes throughout the western United States. Increased demand has resulted in problems with stock plant management and propagation due to the relatively small and slow vegetative growth. The objective was to determine if gibberellic acid, benzyladenine, ethephon, or auxin [indole-3-butyric acid (IBA)] plant growth regulators (PGR) applied as a foliar spray on Wee One lavender plants could be used to increase the number of cuttings for production. Fifteen replications of Wee One Lavender were evaluated for four months for plant height, width, number of cuttings, and fresh and dry weight of the cuttings. This study was replicated twice, the first experiment was performed from March 2020 to July 2020 and the second experiment from August 2020 to December 2020. A secondary propagation study was conducted simultaneously to check if PGR residuals effected rooting. The use of different PGRs caused an increase of cuttings from stock plants throughout both experiments. Foliar applications of gibberellin (ProGibb T&O) at 100 mg·L−1 (ppm) increased stem length and branching in one experiment, resulting in a higher number of cuttings produced compared to nontreated control stock plants, although that effect was not seen in the other conducted study. In one study, ProGibb T&O application did not negatively impact the rooting of individual cuttings, while it did so in the other study. Species used in this study: Wee One lavender [Lavandula angustifolia Mill]. Chemicals used in this study: gibberellic acid (GA3), ethephon, indole-3-butyric acid(IBA), N-(phenylmethyl)-IH-purine 6-amine (BA).