Effects of nutrition and paclobutrazol on container-grown godetia (Clarkia amoena): A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Horticultural Science (Honours) at Lincoln University

Abstract

Seedlings of Clarkia amoena 'Grace Lavender' were grown in a peat:sand (v:v) media to evaluate their response to 5 levels of nitrogen (N), phosphorus (P), and potassium (K). C. amoena was shown to have a low fertility requirement, particularly with regard to N, for the production of high quality cut flowers. Strong growth responses were shown to added N including increases in plant height, lateral number, flower number and plant dry weight. Plant quality for cut flower production declined with added N as a result of weakened stems and an increase in branching near the terminal flowers. A recommended rate of N fertiliser of 275 g Nm⁻³, equivalent to 50 g N m⁻³ month⁻¹, was made which was produced highest yields with minimal reduction in quality. There were fewer P and K responses than to N and consequently there were few interactions. Recommended optimum rates of P and K were 200 g P m⁻³, equivalent to 36 g P m⁻³ month⁻¹, and 330 g K m⁻³, equivalent to 60 g K m⁻³ month. In a second experiment C. amoena seedlings were grown in the same media with paclobutrazol applied as a 100 ml media drench at concentrations of 0, 10, and 100 ppm, N at rates of 110, 330, 550, and 770 g m⁻³, K at rates of 0 and 60 g m⁻³ to evaluate growth retardant and nutrition effects on pot plant production. Paclobutrazol applied at 100 ppm reduced plant sufficiently to produce plants of suitable size as pot plants. High rates of plant death occurred at high concentrations of paclobutrazol. There was no clear optimum nutrition level for growth retarded plants. Negative responses to nil rates of K were shown only when the N status of the plants was high.