Restricting Phosphorous Can Manage Growth and Development of Containerized Sweet Basil, Dill, Parsley, and Sage

Abstract

The objective of this research was to quantify the effects of phosphorous (P) concentrations on the growth, development, and tissue mineral nutrient concentrations of four popular culinary herbs commonly grown in containers. Seedlings of sweet basil (Ocimum basilicum ‘Italian Large Leaf’), dill (Anethum graveolens ‘Fernleaf’), parsley (Petroselinum crispum ‘Giant of Italy’), and sage (Salvia officinalis) were individually transplanted to 11.4-cm-diameter containers filled with soilless substrate comprising canadian sphagnum peatmoss and coarse perlite. Upon transplanting and throughout the experiment, seedlings were irrigated with solutions containing 0, 5, 10, 20, or 40 mg·L−1 P; all other macro- and micronutrient concentrations were the same across P concentrations. Plants were grown for 4 weeks in a greenhouse; after that time, data were collected. Relationships between height and width and P concentrations were nonlinear for all four species; height and width increased as P increased to more than 0 mg·L−1 until the species-specific maxima; after that time, no further increase occurred. The same trend was observed for the branch length of sweet basil and sage, and for internode length, leaf area, and shoot dry mass of all four species. Although visible P deficiency symptoms were observed for plants provided with 0 mg·L−1 P, there were no signs of P deficiency for plants provided with ≥5 mg·L−1 P, even though tissue P concentrations were below the recommended sufficiency ranges. As a result of this research, containerized sweet basil, dill, parsley, and sage can be provided with 5 to 10 mg·L−1 P during production to limit growth and produce plants without visible nutrient deficiency symptoms that are proportional to their containers.