Coleus Cultivars Nutritional Status As a Function of Leaf Coloration

Sixteen coleus (Coleus scutellarioides) cultivars (genotypes) with four cultivars representing four industry-categorized color groups [phenotypes (Burgundy, Orange, Red, and Yellow/Green)] were evaluated to determine if leaf color affected tissue nutrient concentrations. Plants were grown at two locations provided with a liquid fertilizer concentration of 150 mg.L-1 N delivered from 17 N-1.31P-14.1K. Leaf tissue samples were collected and analyzed for the concentration of 12 elemental nutrients after eight or 10 wk of growth, depending on location. Leaf tissue nutrient concentrations were influenced by leaf color (color groups), but the magnitude varied for each elemental nutrient. Leaf tissue nutrient concentrations were significantly different for each color group for phorphorus (P), potassium (K), calcium, magnesium, iron, copper and boron, but not for nitrogen, sulfur, manganese, or zinc. Trends for higher P and K leaf tissue concentrations in Red-leaf coleus cultivars, and lower P in Yellow/Green cultivars agree with prior work reported for Heuchera sp. This data further support the initial foundational work to determine the relationship between leaf color and tissue nutrient concentration. Further investigations among other species may offer additional data that will help establish a relative relationship between an element and phenotypes. Given the wide variation in leaf tissue concentrations across all 16 cultivars, an overall consolidated data set was developed to provide a refinement of the leaf tissue nutrient standards for coleus across all elements. This expands the recommended ranges available for interpreting leaf tissue samples, which will assist growers and crop advisors in diagnosing nutrient disorders of coleus.